subject:( Active Drag)

University of Sydney

1. Hazrati, Pendar. Active drag of front crawl swimmers: estimation, measurement and analysis .

Degree: 2016, University of Sydney

► Researchers’ methods of estimating water’s resistance (drag) to a swimmer include the Assisted Towing Method (ATM) with fluctuating speed. This thesis aimed to assess the… (more)

Subjects/Keywords: Active Drag; Measurement; Analysis; Swimming

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APA (6^th Edition):

Hazrati, P. (2016). Active drag of front crawl swimmers: estimation, measurement and analysis . (Thesis). University of Sydney. Retrieved from http://hdl.handle.net/2123/15774

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Hazrati, Pendar. “Active drag of front crawl swimmers: estimation, measurement and analysis .” 2016. Thesis, University of Sydney. Accessed April 16, 2021. http://hdl.handle.net/2123/15774.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Hazrati, Pendar. “Active drag of front crawl swimmers: estimation, measurement and analysis .” 2016. Web. 16 Apr 2021.

Vancouver:

Hazrati P. Active drag of front crawl swimmers: estimation, measurement and analysis . [Internet] [Thesis]. University of Sydney; 2016. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/2123/15774.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Hazrati P. Active drag of front crawl swimmers: estimation, measurement and analysis . [Thesis]. University of Sydney; 2016. Available from: http://hdl.handle.net/2123/15774

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Loughborough University

2. Littlewood, Rob. Novel methods of drag reduction for squareback road vehicles.

Degree: PhD, 2013, Loughborough University

URL: http://hdl.handle.net/2134/12534

► Road vehicles are still largely a consumer product and as such the styling of a vehicle becomes a significant factor in how commercially successful a… (more)

Subjects/Keywords: 629.3; Aero; Aerodynamics; Drag; Car; Drag reduction; Active flow control; Synthetic jets; Steady blowing; Base bleed; Constant blowing

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APA (6^th Edition):

Littlewood, R. (2013). Novel methods of drag reduction for squareback road vehicles. (Doctoral Dissertation). Loughborough University. Retrieved from http://hdl.handle.net/2134/12534

Chicago Manual of Style (16^th Edition):

Littlewood, Rob. “Novel methods of drag reduction for squareback road vehicles.” 2013. Doctoral Dissertation, Loughborough University. Accessed April 16, 2021. http://hdl.handle.net/2134/12534.

MLA Handbook (7^th Edition):

Littlewood, Rob. “Novel methods of drag reduction for squareback road vehicles.” 2013. Web. 16 Apr 2021.

Vancouver:

Littlewood R. Novel methods of drag reduction for squareback road vehicles. [Internet] [Doctoral dissertation]. Loughborough University; 2013. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/2134/12534.

Council of Science Editors:

Littlewood R. Novel methods of drag reduction for squareback road vehicles. [Doctoral Dissertation]. Loughborough University; 2013. Available from: http://hdl.handle.net/2134/12534

Indiana University

3. White, Joshua Childs. Development and Validity Assessment of the Max Power Model for the Detection, Separation, and Quantification of Differences in Resistive and Propulsive Forces in Swimming .

Degree: 2010, Indiana University

URL: http://hdl.handle.net/2022/7706

► Purpose: The purpose of this study was twofold. First, a new method, the Max Power Model, for assessing resistive (Fres) and propulsive (Fprop) forces using… (more)

▼ Purpose: The purpose of this study was twofold. First, a new method, the Max Power Model, for assessing resistive (Fres) and propulsive (Fprop) forces using tethered swimming was developed. The Max Power Model (MPM) is based on the maximum power that a swimmer can deliver to an external load while swimming (Pmax) and its relationship with the maximum velocity of the swimmer (vmax). The development of the MPM was accomplished in three ways: examination of the shape of the Pmax vs. vmax curve, development of a method of comparing Pmax vs. vmax curves, and finally testing the sensitivity of the method to large changes using the four competitive strokes and underwater dolphin kicking. Second, the validity of the MPM was assessed by comparison with the Velocity Perturbation Model (VPM) and response to independent changes in Fres and Fprop during swimming (as supplied by a pocketed dragsuit, a wetsuit, hand paddles, fist gloves). Results: The MPM was developed effectively. The Pmax vs. vmax curve was found to be best described as an exponential function. Comparisons of Pmax vs. vmax curves were therefore made after linearization using the natural log of Pmax. If the slopes were similar, the comparisons were accomplished using ANCOVA with vmax as the covariate, otherwise a t-test for differences in slope was used. The MPM was sensitive to large changes in the swimming condition as seen through significant differences (p < 60; 0.05) in an ANCOVA for competitive stroke and a significantly different slope of ln(Pmax) vs. vmax for underwater dolphin kick in comparison with the competitive strokes. Assessment of the validity of the MPM yielded mixed results. The MPM showed a strong relationship to the VPM. However, the VPM showed no significant differences between any of the equipment treatment conditions in either the calculated Fres or the drag coefficient indicating an inability to detect small changes in Fres and Fprop. The MPM showed more promise, responding as expected to a majority of the equipment conditions. Conclusion: While still in need of further exploration and validation, the MPM has promise as a simple method to detect, separate, and quantify differences in Fres and Fprop during swimming. Advisors/Committee Members: Stager, Joel M (advisor).

