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University of Southern California
1.
Mylapilli, Harshavardhan.
An analytical dynamics approach to the control of mechanical
systems.
Degree: PhD, Aerospace and Mechanical Engineering (Dynamics and
Control), 2015, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/625018/rec/681 
► A new and novel approach to the control of nonlinear mechanical systems is presented in this study. The approach is inspired by recent results in…
(more)
▼ A new and novel approach to the control of nonlinear
mechanical systems is presented in this study. The approach is
inspired by recent results in analytical dynamics that deal with
the theory of constrained motion. The control requirements on the
dynamical system are viewed from an analytical dynamics perspective
and the theory of constrained motion is used to recast these
control requirements as constraints on the dynamical system.
Explicit closed form expressions for the generalized nonlinear
control forces are obtained by using the fundamental equation of
mechanics. The control so obtained is optimal at each instant of
time and causes the constraints to be exactly satisfied. No
linearizations and/or approximations of the nonlinear dynamical
system are made, and no a priori structure is imposed on the nature
of nonlinear controller. Three examples dealing with highly
nonlinear complex dynamical systems that are chosen from diverse
areas of discrete and continuum mechanics are presented to
demonstrate the control approach. The first example deals with the
energy control of underactuated inhomogeneous nonlinear lattices
(or chains), the second example deals with the synchronization of
the motion of multiple coupled slave gyros with that of a master
gyro, and the final example deals with the control of
incompressible hyperelastic rubber-like thin cantilever beams.
Numerical simulations accompanying these examples show the ease,
simplicity and the efficacy with which the control methodology can
be applied and the accuracy with which the desired control
objectives can be met.
Advisors/Committee Members: Udwadia, Firdaus Erach (Committee Chair), Sacker, Robert J. (Committee Member), Redekopp, Larry G. (Committee Member).
Subjects/Keywords: Fermi–Pasta–Ulam problem; nonlinear non-homogeneous chains; energy control; fundamental equation of mechanics; closed form global asymptotic control; solitons; breathers; Udwadia-Kalaba equation; multiple gyroscopes; synchronization; constrained motion; nonlinear control; chain-coupling; general-coupling; under actuation; hyperelastic materials; Mooney-Rivlin models; absolute nodal coordinate formulation (ANCF); incompressible material; Poisson volumetric locking; selective reduced integration; Störmer–Verlet method; thin beams; cantilever beams; beam control; nodal control
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APA (6th Edition):
Mylapilli, H. (2015). An analytical dynamics approach to the control of mechanical
systems. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/625018/rec/681
Chicago Manual of Style (16th Edition):
Mylapilli, Harshavardhan. “An analytical dynamics approach to the control of mechanical
systems.” 2015. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/625018/rec/681.
MLA Handbook (7th Edition):
Mylapilli, Harshavardhan. “An analytical dynamics approach to the control of mechanical
systems.” 2015. Web. 22 Jan 2021.
Vancouver:
Mylapilli H. An analytical dynamics approach to the control of mechanical
systems. [Internet] [Doctoral dissertation]. University of Southern California; 2015. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/625018/rec/681.
Council of Science Editors:
Mylapilli H. An analytical dynamics approach to the control of mechanical
systems. [Doctoral Dissertation]. University of Southern California; 2015. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/625018/rec/681
University of Southern California
2.
Son, Sangyoung.
Wave induced hydrodynamic complexity and transport in the
nearshore.
Degree: PhD, Civil Engineering, 2014, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/66462/rec/7876
► In the coastal area, defined as the region between the shoreline and some offshore limit where the depth can no longer influence the waves, complex…
(more)
▼ In the coastal area, defined as the region between the
shoreline and some offshore limit where the depth can no longer
influence the waves, complex behavior of waves is anticipated due
to various physical effects such as turbulence, wave-structure
interaction, wave-current interaction, wave breaking and
fluid-density variations. For modeling of nearshore hydrodynamics,
many numerical models have been developed so far, but many of such
effects are not yet considered appropriately. ❧ In this
dissertation, depth-integrated numerical models used in long wave
simulation are developed for better understanding of complicated
hydrodynamics at the nearshore. First, a non-dispersive shallow
water equation model and dispersive Boussinesq model are two-way
coupled. The fundamental purpose of the coupling effort is to
develop the capability to seamlessly model long wave evolution from
deep to shallow water with fine scale resolution, without the loss
of locally important physics. Second, a set of depthintegrated
equations describing combined wave-current flows are derived
mathematically and discretized numerically. To account for the
effect of turbulent interaction between waves and underlying
currents with arbitrary profile, new additional stresses are
introduced, which represent radiation stress of waves over the
ambient current field. Finally, a numerical model for gravity waves
propagating over variable density fluids is developed by allowing
horizontal and vertical variation of fluid density. Throughout the
derivation, density change effects appear as correction terms while
the internal wave effects on the free surface waves in a two-layer
system are accounted for through direct inclusion of the internal
wave velocity component. For each of the studied topics, numerical
tests are performed to support accuracy and applicability.
Consequently, we have developed a comprehensive tool for numerical
simulation of complex nearshore hydrodynamics.
Advisors/Committee Members: Lynett, Patrick J. (Committee Chair), Lee, Jiin-Jen (Committee Member), Redekopp, Larry G. (Committee Member).
Subjects/Keywords: turbulence; coherent structures; eddies; tsunami whirlpool; long waves; shallow water; transport; Boussinesq equations; nearshore; wave-current interactions; two-way coupling; stratified flows; internal waves; tsunami
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MLA ·
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APA (6th Edition):
Son, S. (2014). Wave induced hydrodynamic complexity and transport in the
nearshore. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/66462/rec/7876
Chicago Manual of Style (16th Edition):
Son, Sangyoung. “Wave induced hydrodynamic complexity and transport in the
nearshore.” 2014. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/66462/rec/7876.
MLA Handbook (7th Edition):
Son, Sangyoung. “Wave induced hydrodynamic complexity and transport in the
nearshore.” 2014. Web. 22 Jan 2021.
Vancouver:
Son S. Wave induced hydrodynamic complexity and transport in the
nearshore. [Internet] [Doctoral dissertation]. University of Southern California; 2014. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/66462/rec/7876.
Council of Science Editors:
Son S. Wave induced hydrodynamic complexity and transport in the
nearshore. [Doctoral Dissertation]. University of Southern California; 2014. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/66462/rec/7876
University of Southern California
3.
Chu, Hao-Kun.
Fluid dynamics of sessile drops in shear flows.
Degree: PhD, Mechanical Engineering, 2011, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/643541/rec/2851
► The shear flow dynamics of a viscous liquid drop placed in another fluid medium is analyzed in the Stokes-flow regime. This study is motivated by…
(more)
▼ The shear flow dynamics of a viscous liquid drop
placed in another fluid medium is analyzed in the Stokes-flow
regime. This study is motivated by investigations on protein
crystal growth for which it is known that shear flow in the protein
solution affects the nucleation rate. It is of interest to be able
to generate and control shear flow in the sessile-drop geometry
which is commonly used for crystal growth and protein aggregation
studies. While drops for such experiments are usually of the
spherical-cap shape, the enormous analytical complexity has led us
to first deal with a two-dimensional drop with linear shear in the
external medium, i.e., the cylindrical equivalent of the cap. With
the bipolar coordinate system, the circular interface can be
exactly identified by constant value of one of the coordinates, and
lends itself to satisfying the relevant continuity conditions at
the gas-liquid and the solid-liquid interfaces of the system. The
second case of a three-dimensional axisymmetric sessile drop with
extensional flow shear is analyzed under toroidal coordinate system
with the same advantage of fitting gas-liquid interface as bipolar
coordinate system. While these two cases rely on the mechanical
shear, a third case of electrostatically driven flow applied to a
hemispherical drop on a solid surface is also considered. The exact
solutions within the framework of Stokes flow of three cases are
developed, and the flow field and shear stress distribution are
rendered in this study. Some major effects of fluid properties,
such as viscosity ratio, and dielectric constant ratio, to shear
stress distributions are discussed. It is expected that the
quantitive evaluation of the parameters governing shear will
provide useful information for controlling shear rate in a sessile
drop. The analysis would be helpful in the design of experiments
where direct measurement of shear is generally intrusive and
possibly disruptive to other sensitive physicochemical processes
such as protein nucleation.
Advisors/Committee Members: Sadhal, Satwindar S. (Committee Chair), Redekopp, Larry G. (Committee Member), Shing, Katherine S. (Committee Member).
Subjects/Keywords: shear flow; extensional flow; electric shear; sessile drop; toroidal
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APA (6th Edition):
Chu, H. (2011). Fluid dynamics of sessile drops in shear flows. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/643541/rec/2851
Chicago Manual of Style (16th Edition):
Chu, Hao-Kun. “Fluid dynamics of sessile drops in shear flows.” 2011. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/643541/rec/2851.
MLA Handbook (7th Edition):
Chu, Hao-Kun. “Fluid dynamics of sessile drops in shear flows.” 2011. Web. 22 Jan 2021.
Vancouver:
Chu H. Fluid dynamics of sessile drops in shear flows. [Internet] [Doctoral dissertation]. University of Southern California; 2011. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/643541/rec/2851.
Council of Science Editors:
Chu H. Fluid dynamics of sessile drops in shear flows. [Doctoral Dissertation]. University of Southern California; 2011. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/643541/rec/2851
University of Southern California
4.
Sellappan, Prabu.
Wake modes of rotationally oscillating circular cylinder in
cross-flow and its relationship with heat transfer.
Degree: PhD, Mechanical Engineering, 2013, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/290445/rec/7865
► Wake formation is an important problem in engineering due to its effect on phenomena such as vortex induced vibrations and heat transfer. While prior work…
(more)
▼ Wake formation is an important problem in engineering
due to its effect on phenomena such as vortex induced vibrations
and heat transfer. While prior work has focused on the wake
formation due to vortex shedding from stationary, stream-wise, and
transversely oscillating cylinders, limited information is
available on the effect of rotary oscillations on wake formation.