Subjects/Keywords: Sprint Swimming; Tethered Swimming; Active Drag; Swimming Propulsion

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APA (6^th Edition):

White, J. C. (2010). Development and Validity Assessment of the Max Power Model for the Detection, Separation, and Quantification of Differences in Resistive and Propulsive Forces in Swimming . (Thesis). Indiana University. Retrieved from http://hdl.handle.net/2022/7706

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

White, Joshua Childs. “Development and Validity Assessment of the Max Power Model for the Detection, Separation, and Quantification of Differences in Resistive and Propulsive Forces in Swimming .” 2010. Thesis, Indiana University. Accessed April 16, 2021. http://hdl.handle.net/2022/7706.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

White, Joshua Childs. “Development and Validity Assessment of the Max Power Model for the Detection, Separation, and Quantification of Differences in Resistive and Propulsive Forces in Swimming .” 2010. Web. 16 Apr 2021.

Vancouver:

White JC. Development and Validity Assessment of the Max Power Model for the Detection, Separation, and Quantification of Differences in Resistive and Propulsive Forces in Swimming . [Internet] [Thesis]. Indiana University; 2010. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/2022/7706.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

White JC. Development and Validity Assessment of the Max Power Model for the Detection, Separation, and Quantification of Differences in Resistive and Propulsive Forces in Swimming . [Thesis]. Indiana University; 2010. Available from: http://hdl.handle.net/2022/7706

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Tennessee – Knoxville

4. Clark, Emily Buckman. Analysis and Optimization of Unsteady Flow Past a Circular Cylinder Using a Harmonic Balance Method.

Degree: MS, Aerospace Engineering, 2013, University of Tennessee – Knoxville

URL: https://trace.tennessee.edu/utk_gradthes/2402

► Two-dimensional laminar flow over a circular cylinder was investigated in this work. Three cases were considered in which the cylinder was either stationary, in… (more)

Subjects/Keywords: vortex suppression; lift; drag; finite difference; active control; sensitivity; Aerodynamics and Fluid Mechanics; Aerospace Engineering; Engineering

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APA (6^th Edition):

Clark, E. B. (2013). Analysis and Optimization of Unsteady Flow Past a Circular Cylinder Using a Harmonic Balance Method. (Thesis). University of Tennessee – Knoxville. Retrieved from https://trace.tennessee.edu/utk_gradthes/2402

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Clark, Emily Buckman. “Analysis and Optimization of Unsteady Flow Past a Circular Cylinder Using a Harmonic Balance Method.” 2013. Thesis, University of Tennessee – Knoxville. Accessed April 16, 2021. https://trace.tennessee.edu/utk_gradthes/2402.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Clark, Emily Buckman. “Analysis and Optimization of Unsteady Flow Past a Circular Cylinder Using a Harmonic Balance Method.” 2013. Web. 16 Apr 2021.

Vancouver:

Clark EB. Analysis and Optimization of Unsteady Flow Past a Circular Cylinder Using a Harmonic Balance Method. [Internet] [Thesis]. University of Tennessee – Knoxville; 2013. [cited 2021 Apr 16]. Available from: https://trace.tennessee.edu/utk_gradthes/2402.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Clark EB. Analysis and Optimization of Unsteady Flow Past a Circular Cylinder Using a Harmonic Balance Method. [Thesis]. University of Tennessee – Knoxville; 2013. Available from: https://trace.tennessee.edu/utk_gradthes/2402

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Michigan

5. Castro-Feliciano, Esteban L. Co-Design of Planing Craft and Active Control Systems.

Degree: PhD, Naval Architecture and Marine Engineering, 2016, University of Michigan

URL: http://hdl.handle.net/2027.42/133234

► The available planing craft design tools and guidelines were not envisioned to be used with vessels that have Active Control Systems (ACS). Consequently, vessels with… (more)

▼ The available planing craft design tools and guidelines were not envisioned to be used with vessels that have Active Control Systems (ACS). Consequently, vessels with ACS are conventionally designed in a sequential manner: first, the geometry of the vessel is designed using traditional guidelines, and then the ACS is implemented. However, sequential design is not always optimal for systems whose dynamics are coupled. This work establishes a co-design framework for a planing craft and its ACS, combines tools in the disciplines of naval architecture, control systems, and optimization in a novel way to perform co-design studies, and compares them with the sequential design. The study was limited to numerical studies based on reduced order models and the strip-theory time-domain planing craft simulation program POWERSEA. The planing crafts studied are prismatic and have a 12 m length and 10.2 tonne displacement. The ACS is modeled as body forces and the controller investigated is a linear-quadratic regulator (LQR); this work did not look into the design or optimization of the ACS's hardware. The calm-water performance was measured with a semi-empirical reduced order model and with POWERSEA. The seakeeping and seaway drag were estimated in sea states (SS) 2 and 3 and the Pareto front was estimated from an exhaustive search that varied the vessel's longitudinal center of gravity (lcg), deadrise and pitch velocity gain for the LQR estimation. Afterwards the Pareto estimation technique Adaptive Weighted Sum (AWS) was modified to better suit the Pareto estimation performed in this study, resulting in the Modified Adaptive Weighted Sum (MAWS). MAWS was applied to the case where the vessel's beam, lcg, deadrise and the LQR's pitch and heave velocity gains are optimized for SS 3. Finally, the real-world feasibility of designing the sequential and co-design vessels, obtained from the MAWS, was investigated with a case-study. Co-designing shows potential to significantly reduce calm-water and seaway drag (10% in some cases), and improve seakeeping (20% in some cases). Thus, the co-design framework offers an opportunity for designing planing craft that are more efficient and have better seakeeping than any planing craft ever built before. Advisors/Committee Members: Sun, Jing (committee member), Troesch, Armin W (committee member), Revzen, Shai (committee member), Singer, David Jacob (committee member).

Subjects/Keywords: design of planing craft with active control systems; improving seakeeping and drag of high speed vessels with active control systems; Naval Architecture and Marine Engineering; Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Castro-Feliciano, E. L. (2016). Co-Design of Planing Craft and Active Control Systems. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/133234

Chicago Manual of Style (16^th Edition):

Castro-Feliciano, Esteban L. “Co-Design of Planing Craft and Active Control Systems.” 2016. Doctoral Dissertation, University of Michigan. Accessed April 16, 2021. http://hdl.handle.net/2027.42/133234.

MLA Handbook (7^th Edition):

Castro-Feliciano, Esteban L. “Co-Design of Planing Craft and Active Control Systems.” 2016. Web. 16 Apr 2021.

Vancouver:

Castro-Feliciano EL. Co-Design of Planing Craft and Active Control Systems. [Internet] [Doctoral dissertation]. University of Michigan; 2016. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/2027.42/133234.

Council of Science Editors:

Castro-Feliciano EL. Co-Design of Planing Craft and Active Control Systems. [Doctoral Dissertation]. University of Michigan; 2016. Available from: http://hdl.handle.net/2027.42/133234

University of Melbourne

6. Abbassi, Reza. Drag reduction via manipulation of large-scale coherent structures in a high Reynolds-number turbulent boundary layer.

Degree: 2018, University of Melbourne

URL: http://hdl.handle.net/11343/213934

► The large-scale coherent structures in the outer region of a high-Reynolds-number turbulent boundary layer (TBL) have been shown to be highly energetic with an influence… (more)

▼ The large-scale coherent structures in the outer region of a high-Reynolds-number turbulent boundary layer (TBL) have been shown to be highly energetic with an influence that extends down to the wall and thus directly affects the skin friction. This thesis is concerned with a drag reduction strategy that involves targeting these large-scale motions. The notion of high-Reynolds-number TBL refers to the case where an outer site in the spectrogram of the streamwise velocity fluctuations emerges, which is a manifestation of the energy of the large-scale structures. The largest length of the manipulated large-scale motions in this study measures 10δ in the streamwise direction (where δ is the boundary layer thickness). The characteristic Reynolds number of a TBL is considered to be high, as an outer site in the spectrogram of the streamwise velocity fluctuations emerges. The current experimental study investigates a feedforward control scheme in which the large-scale motions and very large-scale motions of a zero-pressure-gradient TBL at an approximate friction Reynolds number of 14400 were manipulated selectively. An array of nine wall-shear stress sensors—0.07δ apart in the spanwise direction—was utilized to measure the wall-shear stress fluctuations. The wall signature of the large-scale structures was resolved in real-time from the fluctuating signal of each individual wall-shear stress sensor. At 1.6δ downstream of the sensing point, an array of nine rectangular wall-normal jets was designated, each aligned in the streamwise direction with a corresponding wall-shear stress sensor, forming nine sensor-actuator pairs. On/off wall-normal jet airflows through the rectangular planes provided the actuation, and the penetration height reached the upper-bound of the log-region. Large-scale structures possess bilateral characteristics; their instantaneous streamwise velocity are either higher or lower than the mean streamwise velocity at each wall-normal height. These high- and low-speed regions are accompanied by respective down- and up-ward wall-normal velocity components. In a conditional sense, this results in a manifestation of counter-rotating roll modes in the spanwise–wall-normal plane. Therefore, the wall-normal jet actuators were programmed to be synchronized with either the high- or low-speed regions. As the wall-normal jet actuation was synchronized with the high-speed events, it was implicitly synchronized with the down-wash sections of the counter-rotating roll modes. This led to an opposition mechanism of the control scheme (opposing control scheme), and the intensity of the high- and low-speed events was reduced. A maximum reduction of 3.2% in the mean wall-shear stress was measured at 1.6δ downstream of the actuators. The opposite occurred when the wall-normal jet actuation was synchronized with the low-speed events. For this type of manipulation, the actuation was implicitly synchronized with the up-wash sections of the counter-rotating roll modes. This led to a reinforcing control mechanism…