The relationship between wake formation and heat transfer is also
not fully understood. Therefore, a series of experiments were
conducted to determine the effect of rotationally oscillating
cylinders on wake formation and its relationship with heat
transfer. ❧ Experiments were carried out at Re = 150 and 750 in a
water tunnel for oscillation frequencies from 0.67 to 3.5 times the
natural shedding frequency and peak-to-peak oscillation amplitudes
up to 320°. Experiments were performed at the lower Re using an
unheated cylinder. Two sets of experiments were performed at the
higher Re, one with the cylinder unheated and the other with the
cylinder heated. Digital Particle Image Velocimetry (DPIV) was used
to identify and map wake modes (coherent vortical structures in the
wake) to various regions of the parameter space. Previously unknown
wake modes that are synchronized over two and three times the
forcing frequency were also discovered. ❧ Experiments were also
performed at Re = 750 to measure the heat transfer rate for a large
number of cases in the parameter space. Significant heat transfer
enhancement was observed under certain forcing conditions and the
regions of the parameter space where this occurs was found to
correspond to locked-on wake mode regions. Other factors, such as
the tangential velocity and the formation length were also found to
affect the heat transfer under certain conditions.
Advisors/Committee Members: Spedding, Geoffrey R. (Committee Chair), Redekopp, Larry G. (Committee Member), Eliasson, Veronica (Committee Member), Becker, Thorsten W. (Committee Member).
Subjects/Keywords: DPIV; vortex shedding; wake formation; convective heat transfer; wake modes; rotary oscillations; fluid mechanics; separated flows
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APA (6th Edition):
Sellappan, P. (2013). Wake modes of rotationally oscillating circular cylinder in
cross-flow and its relationship with heat transfer. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/290445/rec/7865
Chicago Manual of Style (16th Edition):
Sellappan, Prabu. “Wake modes of rotationally oscillating circular cylinder in
cross-flow and its relationship with heat transfer.” 2013. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/290445/rec/7865.
MLA Handbook (7th Edition):
Sellappan, Prabu. “Wake modes of rotationally oscillating circular cylinder in
cross-flow and its relationship with heat transfer.” 2013. Web. 22 Jan 2021.
Vancouver:
Sellappan P. Wake modes of rotationally oscillating circular cylinder in
cross-flow and its relationship with heat transfer. [Internet] [Doctoral dissertation]. University of Southern California; 2013. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/290445/rec/7865.
Council of Science Editors:
Sellappan P. Wake modes of rotationally oscillating circular cylinder in
cross-flow and its relationship with heat transfer. [Doctoral Dissertation]. University of Southern California; 2013. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/290445/rec/7865
University of Southern California
5.
Orr, Trevor Stuart.
Numerical simulations of linearly stratified flow around a
sphere.
Degree: PhD, Aerospace and Mechanical Engineering (Computational
Fluid and Solid Mechanics), 2014, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/484651/rec/4490
► A numerical investigation of the near wake of a sphere moving horizontally through a linearly stratified fluid. Simulations are performed at a low Reynolds number…
(more)
▼ A numerical investigation of the near wake of a sphere
moving horizontally through a linearly stratified fluid.
Simulations are performed at a low Reynolds number of 200 for a
range of internal Froude number. Simulations at Reynolds number of
1000 across a range of Froude number greater than 1 provide a
description and parameterization of the near wake, including the
density field. The effects of utilizing two different averaging
techniques in the unsteady near wake region are discussed.
Perturbation quantities in the stratified near wake are
anisotropic, and the Froude number at which the stratified flow can
be treated as a uniform density fluid is suggested to be on the
order of 100. Parameterization of the near wake is accomplished
using the parameterized wake height, downstream distance from
sphere, and Froude number as parameters.
Advisors/Committee Members: Domaradzki, Julian A. (Committee Chair), Spedding, Geoffrey R. (Committee Member), Redekopp, Larry G. (Committee Member), Eliasson, Veronica (Committee Member), Nakano, Aiichiro (Committee Member).
Subjects/Keywords: stratified wakes; stratified near wake; stratified flow; near wake; non-equilibrium regime; NEQ regime; non-equilibrium region; NEQ region; pancake vortices; direct numerical simulation; direct numerical simulation of stratified flow; detached eddy simulation; sphere; wake; sphere wake; sphere wakes; density perturbation; density field; thermally stratified; linearly stratified; linearly stratified flow; Froude number; internal wave; vortex shedding; sphere-less initialization; spatial averaging; DPIV; wake parameterization; wake parametrization; anisotropic wake
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Manager
APA (6th Edition):
Orr, T. S. (2014). Numerical simulations of linearly stratified flow around a
sphere. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/484651/rec/4490
Chicago Manual of Style (16th Edition):
Orr, Trevor Stuart. “Numerical simulations of linearly stratified flow around a
sphere.” 2014. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/484651/rec/4490.
MLA Handbook (7th Edition):
Orr, Trevor Stuart. “Numerical simulations of linearly stratified flow around a
sphere.” 2014. Web. 22 Jan 2021.
Vancouver:
Orr TS. Numerical simulations of linearly stratified flow around a
sphere. [Internet] [Doctoral dissertation]. University of Southern California; 2014. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/484651/rec/4490.
Council of Science Editors:
Orr TS. Numerical simulations of linearly stratified flow around a
sphere. [Doctoral Dissertation]. University of Southern California; 2014. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/484651/rec/4490
University of Southern California
6.
Plocher, Dennis Alan.
Experimental investigation of spray development immediately
behind a tire rolling on a wet surface.
Degree: PhD, Aerospace Engineering, 2011, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/638947/rec/2630
► The spray pattern immediately behind a single-groove tire rolling on a wet surface is produced in the laboratory using a specially designed tire spray simulator.…
(more)
▼ The spray pattern immediately behind a single-groove
tire rolling on a wet surface is produced in the laboratory using a
specially designed tire spray simulator. The spray behavior is
examined using high speed video. To characterize how rapidly water
drains from the groove, a concept referred to as time-to-drain is
defined and a technique developed and demonstrated for its
measurement. ❧ The water-air interface in the groove of a rotating
tire feels an acceleration from the denser fluid into the less
dense fluid—the geometry of the Rayleigh-Taylor problem. Earlier
work (Browand, Plocher & Radovich 2010) observed a banded
structure downstream of the tire patch and suggested it was due to
the Rayleigh-Taylor instability. This present work examines that
suggestion by computing spectra from time series at different
points in the flow. Frequencies at spectral peaks are converted to
wavenumbers which are found to lie in the Rayleigh-Taylor unstable
band.
Advisors/Committee Members: Browand, Fredrick K. (Committee Chair), Spedding, Geoffrey R. (Committee Member), Redekopp, Larry G. (Committee Member), Lu, Stephen (Committee Member).
Subjects/Keywords: time-to-drain; tire spray; splash and spray; Rayleigh-Taylor instability
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APA (6th Edition):
Plocher, D. A. (2011). Experimental investigation of spray development immediately
behind a tire rolling on a wet surface. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/638947/rec/2630
Chicago Manual of Style (16th Edition):
Plocher, Dennis Alan. “Experimental investigation of spray development immediately
behind a tire rolling on a wet surface.” 2011. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/638947/rec/2630.
MLA Handbook (7th Edition):
Plocher, Dennis Alan. “Experimental investigation of spray development immediately
behind a tire rolling on a wet surface.” 2011. Web. 22 Jan 2021.
Vancouver:
Plocher DA. Experimental investigation of spray development immediately
behind a tire rolling on a wet surface. [Internet] [Doctoral dissertation]. University of Southern California; 2011. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/638947/rec/2630.
Council of Science Editors:
Plocher DA. Experimental investigation of spray development immediately
behind a tire rolling on a wet surface. [Doctoral Dissertation]. University of Southern California; 2011. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/638947/rec/2630
University of Southern California
7.
Yang, Shanling.
Boundary layer and separation control on wings at low
Reynolds numbers.
Degree: PhD, Aerospace Engineering, 2013, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/337675/rec/1157
► In the transitional chord-based Reynolds number regime for aeronautics, 10⁴ ≤ Re ≤ 10⁵, fluid flow over a surface is prone to separation followed by…
(more)
▼ In the transitional chord-based Reynolds number regime
for aeronautics, 10⁴ ≤ Re ≤ 10⁵, fluid flow over a surface is prone
to separation followed by possible reattachment and transition to
turbulence. The amplification of disturbances in the boundary layer
promotes transition to turbulence, so boundary layer and separation
control methods are especially favorable in this transitional Re
regime. The use of sound to control flow separation at transitional
and moderate Re for various smooth airfoils has been experimentally
studied in the literature. Optimum excitation frequencies are
reported to match the frequency or sub harmonics of the naturally
occurring instabilities in the shear layer, and correlations
between optimum frequencies for external acoustic forcing and
tunnel anti-resonances have been observed. However, reported
optimum frequency values based on the Strouhal number scaling
St/Re^(1/2) are not in complete agreement among the different
reported studies. Little attention has been given to distinguish
the effects of standing waves from traveling sound waves.
Mathematical and experimental studies of sound and boundary layer
instability interactions have also yielded mixed results,
suggesting that there still lacks a full understanding about the
mechanism by which acoustic waves affect boundary layer flows. ❧
Results on boundary layer and separation control through acoustic
excitation at low Re numbers are reported. The Eppler 387 profile
is specifically chosen because of its pre-stall hysteresis and
bi-stable state behavior in the transitional Re regime, which is a
result of flow separation and reattachment. External acoustic
forcing on the wing yields large improvements (more than 70%) in
lift-to-drag ratio and flow reattachment at forcing frequencies
that correlate with the measured anti-resonances in the wind
tunnel. The optimum St/Re^(1/2) range for Re = 60,000 matches the
proposed optimum range in the literature, but there is less
agreement for Re = 40,000, which suggests that correct St scaling
has not been determined. The correlation of aerodynamic
improvements to wind tunnel resonances implies that external
acoustic forcing is facility-dependent, which inhibits practical
application. Therefore, internal acoustic excitation for the same
wing profile is also pursued. ❧ Internal acoustic forcing is
designed to be accomplished by embedding small speakers inside a
custom-designed wing that contains many internal cavities and small
holes in the suction surface. However, initial testing of this
semi-porous wing model shows that the presence of the small holes
in the suction surface completely transforms the aerodynamic
performance by changing the mean chordwise separation location and
causing an originally separated, low-lift state flow to reattach
into a high-lift state. The aerodynamic improvements are not caused
by the geometry of the small holes themselves, but rather by
Helmholtz resonance that occurs in the cavities, which generate
tones that closely match the intrinsic flow instabilities.…
Advisors/Committee Members: Spedding, Geoffrey R. (Committee Chair), Redekopp, Larry G. (Committee Member), Eliasson, Veronica (Committee Member), Bickers, Gene (Committee Member), Radovich, Charles (Committee Member).