Subjects/Keywords: turbulent boundary layer; coherent structures; active flow control; drag reduction; high Reynolds number; large-scale motions; feedforward control scheme; opposition control scheme; selective wall-normal jet actuation; skin friction drag; wall-shear stress; large-scale control scheme; premultiplied energy spectrogram

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Abbassi, R. (2018). Drag reduction via manipulation of large-scale coherent structures in a high Reynolds-number turbulent boundary layer. (Doctoral Dissertation). University of Melbourne. Retrieved from http://hdl.handle.net/11343/213934

Chicago Manual of Style (16^th Edition):

Abbassi, Reza. “Drag reduction via manipulation of large-scale coherent structures in a high Reynolds-number turbulent boundary layer.” 2018. Doctoral Dissertation, University of Melbourne. Accessed April 16, 2021. http://hdl.handle.net/11343/213934.

MLA Handbook (7^th Edition):

Abbassi, Reza. “Drag reduction via manipulation of large-scale coherent structures in a high Reynolds-number turbulent boundary layer.” 2018. Web. 16 Apr 2021.

Vancouver:

Abbassi R. Drag reduction via manipulation of large-scale coherent structures in a high Reynolds-number turbulent boundary layer. [Internet] [Doctoral dissertation]. University of Melbourne; 2018. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/11343/213934.

Council of Science Editors:

Abbassi R. Drag reduction via manipulation of large-scale coherent structures in a high Reynolds-number turbulent boundary layer. [Doctoral Dissertation]. University of Melbourne; 2018. Available from: http://hdl.handle.net/11343/213934

University of Michigan

7. Diez-Garias, Francisco J. Electrokinetic microactuator arrays for active sublayer control of turbulent boundary layers.

Degree: PhD, Mechanical engineering, 2002, University of Michigan

URL: http://hdl.handle.net/2027.42/129377

► The present study has been the first to examine the electrokinetic principle as the basis for a new class of microscale actuator arrays for active… (more)

▼ The present study has been the first to examine the electrokinetic principle as the basis for a new class of microscale actuator arrays for active sublayer control on full scale aeronautical and hydronautical vehicles under realistic operating conditions. The Helmholtz-Smoluchowski scalings that govern such electrokinetic actuator arrays show significant performance advantages from their miniaturization to the microscale. The electrokinetic microactuator arrays that are the subject of this study seek to interrupt the bursting process associated with naturally-occurring streamwise sublayer vortices in the turbulent boundary layer. Specific performance requirements for microactuator spacing, flow rate, and frequency response for active sublayer control have been determined from fundamental scaling laws for the streamwise vortical structures in the sublayer of turbulent boundary layers. In view of the inherently local nature of the sublayer dynamics, a general system architecture for microactuator arrays appropriate for active sublayer control has been developed based on the concept of relatively small and independent unit cells, each with their own sensing, processing, and actuation capability, that greatly simplifies the sensing and processing requirements needed to achieve practical sublayer control. A fundamental three-layer design has been developed for such electrokinetic microactuator arrays, in which electrokinetic flow is induced by an impulsively applied electric field across a center layer, with a bottom layer containing an electrolyte reservoir and a common electrode, and a top layer that containing individual electrodes and lead-outs for each microactuator in the unit cell. Microfabrication techniques have been developed that permit mass production of large numbers of individual electrokinetic microactuators in unit cells on comparatively large-area tiles. Several generations of such electrokinetic microactuator arrays have been built leading to the MEKA-5 full-scale hydronautical array, composed of 25,600 individual electrokinetic microactuators with 350 mum center-to-center spacings, arranged in a 40 x 40 pattern of unit cells, each composed of a 4 x 4 matrix of actuators. MEMS design and fabrication processes were used to produce a top layer for the MEKA-5 hydronautical-scale array. Stereo-PIV measurements successfully demonstrated lateral displacement of synthetically-generated streamwise vortical structures by volumetric pumping from a wall actuator in a set of large-scale wind tunnel tests. Advisors/Committee Members: Dahm, Werner J. A. (advisor).

Subjects/Keywords: Active; Arrays; Control; Drag; Electrokinetic; Microactuator; Sublayer; Turbulent Boundary Layers

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APA (6^th Edition):

Diez-Garias, F. J. (2002). Electrokinetic microactuator arrays for active sublayer control of turbulent boundary layers. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/129377

Chicago Manual of Style (16^th Edition):

Diez-Garias, Francisco J. “Electrokinetic microactuator arrays for active sublayer control of turbulent boundary layers.” 2002. Doctoral Dissertation, University of Michigan. Accessed April 16, 2021. http://hdl.handle.net/2027.42/129377.

MLA Handbook (7^th Edition):

Diez-Garias, Francisco J. “Electrokinetic microactuator arrays for active sublayer control of turbulent boundary layers.” 2002. Web. 16 Apr 2021.

Vancouver:

Diez-Garias FJ. Electrokinetic microactuator arrays for active sublayer control of turbulent boundary layers. [Internet] [Doctoral dissertation]. University of Michigan; 2002. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/2027.42/129377.

Council of Science Editors:

Diez-Garias FJ. Electrokinetic microactuator arrays for active sublayer control of turbulent boundary layers. [Doctoral Dissertation]. University of Michigan; 2002. Available from: http://hdl.handle.net/2027.42/129377

Brno University of Technology

8. Skarolek, Vilém. Výpočetní studie možností využití aktivního řízení proudu k snížení intenzity koncových vírů na křídle: A computational study on the effects of active flow control to the evolution of the wingtip vortices of a three dimensional wing.

Degree: 2019, Brno University of Technology

URL: http://hdl.handle.net/11012/17197

► In the present thesis, series of RANS calculations of the flow past a NACA 0015 wing at different angles of attack with active flow control… (more)

Subjects/Keywords: aktivní řízení proudu; trysky; koncový vír; vysoké Reynoldsovo číslo; vyfukování; snížení odporu; active flow control; jets; wingtip vortex; high Reynolds; blowing; drag reduction

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APA (6^th Edition):

Skarolek, V. (2019). Výpočetní studie možností využití aktivního řízení proudu k snížení intenzity koncových vírů na křídle: A computational study on the effects of active flow control to the evolution of the wingtip vortices of a three dimensional wing. (Thesis). Brno University of Technology. Retrieved from http://hdl.handle.net/11012/17197

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Skarolek, Vilém. “Výpočetní studie možností využití aktivního řízení proudu k snížení intenzity koncových vírů na křídle: A computational study on the effects of active flow control to the evolution of the wingtip vortices of a three dimensional wing.” 2019. Thesis, Brno University of Technology. Accessed April 16, 2021. http://hdl.handle.net/11012/17197.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Skarolek, Vilém. “Výpočetní studie možností využití aktivního řízení proudu k snížení intenzity koncových vírů na křídle: A computational study on the effects of active flow control to the evolution of the wingtip vortices of a three dimensional wing.” 2019. Web. 16 Apr 2021.

Vancouver:

Skarolek V. Výpočetní studie možností využití aktivního řízení proudu k snížení intenzity koncových vírů na křídle: A computational study on the effects of active flow control to the evolution of the wingtip vortices of a three dimensional wing. [Internet] [Thesis]. Brno University of Technology; 2019. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/11012/17197.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Skarolek V. Výpočetní studie možností využití aktivního řízení proudu k snížení intenzity koncových vírů na křídle: A computational study on the effects of active flow control to the evolution of the wingtip vortices of a three dimensional wing. [Thesis]. Brno University of Technology; 2019. Available from: http://hdl.handle.net/11012/17197

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Georgia Tech

9. Yeshala, Nandita. A coupled lattice Boltzmann-Navier-Stokes methodology for drag reduction.

Degree: PhD, Aerospace Engineering, 2010, Georgia Tech

URL: http://hdl.handle.net/1853/37097

► Helicopter performance is greatly influenced by its drag. Pylons, fuselage, landing gear, and especially the rotor hub of a helicopter experience large separated flow regions,… (more)

▼ Helicopter performance is greatly influenced by its drag. Pylons, fuselage, landing gear, and especially the rotor hub of a helicopter experience large separated flow regions, even under steady level flight conditions the vehicle has been designed for, contributing to the helicopter drag. Several passive and active flow control concepts have been studied for reducing helicopter drag. While passive flow control methods reduce drag, they do so at one optimized design condition. Therefore, passive drag reduction methods may not work for helicopters that operate under widely varying flight conditions. Active flow control (AFC) methods overcome this disadvantage and consequently are widely being pursued. The present investigator has studied some of these AFC methods using computational fluid dynamics (CFD) techniques and has found synthetic (or pulsed) jets as one of the more effective drag reduction devices. Two bluff bodies, representative of helicopter components, have been studied and the mechanism behind drag reduction has been analyzed. It was found that the increase in momentum due to the jet, and a resultant reduction in the separated flow region, is the main reason for drag reduction in these configurations. In comparison with steady jets, synthetic jets were found to use less power for a greater drag reduction. The flow inside these synthetic jet devices is incompressible. It is computationally inefficient to use compressible flow solvers in incompressible regions. In such regions, using Lattice Boltzmann equations (LBE) is more suitable compared to solving the incompressible Navier-Stokes equations. The length scales close to the synthetic jet devices are very small. LBE may be used to better resolve these small length scale regions. However, using LBE throughout the whole domain would be computationally expensive since the grid spacing in the LBE solver has to be of the order of the mean free path. To address this need, a coupled Lattice Boltzmann-Navier-Stokes (LB-NS) methodology has been developed. The LBE solver has been successfully validated in a standalone manner for several benchmark cases. The solver has also been shown to be of second order accuracy. This LBE solver has been subsequently coupled with an existing Navier-Stokes (NS) solver. Validation of the coupled methodology has been done for analytical problems with known closed form solution. This LB-NS methodology is further used to simulate the flow past a cylinder where synthetic jet devices have been used to reduce drag. The LBE solver is used in the cavity of the synthetic jet nozzle while the NS solver is employed in the rest of the domain. The cylinder configuration was chosen to demonstrate drag reduction on helicopter hub shape geometries. Significant drag reduction is observed when synthetic jets are used, compared to the baseline no flow control case. Advisors/Committee Members: Sankar, Lakshmi N. (Committee Chair), Jagoda, Jeff I. (Committee Member), Martin, Preston (Committee Member), Menon, Suresh (Committee Member), Ruffin, Stephen M. (Committee Member).