Subjects/Keywords: low Reynolds numbers; separation control; acoustic excitation; active separation control; passive separation control; boundary layers; fluid dynamics; aerodynamics; Helmholtz resonance; local acoustic forcing; external acoustic excitation; internal excitation; flow control
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APA ·
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MLA ·
Vancouver ·
CSE |
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to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Yang, S. (2013). Boundary layer and separation control on wings at low
Reynolds numbers. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/337675/rec/1157
Chicago Manual of Style (16th Edition):
Yang, Shanling. “Boundary layer and separation control on wings at low
Reynolds numbers.” 2013. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/337675/rec/1157.
MLA Handbook (7th Edition):
Yang, Shanling. “Boundary layer and separation control on wings at low
Reynolds numbers.” 2013. Web. 22 Jan 2021.
Vancouver:
Yang S. Boundary layer and separation control on wings at low
Reynolds numbers. [Internet] [Doctoral dissertation]. University of Southern California; 2013. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/337675/rec/1157.
Council of Science Editors:
Yang S. Boundary layer and separation control on wings at low
Reynolds numbers. [Doctoral Dissertation]. University of Southern California; 2013. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/337675/rec/1157
University of Southern California
8.
Sheikhhassani, Ramtin.
Scattering of a plane harmonic SH-wave and dynamic stress
concentration for multiple multilayered inclusions embedded in an
elastic half-space.
Degree: PhD, Mechanical Engineering, 2015, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/558014/rec/5698
► The scattering of a plane harmonic SH-wave by an arbitrary number of layered inclusions in a half-space is investigated bya direct boundary integral equation method.…
(more)
▼ The scattering of a plane harmonic SH-wave by an
arbitrary number of layered inclusions in a half-space is
investigated bya direct boundary integral equation method. The
inclusions, which have arbitrary shape and arrangement, are
embedded within an elastic half-space. The effects of multiple
scattering, the geometry, and the impedance contrast of the
materials for layered inclusions and pipes, on the surface motion,
are considered in detail. ❧ Additionally, a non-hypersingular
technique is employed to calculate the dynamic stress concentration
factor along the interfaces of inclusions. Various contributing
factors that can influence the stress concentration, including
multiple scattering, the impedance contrast of layers, and the
separation distance between the scatterers, are investigated. The
numerical results are presented for a wide range of parameters
present in the problem.
Advisors/Committee Members: Dravinski, Marijan (Committee Chair), Sadhal, Satwindar S. (Committee Member), Redekopp, Larry G. (Committee Member), Lee, Vincent W. (Committee Member).
Subjects/Keywords: multiple scattering; dynamic stress concentration factor; wave propagation; layered inclusions; elastic waves; anti-plane strain; non-hypersingular boundary element method
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APA (6th Edition):
Sheikhhassani, R. (2015). Scattering of a plane harmonic SH-wave and dynamic stress
concentration for multiple multilayered inclusions embedded in an
elastic half-space. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/558014/rec/5698
Chicago Manual of Style (16th Edition):
Sheikhhassani, Ramtin. “Scattering of a plane harmonic SH-wave and dynamic stress
concentration for multiple multilayered inclusions embedded in an
elastic half-space.” 2015. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/558014/rec/5698.
MLA Handbook (7th Edition):
Sheikhhassani, Ramtin. “Scattering of a plane harmonic SH-wave and dynamic stress
concentration for multiple multilayered inclusions embedded in an
elastic half-space.” 2015. Web. 22 Jan 2021.
Vancouver:
Sheikhhassani R. Scattering of a plane harmonic SH-wave and dynamic stress
concentration for multiple multilayered inclusions embedded in an
elastic half-space. [Internet] [Doctoral dissertation]. University of Southern California; 2015. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/558014/rec/5698.
Council of Science Editors:
Sheikhhassani R. Scattering of a plane harmonic SH-wave and dynamic stress
concentration for multiple multilayered inclusions embedded in an
elastic half-space. [Doctoral Dissertation]. University of Southern California; 2015. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/558014/rec/5698
University of Southern California
9.
Ghaemi Oskouei, Babak.
Stability of body-vortex systems: Application to aquatic
locomotion.
Degree: PhD, Aerospace & Mechanical Engineering (Dynamics &
Control), 2013, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/451808/rec/6029
► Mathematical modeling and analysis of biological systems such as swimming and flying is an interdisciplinary research field with an extensive range of applications including the…
(more)
▼ Mathematical modeling and analysis of biological
systems such as swimming and flying is an interdisciplinary
research field with an extensive range of applications including
the design of unmanned underwater robots and swarm of robots that
swim together in a coordinated way similar to schooling fish. One
of the main objectives of our work is to develop mathematical
models for certain aspect of schooling. In particular, we examine
(1) the interaction of a single fish with ambient vorticity
possibly generated by other neighboring fish; and (2) the
interaction of multiple fish wakes in large fish schools.; For the
first part, we propose a reduced model of a rigid body interacting
with point vortices in potential fluid and demonstrate that the
rigid body can swim upstream in the direction opposite to the
motion of point vortices at no energy cost. Indeed, the rigid body
itself does not generate any force and its motion is due entirely
to the energy exploited from the presence of the point vortices. We
comment on the stability of these motions and propose
under-actuated active control methods to achieve locomotion in
unsteady wakes.; In the second part, we consider the interaction of
multiple reverse von K´arm´an vortex streets as a model of the
mid-wake region of large fish schools. We focus on the wake
dynamics to gain insight into the role of the fluid in transporting
oxygen and nutrients to inner fish as well as its role in
facilitating or acting as flow barriers to passive locomotion.; We
examine the topology of the streamline patterns in a frame moving
with the same translational velocity as the streets which lends
insight into fluid transport through the mid-wake
region.
Advisors/Committee Members: Kanso, Eva (Committee Chair), Newton, Paul K. (Committee Member), Redekopp, Larry G. (Committee Member), Mitra, Urbashi (Committee Member).
Subjects/Keywords: point vortex; dynamical systems; stability analysis; vortex wake; fish; fish schooling; solid body; fluid; interaction; floquet theory; inviscid; incompressible; irrotational flow; 2D flow; ellipse; circle; Kirchhoff Routh; classical; Milne Thomson; circle theorem; complex potential; velocity; kinematics; submerged; Grobli; periodic; thrust; drag; von Karman; street; mid wake; streamline; pattern; topology; time scale; bifurcation; Doubly-Infinite Array; zeta function; vortex lattice; orientation control; elongated body; staggered street; symmetric street; convergence; integral test; dynamics; control; ideal fluid; aquatic locomotion; propulsion
Record Details
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Ghaemi Oskouei, B. (2013). Stability of body-vortex systems: Application to aquatic
locomotion. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/451808/rec/6029
Chicago Manual of Style (16th Edition):
Ghaemi Oskouei, Babak. “Stability of body-vortex systems: Application to aquatic
locomotion.” 2013. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/451808/rec/6029.
MLA Handbook (7th Edition):
Ghaemi Oskouei, Babak. “Stability of body-vortex systems: Application to aquatic
locomotion.” 2013. Web. 22 Jan 2021.
Vancouver:
Ghaemi Oskouei B. Stability of body-vortex systems: Application to aquatic
locomotion. [Internet] [Doctoral dissertation]. University of Southern California; 2013. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/451808/rec/6029.
Council of Science Editors:
Ghaemi Oskouei B. Stability of body-vortex systems: Application to aquatic
locomotion. [Doctoral Dissertation]. University of Southern California; 2013. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/451808/rec/6029
University of Southern California
10.
Jing, Fangxu.
Part I: Viscous evolution of point vortex equilibria; Part
II: Effects of body elasticity on stability of fish motion.
Degree: PhD, Aerospace Engineering, 2011, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/652897/rec/4933
► Vortex dynamics and solid-fluid interactions are two of the most important and most studied topics in fluid dynamics for their relevance to a wide range…
(more)
▼ Vortex dynamics and solid-fluid interactions are two
of the most important and most studied topics in fluid dynamics for
their relevance to a wide range of applications from geophysical
flows to locomotion in moving fluids. In this work, we investigate
two problems in two parts: Part I studies the viscous evolution of
point vortex equilibria; Part II studies the effects of body
elasticity on the passive stability of submerged bodies. ❧ In Part
I, we describe the viscous evolution of point vortex configurations
that, in the absence of viscosity, are in a state of fixed or
relative equilibrium. In particular, we examine four cases, three
of them correspond to relative equilibria in the inviscid point
vortex model and one corresponds to a fixed equilibrium. Our goal
is to elucidate the dominant transient dynamical features of the
flow. A multi- Gaussian “core growing” type of model is typically
used in high fidelity numerical simulations, but we propose to
implement it as a low-order model for the flow field. We show that
all four configurations immediately begin to rotate unsteadily. We
then examine in detail the qualitative and quantitative evolution
of the structures as they evolve, and for each case show the
sequence of topological bifurcations that occur both in a fixed
reference frame, and in an appropriately chosen rotating reference
frame. Comparisons between the cases help to reveal different
features of the viscous evolution for short and intermediate time
scales of vortex structures. We examine the dynamical evolution of
passive particles in the viscously evolving flows and interpret it
in relation to the evolving streamline patterns. Although the
low-order multi-Gaussian model does not exactly coincide with the
Navier-Stokes solution, the two results show remarkable
resemblances in many aspects. ❧ In Part II, we examine the effects
of body geometry and elasticity on the passive stability of motion
in a perfect fluid. Our main motivation is to understand the role
of body elasticity on the stability of fish swimming. The fish is
modeled as an articulated body made of N links (assumed to be
identical ellipses in 2D or identical ellipsoids in 3D)
interconnected by hinge joints. It can undergo shape changes by
varying the relative angles between the links. Body elasticity is
accounted for via the torsional springs at the joints. The
unsteadiness of the flow is modeled using the added mass effect.
Equations of motion for the body-fluid system are derived using
Newtonian and Lagrangian approaches for both hydrodynamically
decoupled and coupled models in 2D and 3D. We specifically examine
the stability associated with a relative equilibrium of the
equations, traditionally referred to as the “coast motion” (proved
to be unstable for a rigid elongated body model), and found that
body elasticity does stabilize the system. Stable regions are
identified based on linear stability analysis in the parameter
space spanned by aspect ratio (body geometry) and spring constants
(muscle stiffness), and the findings based on the…
Advisors/Committee Members: Kanso, Eva (Committee Chair), Newton, Paul K. (Committee Member), Flashner, Henryk (Committee Member), Friedlander, Susan (Committee Member), Redekopp, Larry G. (Committee Member).
Subjects/Keywords: vortex dynamics; fish stability
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Jing, F. (2011). Part I: Viscous evolution of point vortex equilibria; Part
II: Effects of body elasticity on stability of fish motion. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/652897/rec/4933
Chicago Manual of Style (16th Edition):
Jing, Fangxu. “Part I: Viscous evolution of point vortex equilibria; Part
II: Effects of body elasticity on stability of fish motion.” 2011. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/652897/rec/4933.
MLA Handbook (7th Edition):
Jing, Fangxu. “Part I: Viscous evolution of point vortex equilibria; Part
II: Effects of body elasticity on stability of fish motion.” 2011. Web. 22 Jan 2021.
Vancouver:
Jing F. Part I: Viscous evolution of point vortex equilibria; Part
II: Effects of body elasticity on stability of fish motion. [Internet] [Doctoral dissertation]. University of Southern California; 2011. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/652897/rec/4933.
Council of Science Editors:
Jing F. Part I: Viscous evolution of point vortex equilibria; Part
II: Effects of body elasticity on stability of fish motion. [Doctoral Dissertation]. University of Southern California; 2011. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/652897/rec/4933
University of Southern California
11.
Reddy, Shalini A.
Control of spacecraft with flexible structures using
pulse-modulated thrusters.
Degree: PhD, Mechanical Engineering, 2012, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/84663/rec/1641
► A methodology for the design of robust control systems for flexible spacecraft undergoing a large angle maneuver using pulse-modulated thrusters is proposed. The need for…
(more)
▼ A methodology for the design of robust control systems
for flexible spacecraft undergoing a large angle maneuver using
pulse-modulated thrusters is proposed. The need for developing such
a methodology stems from the need to reduce the weight of the
modern spacecraft and to satisfy strict performance specifications
resulting in vibrational modes within the control system bandwidth.
Moreover, the discontinuous operation of pulse-modulation may
excite large flexible motion that can lead to deterioration of
performance, limit cycles, and even instability. Consequently, the
current practice of designing the control system using a rigid body
model and evaluating performance by simulation using a flexible
model is inadequate for the modern spacecraft. In the proposed
methodology structural flexibility is included in the control
design model thus resulting in control systems with robust
stability and improved performance. ❧ This dissertation has two
main parts: formulation of flexible spacecraft dynamics performing
large angle motion and control system design. The formulation of
equations of motion is performed using quasi-coordinates that allow
for parameterization of the attitude in terms of Euler-Rodrigues
parameters that avoid singularities. Moreover, the formulation is
in terms of variables measurable by the control system, such as
angular velocities and is in a form that is convenient for
establishing closed-loop robust stability. The control law
structure proposed here results in guaranteed closed-loop
performance in the presence of parameter uncertainties, measurement
noise, and command implementation errors. A theorem that guarantees
the bounds of trajectory following errors of a spacecraft
performing a general translational and rotational motion in
three-dimensional space is formulated and proven using Lyapunov
stability theory. Finally, a model of a flexible spacecraft is used
to demonstrate the performance of a control system developed using
the proposed methodology are presented. A number of different
maneuvers are studied by simulation showing satisfactory
performance in the presence of uncertainties and implementation
errors.
Advisors/Committee Members: Flashner, Henryk (Committee Chair), Redekopp, Larry G. (Committee Member), Shiflett, Geoffrey R. (Committee Member), Yang, Bingen (Ben) (Committee Member), Kukavica, Igor (Committee Member).
Subjects/Keywords: spacecraft; dynamics; control
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Reddy, S. A. (2012). Control of spacecraft with flexible structures using
pulse-modulated thrusters. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/84663/rec/1641
Chicago Manual of Style (16th Edition):
Reddy, Shalini A. “Control of spacecraft with flexible structures using
pulse-modulated thrusters.” 2012. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/84663/rec/1641.
MLA Handbook (7th Edition):
Reddy, Shalini A. “Control of spacecraft with flexible structures using
pulse-modulated thrusters.” 2012. Web. 22 Jan 2021.
Vancouver:
Reddy SA. Control of spacecraft with flexible structures using
pulse-modulated thrusters. [Internet] [Doctoral dissertation]. University of Southern California; 2012. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/84663/rec/1641.
Council of Science Editors:
Reddy SA. Control of spacecraft with flexible structures using
pulse-modulated thrusters. [Doctoral Dissertation]. University of Southern California; 2012. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/84663/rec/1641
University of Southern California
12.
Wang, Chuanxi.
Converging shocks in water and material effects.
Degree: PhD, Physics, 2013, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/338110/rec/1655
► During events of underwater explosions, the resulting shock waves poses extreme mechanical loadings to the nearby naval structures. Therefore this dissertation studies the shock wave…
(more)
▼ During events of underwater explosions, the resulting
shock waves poses extreme mechanical loadings to the nearby naval
structures. Therefore this dissertation studies the shock wave
dynamics of water inside a solid structure and the dynamical
response of such a structure. The goal is to understand the effect
of underwater shock wave focusing on materials possessing various
mechanical properties with an emphasis on lightweight materials.
This research has a direct impact on the material selection and
hydrodynamic considerations in naval architecture. ❧ Two steps are
taken towards the research goal. First, a special geometry of the
confinement structure called logarithmic spiral is chosen. This
type of shape will help to focus the shock wave, which will yield
the maximum energy at the focal region. Numerical simulations are
conducted to confirm the derived characteristics of the geometry.
When including weak material coupling with the liquid, both
experiments and simulations demonstrate that the shock dynamics in
water is sensitive to the coupling. ❧ Secondly, significant
coupling effect is introduced by reducing the thickness of the
solid structure. Experimental and numerical investigations are both
carried out to shed light onto the details of the fluid-structure
coupling. The results revealed that the thickness of the material
has the most significant impact on both the fluid dynamics and the
deformation mechanisms of the structure. Lightweight carbon fiber
composite structures are also studied under the same framework. ❧
Along the way, this dissertation also proposes and designs
experimental methodologies to enable the study of highly dynamic
underwater events.
Advisors/Committee Members: Eliasson, Veronica (Committee Chair), Haas, Stephan W. (Committee Member), Dappen, Werner (Committee Member), Däppen, Werner (Committee Member), Daeppen, Werner (Committee Member), Thompson, Richard S. (Committee Member), Redekopp, Larry G. (Committee Member).
Subjects/Keywords: shock focusing; underwater explosion; fluid-structure interaction; Schlieren optics
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wang, C. (2013). Converging shocks in water and material effects. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/338110/rec/1655
Chicago Manual of Style (16th Edition):
Wang, Chuanxi. “Converging shocks in water and material effects.” 2013. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/338110/rec/1655.
MLA Handbook (7th Edition):
Wang, Chuanxi. “Converging shocks in water and material effects.” 2013. Web. 22 Jan 2021.
Vancouver:
Wang C. Converging shocks in water and material effects. [Internet] [Doctoral dissertation]. University of Southern California; 2013. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/338110/rec/1655.
Council of Science Editors:
Wang C. Converging shocks in water and material effects. [Doctoral Dissertation]. University of Southern California; 2013. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/338110/rec/1655
University of Southern California
13.
Tantikul, Tawan.
Truncated Navier-Stokes equations with the automatic
filtering criterion.
Degree: PhD, Aerospace Engineering, 2011, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/619591/rec/7619
► A Large Eddy Simulation (LES) methodology based on previously developed Truncated Navier Stokes (TNS) approach is proposed. In TNS, the Navier Stokes equations are solved…
(more)
▼ A Large Eddy Simulation (LES) methodology based on
previously developed Truncated Navier Stokes (TNS) approach is
proposed. In TNS, the Navier Stokes equations are solved through a
sequence of direct numerical simulation runs and a periodical
processing of small scales to provide the necessary dissipation. In
the simplest case, the processing is accomplished by filtering the
turbulent fields with a properly chosen filter. In the previous
approach, the period for processing was selected in advance for
each case using heuristic arguments validated by trial and error.
In this proposed model, the filtering criterion is developed to
automate the selection of time instant in simulations when the
processing is needed. The criterion is based on the relationship
between the energy of the flow field and the energy of the same
field filtered with the chosen filter. Numerical experiments were
conducted to validate this model by comparing the computed low
order statistics in fully developed channel flows at low to
moderate friction Reynolds numbers with the benchmark data. An
analysis of the preliminary results showed that in wall resolved
LES the results are independent of the value of the filtering
criterion as long as it falls into the derived guideline range. To
achieve an improvement of the model's predictability, Reynolds
stress and energy budgets in the simulations performed with this
model were analyzed. They led to better understanding of filtering
effects on the energy transport and suggested how the filtering can
be modified to manipulate the energy content in specific areas of
the flow. Such selective filtering procedures improve results in
marginally resolved LES and can be applied to transitional
flows.
Advisors/Committee Members: Domaradzki, Julian Andrzej (Committee Chair), Redekopp, Larry G. (Committee Member), Sadhal, Satwindar S. (Committee Member), Pottebaum, Tait Sherman (Committee Member), Lee, Jiin-Jen (Committee Member).
Subjects/Keywords: DNS; explicit filtering; LES; Turbulence
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Tantikul, T. (2011). Truncated Navier-Stokes equations with the automatic
filtering criterion. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/619591/rec/7619
Chicago Manual of Style (16th Edition):
Tantikul, Tawan. “Truncated Navier-Stokes equations with the automatic
filtering criterion.” 2011. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/619591/rec/7619.
MLA Handbook (7th Edition):
Tantikul, Tawan. “Truncated Navier-Stokes equations with the automatic
filtering criterion.” 2011. Web. 22 Jan 2021.
Vancouver:
Tantikul T. Truncated Navier-Stokes equations with the automatic
filtering criterion. [Internet] [Doctoral dissertation]. University of Southern California; 2011. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/619591/rec/7619.
Council of Science Editors:
Tantikul T. Truncated Navier-Stokes equations with the automatic
filtering criterion. [Doctoral Dissertation]. University of Southern California; 2011. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/619591/rec/7619
University of Southern California
14.
Cadieux, Francois.
Large eddy simulations of laminar separation bubble
flows.