Subjects/Keywords: Drag; Lattice Boltzmann; Navier-Stokes; Multiscale; Active flow control; Synthetic jet; Drag (Aerodynamics); Lattice Boltzmann methods; Computational fluid dynamics; Navier-Stokes equations

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APA (6^th Edition):

Yeshala, N. (2010). A coupled lattice Boltzmann-Navier-Stokes methodology for drag reduction. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/37097

Chicago Manual of Style (16^th Edition):

Yeshala, Nandita. “A coupled lattice Boltzmann-Navier-Stokes methodology for drag reduction.” 2010. Doctoral Dissertation, Georgia Tech. Accessed April 16, 2021. http://hdl.handle.net/1853/37097.

MLA Handbook (7^th Edition):

Yeshala, Nandita. “A coupled lattice Boltzmann-Navier-Stokes methodology for drag reduction.” 2010. Web. 16 Apr 2021.

Vancouver:

Yeshala N. A coupled lattice Boltzmann-Navier-Stokes methodology for drag reduction. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/1853/37097.

Council of Science Editors:

Yeshala N. A coupled lattice Boltzmann-Navier-Stokes methodology for drag reduction. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/37097

10. [No author]. I. Assessment of Hands-on Learning and Lecture II. Stability and Drag Reduction in Steady Capillary Flow Through Hydrophobic Channels with Minimal Helical Wire Supports.

Degree: 2014, Washington State University

URL: http://hdl.handle.net/2376/5078

► The expertise differential between instructor and student provides adequate potential for flow of expertise from the former to the latter during instruction. However, the intrinsic… (more)

▼ The expertise differential between instructor and student provides adequate potential for flow of expertise from the former to the latter during instruction. However, the intrinsic and extraneous cognitive loads (resistances to learning posed by the topic and instructional design/ implementation, respectively) need to be minimized. Multimedia learning and hands-on interactive learning are believed to reduce cognitive load over straight lecture. Several instructional configurations were compared in terms of important learning outcomes. Overall, students perceived that group miniaturized equipment-mediated instruction helped them more than lecture in terms of schema formation and aspects of competence-based education like group dynamics and hands-on skills.Stability and drag reduction during steady capillary fluid flow through hydrophobic extension springs were studied numerically and experimentally. Large-bore capillary channels formed from these springs are envisioned for phase separation and liquid-gas contacting in space and for small-scale terrestrial capillary transport. A practical realization of a structure with alternating transverse slip and no-slip boundaries that can give relatively large slip fractions and a large ratio of the length of slip sections to tube radius is a cylindrical capillary channel supported by a stretched hydrophobic spring. Some aspects of the flow in such a channel can be approximated by flow in the corresponding axisymmetric array of wire rings. Flow in such a channel is modeled by the finite element method on a periodic domain obtained by matching velocity fields at the extremities of the period. Drag reduction, measured by the slip length is found to increase with increasing pitch of the period and with increasing fraction of slip boundary, and to decrease with increasing roughness of the composite wire-plus-meniscus boundary and Reynolds number above 50. Overall, the highest drag reduction is found to occur for the highest contact angle studied (178o), Reynolds number below 50 and a smooth no-shear boundary. Stability and drag reduction during flow was studied experimentally in hydrophobic 1/4-inch and 1/8-inch springs. The ranges of stable pressures in the hydrophobic channels decreased with pitch and channel diameter. Consequently, relatively large flows up to 630 mL/min and slip lengths up to 140 µm were achieved at small pitches. Advisors/Committee Members: Van Wie, Bernard J (advisor).

Subjects/Keywords: Chemical engineering; Educational evaluation; Active Learning; Cognitive Load; Drag reduction; Multimedia; Slip length; Superhydrophobic

…Barriers in Developing Nations with a Novel Hands-on Active Pedagogy and Miniaturized Industrial… …55 3. A Tale of Two Pedagogies-Comparing Lecture and Active Learning in a Fluids and Heat… …223 7. Drag reduction for flow in superhydrophobic springs… …papers is interpedagogical differences between a passive and a more active approach in terms of… …Learning Barriers in Developing Nations with a Novel Hands-on Active Pedagogy and Miniaturized…

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APA (6^th Edition):

author], [. (2014). I. Assessment of Hands-on Learning and Lecture II. Stability and Drag Reduction in Steady Capillary Flow Through Hydrophobic Channels with Minimal Helical Wire Supports. (Thesis). Washington State University. Retrieved from http://hdl.handle.net/2376/5078

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

author], [No. “I. Assessment of Hands-on Learning and Lecture II. Stability and Drag Reduction in Steady Capillary Flow Through Hydrophobic Channels with Minimal Helical Wire Supports. ” 2014. Thesis, Washington State University. Accessed April 16, 2021. http://hdl.handle.net/2376/5078.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

author], [No. “I. Assessment of Hands-on Learning and Lecture II. Stability and Drag Reduction in Steady Capillary Flow Through Hydrophobic Channels with Minimal Helical Wire Supports. ” 2014. Web. 16 Apr 2021.