Degree: PhD, Aerospace and Mechanical Engineering (Computational
Fluid and Solid Mechanics), 2015, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/553536/rec/3741
► The flow over blades and airfoils at moderate angles of attack and Reynolds numbers ranging from 10⁴ to 10⁵ undergoes separation due to the adverse…
(more)
▼ The flow over blades and airfoils at moderate angles
of attack and Reynolds numbers ranging from 10⁴ to 10⁵ undergoes
separation due to the adverse pressure gradient generated by
surface curvature. In many cases, the separated shear layer then
transitions to turbulence and reattaches, closing off a
recirculation region—the laminar separation bubble. To avoid
body‐fitted mesh generation problems and numerical issues, an
equivalent problem for flow over a flat plate is formulated by
imposing boundary conditions that lead to a pressure distribution
and Reynolds number that are similar to those on airfoils. Spalart
& Strelets (2000) tested a number of Reynolds‐averaged
Navier‐Stokes (RANS) turbulence models for a laminar separation
bubble flow over a flat plate. Although results with the
Spalart‐Allmaras turbulence model were encouraging, none of the
turbulence models tested reliably recovered time‐averaged direct
numerical simulation (DNS) results. The purpose of this work is to
assess whether large eddy simulation (LES) can more accurately and
reliably recover DNS results using drastically reduced
resolution—on the order of 1% of DNS resolution which is commonly
achievable for LES of turbulent channel flows. LES of a laminar
separation bubble flow over a flat plate are performed using a
compressible sixth‐order finite‐difference code and two
incompressible pseudo‐spectral Navier‐Stokes solvers at resolutions
corresponding to approximately 3% and 1% of the chosen DNS
benchmark by Spalart & Strelets (2000). The finite‐difference
solver is found to be dissipative due to the use of a
stability‐enhancing filter. Its numerical dissipation is quantified
and found to be comparable to the average eddy viscosity of the
dynamic Smagorinsky model, making it difficult to separate the
effects of filtering versus those of explicit subgrid‐scale
modeling. The negligible numerical dissipation of the
pseudo‐spectral solvers allows an unambiguous assessment of the
performance of subgrid‐scale models. Three explicit subgrid‐scale
models—dynamic Smagorinsky, σ, and truncated Navier‐Stokes
(TNS)—are compared to a no‐model simulation (under‐resolved DNS)
and evaluated against the benchmark DNS data focusing on two
quantities of critical importance to airfoil and blade designers:
time‐averaged pressure and skin friction predictions used in lift
and drag calculations. Results obtained with these explicit
subgrid‐scale models confirm that accurate LES of laminar
separation bubble flows are attainable with as low as 1% of DNS
resolution, and the poor performance of the no‐model simulation
underscores the necessity of subgrid‐scale modelling in coarse LES
with low numerical dissipation.
Advisors/Committee Members: Domaradzki, Julian A. (Committee Chair), Spedding, Geoffrey R. (Committee Member), Redekopp, Larry G. (Committee Member), Lynett, Patrick J. (Committee Member), Becker, Thorsten W. (Committee Member).
Subjects/Keywords: computational fluid dynamics; fluid mechanics; direct numerical simulation; large eddy simulation; turbomachinery; UAV
Record Details
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Cadieux, F. (2015). Large eddy simulations of laminar separation bubble
flows. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/553536/rec/3741
Chicago Manual of Style (16th Edition):
Cadieux, Francois. “Large eddy simulations of laminar separation bubble
flows.” 2015. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/553536/rec/3741.
MLA Handbook (7th Edition):
Cadieux, Francois. “Large eddy simulations of laminar separation bubble
flows.” 2015. Web. 22 Jan 2021.
Vancouver:
Cadieux F. Large eddy simulations of laminar separation bubble
flows. [Internet] [Doctoral dissertation]. University of Southern California; 2015. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/553536/rec/3741.
Council of Science Editors:
Cadieux F. Large eddy simulations of laminar separation bubble
flows. [Doctoral Dissertation]. University of Southern California; 2015. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll3/id/553536/rec/3741
University of Southern California
15.
Gates, Wess.
A simulation of particle dynamics in a two dimensional fluid
body under the influence of standing gravity waves.
Degree: MS, Aerospace & Mechanical Engineering (Computational
Fluid & Solid Mechanics), 2007, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/593725/rec/359
► An overview of the equations governing surface gravity waves in linear water wave theory is presented. These equations are used to derive an expression for…
(more)
▼ An overview of the equations governing surface gravity
waves in linear water wave theory is presented. These equations are
used to derive an expression for the stream function for standing
gravity waves in a two dimensional water body of uniform depth H.
Derivatives of the stream function yield a system of coupled
ordinary differential equations describing the particle velocities
tangent to the stream function everywhere inside the water body
boundaries.; Matlab and Simulink are used to numerically integrate
the velocity equations for particle position within the boundary.
The solutions presented describe the motion of a single particle
for varying initial conditions within the boundary. The simulation
is extended to test a two mode superposition for the system of
equations, for the same set of boundary conditions, in an effort to
understand the system behavior for various modes of standing
gravity waves.
Advisors/Committee Members: Newton, Paul K. (Committee Chair), Redekopp, Larry G. (Committee Member), Pottebaum, Tait Sherman (Committee Member).
Subjects/Keywords: standing gravity waves; two dimensional fluid body
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APA (6th Edition):
Gates, W. (2007). A simulation of particle dynamics in a two dimensional fluid
body under the influence of standing gravity waves. (Masters Thesis). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/593725/rec/359
Chicago Manual of Style (16th Edition):
Gates, Wess. “A simulation of particle dynamics in a two dimensional fluid
body under the influence of standing gravity waves.” 2007. Masters Thesis, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/593725/rec/359.
MLA Handbook (7th Edition):
Gates, Wess. “A simulation of particle dynamics in a two dimensional fluid
body under the influence of standing gravity waves.” 2007. Web. 22 Jan 2021.
Vancouver:
Gates W. A simulation of particle dynamics in a two dimensional fluid
body under the influence of standing gravity waves. [Internet] [Masters thesis]. University of Southern California; 2007. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/593725/rec/359.
Council of Science Editors:
Gates W. A simulation of particle dynamics in a two dimensional fluid
body under the influence of standing gravity waves. [Masters Thesis]. University of Southern California; 2007. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/593725/rec/359
University of Southern California
16.
Basilio, Ralph Ramos.
Controlled and uncontrolled motion in the circular,
restricted three-body problem: dynamically-natural spacecraft
formations.
Degree: PhD, Aerospace Engineering, 2007, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/500238/rec/1644
► Spacecraft formation flying involves operating multiple spacecraft in a pre-determined geometrical shape such that the configuration yields both individual and system benefits. One example is…
(more)
▼ Spacecraft formation flying involves operating
multiple spacecraft in a pre-determined geometrical shape such that
the configuration yields both individual and system benefits. One
example is an over-flight of the same spatial position by
spacecraft in geocentric orbit with the intent to create a
complementary data set of remotely sensed observables. Another
example is controlling to a high degree of accuracy the distance
between spacecraft in heliocentric orbit to create a virtual,
large-diameter interferometer telescope. Although Keplerian orbits
provide the basic framework for general and precision spacecraft
formation flying they also present limitations. Spacecraft are
generally constrained to operate only in circular and elliptical
orbits, parabolic paths, or hyperbolic trajectories around
celestial bodies. Applying continuation methods and bifurcation
theory techniques to the circular, restricted three-body problem –
where stable and unstable periodic orbits exist around equilibrium
points – creates an environment that is more orbit rich. After
surmounting a similar challenge with test particles in the
circular, restricted three-vortex problem in fluid mechanics as a
proof-of-concept, it was shown that spacecraft traveling in
uncontrolled motion along separate and distinct planar or
three-dimensional periodic orbits could be placed in controlled
motion, i.e. a controller is enabled and later disabled at
precisely the proper positions, to have them phase-locked on a
single periodic orbit. Although it was possible to use this
controller in a resonant frequency/orbit approach to establish a
formation, it was clearly shown that a separate controller could be
used in conjunction with the first to expedite the formation
establishment process.; Creation of these dynamically natural
spacecraft formations or multi-spacecraft platforms will enable the
'loiter, synchronize/coordinate, and observe' approach for future
engineering and scientific missions where flexibility is a
top-level requirement and key to mission success.
Advisors/Committee Members: Newton, Paul K. (Committee Chair), Baxendale, Peter H. (Committee Member), Redekopp, Larry G. (Committee Member).
Subjects/Keywords: dynamics; spacecraft; formations
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Basilio, R. R. (2007). Controlled and uncontrolled motion in the circular,
restricted three-body problem: dynamically-natural spacecraft
formations. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/500238/rec/1644
Chicago Manual of Style (16th Edition):
Basilio, Ralph Ramos. “Controlled and uncontrolled motion in the circular,
restricted three-body problem: dynamically-natural spacecraft
formations.” 2007. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/500238/rec/1644.
MLA Handbook (7th Edition):
Basilio, Ralph Ramos. “Controlled and uncontrolled motion in the circular,
restricted three-body problem: dynamically-natural spacecraft
formations.” 2007. Web. 22 Jan 2021.
Vancouver:
Basilio RR. Controlled and uncontrolled motion in the circular,
restricted three-body problem: dynamically-natural spacecraft
formations. [Internet] [Doctoral dissertation]. University of Southern California; 2007. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/500238/rec/1644.
Council of Science Editors:
Basilio RR. Controlled and uncontrolled motion in the circular,
restricted three-body problem: dynamically-natural spacecraft
formations. [Doctoral Dissertation]. University of Southern California; 2007. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/500238/rec/1644
University of Southern California
17.
Shokraneh, Houman.
N-vortex problem on a rotating sphere.
Degree: PhD, Mechanical Engineering, 2007, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/598303/rec/4315
► The evolution, interaction, and scattering of 2N-point vortices grouped into equal and opposite pairs (N-dipoles) on a rotating unit sphere is studied. A new coordinate…
(more)
▼ The evolution, interaction, and scattering of 2N-point
vortices grouped into equal and opposite pairs (N-dipoles) on a
rotating unit sphere is studied. A new coordinate system made up of
the centers-of-vorticity and centroids associated with each dipole
is introduced. With these coordinates, the nonlinear equations for
an isolated dipole diagonalize and one directly obtains the
equation for geodesic motion on the sphere for the dipole centroid.
When two or more dipoles interact, the equations are viewed as an
interacting billiard system on the sphere – charged billiards –
with long range interactions causing the centroid trajectories to
deviate from their geodesic paths. Canonical interactions are
studied both with and without rotation. For two dipoles, the four
basic interactions are described as exchange scattering,
non-exchange scattering, loop scattering (head-on) and loop
scattering (chasing) interactions. For three or more dipoles, one
obtains a richer variety of interactions, although the interactions
identified in the two-dipole case remain fundamental.
Advisors/Committee Members: Newton, Paul K. (Committee Chair), Redekopp, Larry G. (Committee Member), Ziane, Mohammed (Committee Member).
Subjects/Keywords: N-vortex problem; dipole scattering; charged billiard equations
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Shokraneh, H. (2007). N-vortex problem on a rotating sphere. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/598303/rec/4315
Chicago Manual of Style (16th Edition):
Shokraneh, Houman. “N-vortex problem on a rotating sphere.” 2007. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/598303/rec/4315.
MLA Handbook (7th Edition):
Shokraneh, Houman. “N-vortex problem on a rotating sphere.” 2007. Web. 22 Jan 2021.
Vancouver:
Shokraneh H. N-vortex problem on a rotating sphere. [Internet] [Doctoral dissertation]. University of Southern California; 2007. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/598303/rec/4315.
Council of Science Editors:
Shokraneh H. N-vortex problem on a rotating sphere. [Doctoral Dissertation]. University of Southern California; 2007. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/598303/rec/4315
University of Southern California
18.
Chen, Cheng-Yuan Jerry.
Multiple degree of freedom inverted pendulum dynamics:
modeling, computation, and experimentation.
Degree: PhD, Aerospace & Mechanical Engineering (Dynamics &
Control), 2009, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/238695/rec/4275
► A pendulum is statically unstable in its upright inverted state due to the Earth's gravitional attraction which points downward. However, with proper forcing, the pendulum…
(more)
▼ A pendulum is statically unstable in its upright
inverted state due to the Earth's gravitional attraction which
points downward. However, with proper forcing, the pendulum can be
stabilized in its upright inverted state. Special interest is on
periodic vertical forcing applied to the pendulum's base to
stabilize it around the upright inverted equilibrium. Many
researchers have studied how to stabilize the system by varying
various parameters, in particular its amplitude and frequency. Most
have focused on the single degree of freedom inverted pendulum
case, which with linear assumption can be described via Mathieu's
equation. The system stability can then be characterized by Floquet
theory. Our focus is on searching for the periodic solutions inside
the linearly stable region of the pendulum's inverted state when
the pendulum is under proper periodic forcing. Our research shows
that under appropriate excitation by controlling the forcing
amplitude and frequency, the pendulum can maintain certain periodic
orbits around its inverted state which we characterize in a
systematic way.; In this thesis, we applied four different kinds of
geometric realizations of the system response: system time traces,
system phase portraits, three dimensional views of the system phase
portrait as a function of input forcing, and the system's power
spectral density diagram. By analyzing these four diagrams
simultaneously, we characterize different kinds of multi-frequency
periodic behavior around the pendulum's inverted state. To further
discuss the effect of the nonlinearity, we applied perturbation
techniques using the normalized forcing amplitude as a perturbation
parameter to carry out the approximate periodic solutions on a
single degree of freedom inverted pendulum nonlinear model.; We
also discuss the multiple degree of freedom inverted pendulum
system. Both numerical simulation and experiments were performed
and detailed comparisons are discussed. Our numerical simulations
show close qualitative agreement with experiments.
Advisors/Committee Members: Newton, Paul K. (Committee Chair), Redekopp, Larry G. (Committee Member), Flashner, Henryk (Committee Member), Jonckheere, Edmond A. (Committee Member).
Subjects/Keywords: inverted pendulum; nonlinear dynamics; parametric excitation; Mathieu'; s equation; Floquet theory
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Chen, C. J. (2009). Multiple degree of freedom inverted pendulum dynamics:
modeling, computation, and experimentation. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/238695/rec/4275
Chicago Manual of Style (16th Edition):
Chen, Cheng-Yuan Jerry. “Multiple degree of freedom inverted pendulum dynamics:
modeling, computation, and experimentation.” 2009. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/238695/rec/4275.
MLA Handbook (7th Edition):
Chen, Cheng-Yuan Jerry. “Multiple degree of freedom inverted pendulum dynamics:
modeling, computation, and experimentation.” 2009. Web. 22 Jan 2021.
Vancouver:
Chen CJ. Multiple degree of freedom inverted pendulum dynamics:
modeling, computation, and experimentation. [Internet] [Doctoral dissertation]. University of Southern California; 2009. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/238695/rec/4275.
Council of Science Editors:
Chen CJ. Multiple degree of freedom inverted pendulum dynamics:
modeling, computation, and experimentation. [Doctoral Dissertation]. University of Southern California; 2009. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/238695/rec/4275
University of Southern California
19.
Asavatesanupap, Channarong.
Fluid dynamics of a crystallizing particle in a rotating
liquid sphere.
Degree: PhD, Mechanical Engineering, 2007, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/159667/rec/2850
► In this investigation, fluid dynamics of a spherical particle in a rotating liquid sphere is studied. Such problems arise during protein crystal growth by the…
(more)
▼ In this investigation, fluid dynamics of a spherical
particle in a rotating liquid sphere is studied. Such problems
arise during protein crystal growth by the containerless approach
in which a drop of protein solution is levitated against gravity,
and rotated steadily by a torque from an acoustic field. Viscosity
of the solution is assumed to be sufficiently high such that
viscous force dominates and the second-order effects in the
acoustic field do not penetrate the drop surface. The analysis is
carried out at very small Reynolds and Taylor numbers for which the
fluid flow is treated by Stokes approximation. With a given
geometric configuration, the velocity field is calculated and used
to determine the particle velocity at a given time. By integrating
the particle velocity, the particle path is obtained and used for
optimizing the rotation rate of the drop in an attempt to keep the
particle fully contained in the drop.; In addition, the transient
dynamics of a rotating levitated liquid drop in unbounded gaseous
fluid is investigated. A liquid drop is considered to experience
two different fundamental transients, one when the torque is turned
off and another when the torque is turned on. The motion of the
fluids in the drop interior and surroundings is described by the
Stokes equations with the time-derivative term included. The
solutions are obtained analytically by the Laplace transform
technique. The results show that the transient effects caused by
the applied torque are relatively small for the high-viscosity
solution considered. Hence, for most applications of containerless
protein crystal growth, the liquid drop may be assumed to rotate
like a solid body while allowing the solid particle relative motion
within that framework.
Advisors/Committee Members: Sadhal, Satwindar S. (Committee Chair), Egolfopoulos, Fokion N. (Committee Member), Redekopp, Larry G. (Committee Member), Shing, Katherine S. (Committee Member).
Subjects/Keywords: rotating sphere; Stokes flow; liquid sphere; levitated liquid drop; fluid dynamics
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Asavatesanupap, C. (2007). Fluid dynamics of a crystallizing particle in a rotating
liquid sphere. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/159667/rec/2850
Chicago Manual of Style (16th Edition):
Asavatesanupap, Channarong. “Fluid dynamics of a crystallizing particle in a rotating
liquid sphere.” 2007. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/159667/rec/2850.
MLA Handbook (7th Edition):
Asavatesanupap, Channarong. “Fluid dynamics of a crystallizing particle in a rotating
liquid sphere.” 2007. Web. 22 Jan 2021.
Vancouver:
Asavatesanupap C. Fluid dynamics of a crystallizing particle in a rotating
liquid sphere. [Internet] [Doctoral dissertation]. University of Southern California; 2007. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/159667/rec/2850.
Council of Science Editors:
Asavatesanupap C. Fluid dynamics of a crystallizing particle in a rotating
liquid sphere. [Doctoral Dissertation]. University of Southern California; 2007. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/159667/rec/2850
University of Southern California
20.
Kahveci, Nazli Eylem.
Robust adaptive control for unmanned aerial vehicles.
Degree: PhD, Electrical Engineering, 2007, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/487151/rec/5616
► The objective of meeting higher endurance requirements remains a challenging task for any type and size of Unmanned Aerial Vehicles (UAVs). According to recent research…
(more)
▼ The objective of meeting higher endurance requirements
remains a challenging task for any type and size of Unmanned Aerial
Vehicles (UAVs). According to recent research studies significant
energy savings can be realized through utilization of thermal
currents. The navigation strategies followed across thermal
regions, however, are based on rather intuitive assessments of
remote pilots and lack any systematic path planning approaches.
Various methods to enhance the autonomy of UAVs in soaring
applications are investigated while seeking guarantees for flight
performance improvements.; The dynamics of the aircraft, small UAVs
in particular, are affected by the environmental conditions,
whereas unmodeled dynamics possibly become significant during
aggressive flight maneuvers. Besides, the demanded control inputs
might have a magnitude range beyond the limits dictated by the
control surface actuators. The consequences of ignoring these
issues can be catastrophic. Supporting this claim NASA Dryden
Flight Research Center reports considerable performance degradation
and even loss of stability in autonomous soaring flight tests with
the subsequent risk of an aircraft crash. The existing control
schemes are concluded to suffer from limited performance.;
Considering the aircraft dynamics and the thermal characteristics
we define a vehiclespecific trajectory optimization problem to
achieve increased cross-country speed and extended range of flight.
In an environment with geographically dispersed set of thermals of
possibly limited lifespan, we identify the similarities to the
Vehicle Routing Problem (VRP) and provide both exact and
approximate guidance algorithms for the navigation of automated
UAVs. An additional stochastic approach is used to quantify the
performance losses due to incorrect thermal data while dealing with
random gust disturbances and onboard sensor measurement
inaccuracies.; One of the main contributions of this research is a
novel adaptive control design with anti-windup compensation. Our
analysis on the indirect adaptive scheme reveals that the
perturbation terms due to parameter errors do not cause any
unbounded signals in the closed-loop. The stability of the adaptive
system is established, and the properties of the proposed control
scheme are demonstrated through simulations on a UAV model with
input magnitude saturation constraints. The robust adaptive control
design is further developed to extend our results to rate-saturated
systems.
Advisors/Committee Members: Ioannou, Petros A. (Committee Chair), Safonov, Michael G. (Committee Member), Jonckheere, Edmond A. (Committee Member), Redekopp, Larry G. (Committee Member).
Subjects/Keywords: robust adaptive control; unmanned aerial vehicles; constrained control; actuator saturation; vehicle routing problem; flight trajectory optimization
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kahveci, N. E. (2007). Robust adaptive control for unmanned aerial vehicles. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/487151/rec/5616
Chicago Manual of Style (16th Edition):
Kahveci, Nazli Eylem. “Robust adaptive control for unmanned aerial vehicles.” 2007. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/487151/rec/5616.
MLA Handbook (7th Edition):
Kahveci, Nazli Eylem. “Robust adaptive control for unmanned aerial vehicles.” 2007. Web. 22 Jan 2021.
Vancouver:
Kahveci NE. Robust adaptive control for unmanned aerial vehicles. [Internet] [Doctoral dissertation]. University of Southern California; 2007. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/487151/rec/5616.
Council of Science Editors:
Kahveci NE. Robust adaptive control for unmanned aerial vehicles. [Doctoral Dissertation]. University of Southern California; 2007. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/487151/rec/5616
University of Southern California
21.