Vancouver:

author] [. I. Assessment of Hands-on Learning and Lecture II. Stability and Drag Reduction in Steady Capillary Flow Through Hydrophobic Channels with Minimal Helical Wire Supports. [Internet] [Thesis]. Washington State University; 2014. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/2376/5078.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

author] [. I. Assessment of Hands-on Learning and Lecture II. Stability and Drag Reduction in Steady Capillary Flow Through Hydrophobic Channels with Minimal Helical Wire Supports. [Thesis]. Washington State University; 2014. Available from: http://hdl.handle.net/2376/5078

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Brno University of Technology

11. Sobotka, Vojtěch. Experimentální ověření konceptu aktivního řízení proudu v automobilní aplikaci: Experimental validation of active flow control concept for automotive applications.

Degree: 2020, Brno University of Technology

URL: http://hdl.handle.net/11012/189039

► This master's thesis contains complex design of active flow control system installed on Škoda Roomster passenger car following previous research done by BUT and TUB… (more)

Subjects/Keywords: aktivní řízení proudu; osobní automobil; spoiler; snižování odporu; tlaková láhev; redukční ventil; šroubení; řezání laserem; experiment; active flow control; passenger car; spoiler; drag reduction; pressure cylinder; pressure regulator; fittings; laser cutting; experiment

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APA (6^th Edition):

Sobotka, V. (2020). Experimentální ověření konceptu aktivního řízení proudu v automobilní aplikaci: Experimental validation of active flow control concept for automotive applications. (Thesis). Brno University of Technology. Retrieved from http://hdl.handle.net/11012/189039

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Sobotka, Vojtěch. “Experimentální ověření konceptu aktivního řízení proudu v automobilní aplikaci: Experimental validation of active flow control concept for automotive applications.” 2020. Thesis, Brno University of Technology. Accessed April 16, 2021. http://hdl.handle.net/11012/189039.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Sobotka, Vojtěch. “Experimentální ověření konceptu aktivního řízení proudu v automobilní aplikaci: Experimental validation of active flow control concept for automotive applications.” 2020. Web. 16 Apr 2021.

Vancouver:

Sobotka V. Experimentální ověření konceptu aktivního řízení proudu v automobilní aplikaci: Experimental validation of active flow control concept for automotive applications. [Internet] [Thesis]. Brno University of Technology; 2020. [cited 2021 Apr 16]. Available from: http://hdl.handle.net/11012/189039.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Sobotka V. Experimentální ověření konceptu aktivního řízení proudu v automobilní aplikaci: Experimental validation of active flow control concept for automotive applications. [Thesis]. Brno University of Technology; 2020. Available from: http://hdl.handle.net/11012/189039

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

12. Whiteman, Jacob T. Active Flow Control Schemes for Bluff Body Drag Reduction.

Degree: MS, Aero/Astro Engineering, 2016, The Ohio State University

URL: http://rave.ohiolink.edu/etdc/view?acc_num=osu1452184221

► Bluff body vehicle drag is dominated by pressure drag on the rear end of the body due to the effect of momentum causing the flow… (more)

▼ Bluff body vehicle drag is dominated by pressure drag on the rear end of the body due to the effect of momentum causing the flow to detach from the body contour. This flow separation results in a pressure difference between the front and back end, making up the pressure drag. A friction force is also generated at the contact of air and solid body that contributes to the total drag, however in the case of bluff body flow this value is far outweighed by the pressure drag. The rear separation region is also dominated by complex time dependent vortices, of which this pressure drag is also dependent, thereby making the overall drag at least partially dependent on the strength and frequency of this shedding phenomena as well. In this study, both a two-dimensional and three-dimensional Ahmed model are used, however only the zero-slant angle case is studied to coincide with the majority of transportation trucks and buses that are on the road today.Numerical simulation experiments on vortex shedding and corresponding drag coefficients from a two-dimensional bluff body are performed over a range of Reynolds numbers from one to four million. The simulations are performed using ANSYS Fluent, specifically the turbulence model of k-epsilon RNG (Re-normalization Group). In order to enhance the accuracy of the shedding wake vortices, an enhanced non-equilibrium wall treatment is utilized. Active control is implemented on the body via velocity boundary conditions in the form of blowing and suction jets. These controls range in velocity from half to double the free-stream inlet velocity. An overall drag coefficient reduction in excess of 75% is observed for maximum power input to the actuators. In addition, a trend of increasing Strouhal number for each successive increase in actuator power (and corresponding reduction in drag) is noted. Important physical mechanisms involving near-body wake flow are analyzed to determine optimal wake flow pattern and corresponding control schemes.Discoveries are then used to study similar controls on the three-dimensional bluff body based on those of the two-dimensional model. For the 3-D simulations the Large Eddy Simulation model is used for the calculation of flow field variables within Fluent, however an introductory RANS analysis is performed as well. Control schemes involving suction jets are investigated. Aspects of the flow pattern such as shedding and streamlines are studied in depth in an effort to determine the most efficient application of the suction controls. These schemes seek to reduce the aerodynamic drag without constraints on the basic design of the model itself. An average of 10% drag reduction is recorded. Advisors/Committee Members: Zhuang, Mei (Advisor).