Radovich, Charles Anthony.
Experiments on spray from a rolling tire.
Degree: PhD, Aerospace & Mechanical Engineering (Computational
Fluid & Solid Mechanics), 2010, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/383304/rec/2639
► A novel laboratory apparatus has been built to understand the key mechanisms behind spray emerging from a rolling tire. Several researchers have assessed the performance…
(more)
▼ A novel laboratory apparatus has been built to
understand the key mechanisms behind spray emerging from a rolling
tire. Several researchers have assessed the performance of spray
suppression devices; however, there are no known efforts that
address the question "what needs to be suppressed?" This
investigation into how water in a tire groove evolves into a
droplet field will ultimately contribute to driver safety.; Using
high-speed imaging, water passing through a single circumferential
groove was observed to leave the tire patch in the form of a thin
liquid sheet, connecting the roadway and the tire. The sheet
disintegrates into a droplet field and the breakup modes associated
with this decay were identified with respect to Weber number.;
Weber numbers based on the properties of water, tire speed and tire
groove width were tested at 2700, 10900 and 24400. Measurements for
the breakup length of the liquid sheet showed a dependence on Weber
number proportional to We^(-1/6). The lateral displacement of the
water exiting the tire patch was also measured. These tests showed
the overall size of the spray field grows with We; however, the
maximum water volume for all We's was delivered to the same
distance from the road.; Downstream from the tire patch, a
determination of the droplet field was performed. From this study,
the distribution of droplet sizes was determined as a function of
Weber number. At We=2,700, droplet sizes between 80 and 9000
micrometers were detected, with a mean diameter near 800
micrometers. Both the range of droplet sizes and the mean diameter
were found to decrease with Weber number by approximately
We^(-1/2). Based on these size distributions, Correlation Image
Velocimetry (CIV) was used to estimate the distribution of droplet
velocities as function of their size. These results reveal a strong
correlation between droplet diameter and velocity which is
comparable to that predicted for a simple sphere.
Advisors/Committee Members: Browand, Fredrick K. (Committee Chair), Blackwelder, Ron (Committee Member), Redekopp, Larry G. (Committee Member), Shung, Kirk (Committee Member).
Subjects/Keywords: correlation image velocimetry; droplet field; droplet imaging; droplet size distribution; droplets; tire spray
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Radovich, C. A. (2010). Experiments on spray from a rolling tire. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/383304/rec/2639
Chicago Manual of Style (16th Edition):
Radovich, Charles Anthony. “Experiments on spray from a rolling tire.” 2010. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/383304/rec/2639.
MLA Handbook (7th Edition):
Radovich, Charles Anthony. “Experiments on spray from a rolling tire.” 2010. Web. 22 Jan 2021.
Vancouver:
Radovich CA. Experiments on spray from a rolling tire. [Internet] [Doctoral dissertation]. University of Southern California; 2010. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/383304/rec/2639.
Council of Science Editors:
Radovich CA. Experiments on spray from a rolling tire. [Doctoral Dissertation]. University of Southern California; 2010. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/383304/rec/2639
University of Southern California
22.
Sakai, Takahiro.
Generation and degeneration of long internal waves in
lakes.
Degree: PhD, Aerospace Engineering, 2008, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/132533/rec/2988
► The nonlinear evolution, generation and degeneration of wind-driven, basin-scale internal waves in lakes are investigated employing weakly-nonlinear, weakly-dispersive evolution models. The models studied are based…
(more)
▼ The nonlinear evolution, generation and degeneration
of wind-driven, basin-scale internal waves in lakes are
investigated employing weakly-nonlinear, weakly-dispersive
evolution models. The models studied are based on rational,
asymptotic approximations of the hydrodynamic equations of motion,
and include a two-layer model, a multi-modal model, and a
large-lake model with the effect of earth's rotation. It is found
that nonlinearity, in conjunction with the dispersive nature of the
fluid medium, plays a principle role in (i) the early stage of
degeneration of basin-scale waves through nonlinear steepening and
subsequent generation of oscillatory waves; and (ii) the transfer
of energy among multiple vertical modes in the internal field.
Strong dependence of these nonlinear processes on the background
stratification, the lake geometry, the horizontal extent of a lake,
and the spatio-temporal wind stress function are demonstrated and
quantified through a series of numerical simulations of the
different models.
Advisors/Committee Members: Redekopp, Larry G. (Committee Chair), Domaradzki, Julian A. (Committee Member), Maxworthy, Tony (Committee Member), Ziane, Mohammed (Committee Member), Hammond, Douglas E. (Committee Member).
Subjects/Keywords: internal waves; lake hydrodynamics; weakly nonlinear model; non-hydrostatic model; nonlinear waves; Kelvin wave; Poincare wave; earth rotation; multi-modal model; two-layer model; numerical simulation
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Sakai, T. (2008). Generation and degeneration of long internal waves in
lakes. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/132533/rec/2988
Chicago Manual of Style (16th Edition):
Sakai, Takahiro. “Generation and degeneration of long internal waves in
lakes.” 2008. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/132533/rec/2988.
MLA Handbook (7th Edition):
Sakai, Takahiro. “Generation and degeneration of long internal waves in
lakes.” 2008. Web. 22 Jan 2021.
Vancouver:
Sakai T. Generation and degeneration of long internal waves in
lakes. [Internet] [Doctoral dissertation]. University of Southern California; 2008. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/132533/rec/2988.
Council of Science Editors:
Sakai T. Generation and degeneration of long internal waves in
lakes. [Doctoral Dissertation]. University of Southern California; 2008. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/132533/rec/2988
University of Southern California
23.
McArthur, John.
Aerodynamics of wings at low Reynolds numbers: boundary
layer separation and reattachment.
Degree: PhD, Aerospace Engineering, 2008, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/132036/rec/564
► Due to advances in electronics technology, it is now possible to build small scale flying and swimming vehicles. These vehicles will have size and velocity…
(more)
▼ Due to advances in electronics technology, it is now
possible to build small scale flying and swimming vehicles. These
vehicles will have size and velocity scales similar to small birds
and fish, and their characteristic Reynolds number will be between
104 and 10
5. Currently, these flying and swimming vehicles do not
perform well, and very little research has been done to
characterize them, or to explain why they perform so poorly. This
dissertation documents three basic investigations into the
performance of small scale lifting surfaces, with Reynolds numbers
near 10
4.; Part I. Low Reynolds number aerodynamics. Three airfoil
shapes were studied at Reynolds numbers of 1 and 2 x 10
4: a flat
plate airfoil, a circular arc cambered airfoil, and the Eppler 387
airfoil. Lift and drag force measurements were made on both 2D and
3D conditions, with the 3D wings having an aspect ratio of 6, and
the 2D condition being approximated by placing end plates at the
wing tips.; Comparisons to the limited number of previous
measurements show adequate agreement. Previous studies have been
inconclusive on whether lifting line theory can be applied to this
range of Re, but this study shows that lifting line theory can be
applied when there are no sudden changes in the slope of the force
curves. This is highly dependent on the airfoil shape of the wing,
and explains why previous studies have been inconclusive.; Part II.
The laminar separation bubble. The Eppler 387 airfoil was studied
at two higher Reynolds numbers: 3 and 6 x 10
4. Previous studies at
a Reynolds number of 6 x 10
4 had shown this airfoil experiences a
drag increase at moderate lift, and a subsequent drag decrease at
high lift. Previous studies suggested that the drag increase is
caused by a laminar separation bubble, but the experiments used to
show this were conducted at higher Reynolds numbers and
extrapolated down.; Force measurements were combined with flow
field measurements at Reynolds numbers 3 and 6 x 10
4 to determine
whether the drag increase is really caused by the formation of a
laminar separation bubble. The results clearly indicate that the
reverse is true, and that the subsequent drag decrease is caused by
the laminar separation bubble.; Part III. The leading edge vortex.
Four wings with different sweep angles were studied at Reynolds
number 5 x 10
4: sweep angles of 0deg, 20deg, 40deg, and 60deg. The
wings had a simple cambered plate airfoil similar to the cambered
airfoil of part I above. Each wing was built to have the same
aspect ratio, wing area, and streamwise airfoil shape. Previous
studies on bird wings speculate that simply sweeping the wings can
cause a leading edge vortex to form, which could cause substantial
improvements in performance. However, these studies were not well
controlled, and were conducted from a biological perspective.;
Qualitative and quantitative flow field measurements were combined
with force measurements to conduct a well controlled engineering
experiment on the formation and effect of a leading edge vortex on
simple swept…
Advisors/Committee Members: Spedding, Geoffrey (Committee Chair), Browand, Frederick (Committee Member), Redekopp, Larry G. (Committee Member), Blackwelder, Ron (Committee Member), Bickers, Nelson Eugene, Jr. (Committee Member).
Subjects/Keywords: wing; airfoil; laminar; transition; low Reynolds number; separation; boundary layer; reattachment
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APA (6th Edition):
McArthur, J. (2008). Aerodynamics of wings at low Reynolds numbers: boundary
layer separation and reattachment. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/132036/rec/564
Chicago Manual of Style (16th Edition):
McArthur, John. “Aerodynamics of wings at low Reynolds numbers: boundary
layer separation and reattachment.” 2008. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/132036/rec/564.
MLA Handbook (7th Edition):
McArthur, John. “Aerodynamics of wings at low Reynolds numbers: boundary
layer separation and reattachment.” 2008. Web. 22 Jan 2021.
Vancouver:
McArthur J. Aerodynamics of wings at low Reynolds numbers: boundary
layer separation and reattachment. [Internet] [Doctoral dissertation]. University of Southern California; 2008. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/132036/rec/564.
Council of Science Editors:
McArthur J. Aerodynamics of wings at low Reynolds numbers: boundary
layer separation and reattachment. [Doctoral Dissertation]. University of Southern California; 2008. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/132036/rec/564
University of Southern California
24.
Cetinić, Ivona.
Harmful algal blooms in the urbanized coastal ocean: an
application of remote sensing for understanding, characterization
and prediction.
Degree: PhD, Biology, 2009, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/177691/rec/3127
► Harmful Algal Blooms (HABs) in Southern California have become recurring events with impacts that surpass the realm of ocean ecosystems. Phytoplankton blooms are natural phenomena,…
(more)
▼ Harmful Algal Blooms (HABs) in
Southern California
have become recurring events with impacts that surpass the realm of
ocean ecosystems. Phytoplankton blooms are natural phenomena, and
the same environmental forcings that drive changes in primary
productivity and nutrient cycling in the coastal ocean will promote
HABs too, including human influences. Therefore, to predict the
initiation of HABs, one must define the specific environmental,
chemical, and physical parameters that allow the success of the
specific species. Recently developed tools and techniques for
realtime coastal observing systems allow us to observe dynamics of
the coastal ocean on the appropriate spatial and temporal scales,
to explore the dynamics of the coastal ocean, to monitor the
nutrient loadings, and to follow the development of the HABs. Field
studies conducted during 2005 confirmed that observed the
transition from the diatom dominated spring to the dinoflagellate
dominated summer, both in surface and subsurface waters, was
dependent on natural processes affecting the coastal ocean.
Lingulodinium polyedrum, our model organism, was present with bloom
abundances (~10
5 cells L
-1) found during the summer, concurrent
with low temperature episodes nearshore. Historical temperature
record analysis supports our findings on the occurrence of cool
temperature anomalies during L. polyedrum blooms in the
Southern
California Bight, and infer primary controls of temperature,mixed
layer depth, and nutrient availability for bloom formation.; Using
optical instruments deployed on Slocum gliders, we managed to
follow the outfall plume, to differentiate it from the natural
occurring water masses in the coastal ocean, and to calculate
suspended particulate material concentration within the plume. No
interaction was found between the nutrient rich plume water and the
phytoplankton community. Optical tools were further used in
development of red tide spectral indices based on L. polyedrum
inherent optical properties. These indices proved to be a
successful tool for detection of L. polyedrum blooms in this area,
both for in situ absorption and for mooring collected hyperspectral
remote sensing reflectance datasets.
Advisors/Committee Members: Jones, Burton H.Caron, David A. (Committee Chair), Fuhrman, Jed Alan (Committee Member), Capone, Douglas G. (Committee Member), Kiefer, Dale A. (Committee Member), Redekopp, Larry G. (Committee Member).
Subjects/Keywords: harmful algal blooms; optics; remote sensing; red tides; autonomous underwater vehicles; gliders; plume; Lingulodinium polyedrum; phytoplankton
Record Details
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Cetinić, I. (2009). Harmful algal blooms in the urbanized coastal ocean: an
application of remote sensing for understanding, characterization
and prediction. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/177691/rec/3127
Chicago Manual of Style (16th Edition):
Cetinić, Ivona. “Harmful algal blooms in the urbanized coastal ocean: an
application of remote sensing for understanding, characterization
and prediction.” 2009. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/177691/rec/3127.
MLA Handbook (7th Edition):
Cetinić, Ivona. “Harmful algal blooms in the urbanized coastal ocean: an
application of remote sensing for understanding, characterization
and prediction.” 2009. Web. 22 Jan 2021.
Vancouver:
Cetinić I. Harmful algal blooms in the urbanized coastal ocean: an
application of remote sensing for understanding, characterization
and prediction. [Internet] [Doctoral dissertation]. University of Southern California; 2009. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/177691/rec/3127.
Council of Science Editors:
Cetinić I. Harmful algal blooms in the urbanized coastal ocean: an
application of remote sensing for understanding, characterization
and prediction. [Doctoral Dissertation]. University of Southern California; 2009. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/177691/rec/3127
University of Southern California
25.
Lilly, Taylor C.
Laser manipulation of atomic and molecular flows.
Degree: PhD, Aerospace Engineering, 2010, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/352839/rec/3746
► The continuing advance of laser technology enables a range of broadly applicable, laser-based flow manipulation techniques. The characteristics of these laser-based flow manipulations suggest that…
(more)
▼ The continuing advance of laser technology enables a
range of broadly applicable, laser-based flow manipulation
techniques. The characteristics of these laser-based flow
manipulations suggest that they may augment, or be superior to,
such traditional electro-mechanical methods as ionic flow control,
shock tubes, and small scale wind tunnels. In this study,
methodology was developed for investigating laser flow manipulation
techniques, and testing their feasibility for a number of
aerospace, basic physics, and micro technology applications.
Theories for laser-atom and laser-molecule interactions have been
under development since the advent of laser technology. The
theories have yet to be adequately integrated into kinetic flow
solvers. Realizing this integration would greatly enhance the
scaling of laser-species interactions beyond the realm of
ultra-cold atomic physics. This goal was realized in the present
study. A representative numerical investigation, of laser-based
neutral atomic and molecular flow manipulations, was conducted
using near-resonant and non-resonant laser fields. To simulate the
laser interactions over a range of laser and flow conditions, the
following tools were employed: a custom collisionless gas particle
trajectory code and a specifically modified version of the Direct
Simulation Monte Carlo statistical kinetic solver known as SMILE.
In addition to the numerical investigations, a validating
experiment was conducted. The experimental results showed good
agreement with the numerical simulations when experimental
parameters, such as finite laser line width, were taken into
account. Several areas of interest were addressed: laser induced
neutral flow steering, collimation, direct flow acceleration, and
neutral gas heating. Near-resonant continuous wave laser, and
non-resonant pulsed laser, interactions with cesium and nitrogen
were simulated.; These simulations showed trends and some
limitations associated with these interactions, used for flow
steering and collimation. The use of one of these interactions, the
induced dipole force, was extended beyond a single Gaussian laser
field. The interference patterns associated with
counter-propagating laser fields, or “optical lattices,” were shown
to be capable of both direct species acceleration and gas heating.
This study resulted in predictions for a continuous, resonant
laser-cesium flow with accelerations of 106 m/s2. For this
circumstance, a future straightforward proof of principle
experiment has been identified. To demonstrate non-resonant gas
heating, a series of pulsed optical lattices were simulated
interacting with neutral non-polar species. An optimum time between
pulses was identified as a function of the collisional relaxation
time. Using the optimum time between pulses, molecular nitrogen
simulations showed an increase in gas temperature from 300 K to
2470 K at 1 atm, for 50 successive optical lattice pulses. A second
proof of principle experiment was identified for future
investigation.
Advisors/Committee Members: Muntz, E. Phil (Committee Chair), Bickers, Nelson Eugene, Jr. (Committee Member), Ketsdever, Andrew (Committee Member), Gimelshein, Sergey (Committee Member), Redekopp, Larry G. (Committee Member).
Subjects/Keywords: molecular beams; atomic beams; laser-atom interaction; laser-molecule interaction; laser flow manipulation; numerical simulation; DSMC; Direct Simulation Monte Carlo; experiment; cesium
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APA ·
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MLA ·
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CSE |
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to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Lilly, T. C. (2010). Laser manipulation of atomic and molecular flows. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/352839/rec/3746
Chicago Manual of Style (16th Edition):
Lilly, Taylor C. “Laser manipulation of atomic and molecular flows.” 2010. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/352839/rec/3746.
MLA Handbook (7th Edition):
Lilly, Taylor C. “Laser manipulation of atomic and molecular flows.” 2010. Web. 22 Jan 2021.
Vancouver:
Lilly TC. Laser manipulation of atomic and molecular flows. [Internet] [Doctoral dissertation]. University of Southern California; 2010. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/352839/rec/3746.
Council of Science Editors:
Lilly TC. Laser manipulation of atomic and molecular flows. [Doctoral Dissertation]. University of Southern California; 2010. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/352839/rec/3746
University of Southern California
26.
King, Leslie B.
Effect of surfactants on the growth and departure of bubbles
from solid surfaces.
Degree: PhD, Mechanical Engineering, 2009, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/270253/rec/2184
► Bubbles are an important mass and energy transport mechanism and are present in many industrial systems. Boiling, fermentation, and aeration systems are a few examples…
(more)
▼ Bubbles are an important mass and energy transport
mechanism and are present in many industrial systems. Boiling,
fermentation, and aeration systems are a few examples where bubbles
are key to mass and energy transport. In particular, there is
scientific interest because of heat transfer fundamentals
associated with the boiling phenomenon in various systems.
Typically, bubbles form (nucleate) and grow on the crevices of
solid surfaces. In a gravity field, they detach due to the presence
of buoyancy. The process begins with simple growth after
nucleation, followed by vertical elongation near the attachment
point (necking phenomenon), and ending with detachment. Bubble
formation time and departure size can influence the efficiency of
these systems. It has been observed that a surfactant added to an
ebullient flow field reduces the departure size of the bubble and
the formation time. Although the surfactants being used cause a
reduction in surface tension, the effect on departure size is
opposite to that of a pure fluid with lower surface tension. To
understand the reduction in bubble size, the flow field around the
bubble together with surfactant transport is being studied. Bubble
growth and departure models have been developed using computational
fluid dynamics (CFD) with the Fluent package. Experiments have been
conducted to capture the growth of the bubble with and without
surfactants in deionized water using injected air to create a
bubble in an isothermal system (instead of vapor bubbles as in
boiling). This choice is made so as to isolate the effect of
surfactant additives from thermal effects. Particle image
velocimetry (PIV) test were also carried out to quantify the flow
around a forming bubble. The results indicate that necking occurs
more rapidly with a surfactant present. A surface tension gradient
creates a tangential stress at the surface and causes it to move in
the direction of the higher surface tension.; This movement causes
the fluid in the neighborhood of the interface to move. This is
called Marangoni convection. The fluid motion, in the bulk,
therefore has both radial and tangential components. Final
calculations have shown that the tangential velocity causes an
increase in total pressure on the neck of the bubble. The
additional force causes the neck to collapse more
rapidly.
Advisors/Committee Members: Sadhal, Satwindar S. (Committee Chair), Redekopp, Larry G. (Committee Member), Egolfopoulos, Fokion N. (Committee Member), Yang, Bingen (Committee Member), Shing, Katherine S. (Committee Member).
Subjects/Keywords: bubbles; surfactant; surface tension gradient; mass transport; hydrodynamic forces
Record Details
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
King, L. B. (2009). Effect of surfactants on the growth and departure of bubbles
from solid surfaces. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/270253/rec/2184
Chicago Manual of Style (16th Edition):
King, Leslie B. “Effect of surfactants on the growth and departure of bubbles
from solid surfaces.” 2009. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/270253/rec/2184.
MLA Handbook (7th Edition):
King, Leslie B. “Effect of surfactants on the growth and departure of bubbles
from solid surfaces.” 2009. Web. 22 Jan 2021.
Vancouver:
King LB. Effect of surfactants on the growth and departure of bubbles
from solid surfaces. [Internet] [Doctoral dissertation]. University of Southern California; 2009. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/270253/rec/2184.
Council of Science Editors:
King LB. Effect of surfactants on the growth and departure of bubbles
from solid surfaces. [Doctoral Dissertation]. University of Southern California; 2009. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/270253/rec/2184
. 
Open Access Theses and Dissertations