Subjects/Keywords: Aerospace Engineering; Engineering; bluff body; ahmed; drag reduction; active control; LES; RANS; Fluent; ICEM

…3.3 . . . . . . . . . . . . . . . . . . and Drag . . . . . . . . . . . . 31 40 Three… …Transient drag comparison between the two different methods . . . . 24 3.6 (Upper)… …Typical periodic drag coefficient (Lower) MATLAB fast Fourier transform of drag… …Graphical depiction of drag coefficient data from Table 3.1 . . . . . . 33 3.7 3.8 3.9 ix… …depiction of drag coefficient data from Table 3.2 . . . . . . 35 3.15 Graphical depiction of…

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APA (6^th Edition):

Whiteman, J. T. (2016). Active Flow Control Schemes for Bluff Body Drag Reduction. (Masters Thesis). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1452184221

Chicago Manual of Style (16^th Edition):

Whiteman, Jacob T. “Active Flow Control Schemes for Bluff Body Drag Reduction.” 2016. Masters Thesis, The Ohio State University. Accessed April 16, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1452184221.

MLA Handbook (7^th Edition):

Whiteman, Jacob T. “Active Flow Control Schemes for Bluff Body Drag Reduction.” 2016. Web. 16 Apr 2021.

Vancouver:

Whiteman JT. Active Flow Control Schemes for Bluff Body Drag Reduction. [Internet] [Masters thesis]. The Ohio State University; 2016. [cited 2021 Apr 16]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1452184221.

Council of Science Editors:

Whiteman JT. Active Flow Control Schemes for Bluff Body Drag Reduction. [Masters Thesis]. The Ohio State University; 2016. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1452184221

13. Metka, Matthew. Application of Fluidic Oscillator Separation Control to a Square-back Vehicle Model.

Degree: MS, Mechanical Engineering, 2015, The Ohio State University

URL: http://rave.ohiolink.edu/etdc/view?acc_num=osu1439205355

► Aerodynamic drag is an increasingly important factor in ground vehicle design due to its large impact on overall fuel economy. The average vehicle drag coefficient… (more)

▼ Aerodynamic drag is an increasingly important factor in ground vehicle design due to its large impact on overall fuel economy. The average vehicle drag coefficient has improved significantly since the advent of the automobile, however the marginal gains possible with traditional shape optimization are beginning to decrease. There is increased need to improve the drag coefficient as a means of reducing global fossil fuel consumption, which prompts the automotive industry to investigate additional methods of drag mitigation. One method may be the use of active flow control (AFC) aimed at large scale changes in the flowfield through the introduction of energy perturbations at strategic locations on the vehicle surface. In this study, separation control with fluidic oscillators was examined on a modified square-back Ahmed vehicle model to advance the possibility of AFC application to production vehicles. A fluidic oscillator is a simple pneumatic device that converts a steady flow input into a spatially oscillating jet. This AFC actuator was selected due to its proven separation control efficiency and robustness. Studies involving the application of fluidic oscillator separation control to simplified vehicle models have been conducted by other researchers, however the large parameter space related to oscillator effectiveness yields many unanswered questions. The goal of this work was to answer more of the relevant questions needed to bridge the gap between lab and application. The majority of this experimental study was done in a scale wind tunnel facility owned and operated by a North American automaker at a Reynolds number based on model length of 1.4x10⁶ or higher. A modified aft section containing boat-tail flaps and fluidic oscillators was added to the square-back Ahmed model and various parameter sensitivity trends were examined. Parameters of interest included flap angle, oscillator jet location, jet velocity, jet spacing, jet size, moving ground plane simulation, ride height, speeds changes, underbody turbulence, actuation symmetry, and model geometric scaling. Studies related to fluidic oscillator acoustics, separation control mechanism, and energy consumption were also conducted to build practical implementation knowledge. The results indicated that drag reduction was sensitive to many of the examined parameters. The character of the underbody flow and the use of symmetric actuation were shown to be of critical importance for optimal drag reduction, however exploitation of underbody flow modification may lend the most efficient use of actuator energy. Parameters such as Re (test speed), ride height, and simulated ground plane weakly affected the drag coefficient changes experienced with actuation. A model scaling study indicated that the actuator momentum requirements for a given drag reduction decreased as the model size was increased, partially because the number of oscillators required scales with base perimeter. A notional energy analysis suggested that the actuator energy consumption relative to drag… Advisors/Committee Members: Gregory, James (Advisor).

Subjects/Keywords: Aerospace Engineering; Automotive Engineering; Mechanical Engineering; separation control; aerodynamics; drag reduction; bluff body; Ahmed model; fluidic oscillator; bluff body wake; active flow control

…structures, either through active or passive means, is known to reduce drag and stabilize the wake… …associated drag penalty. There are many other possibilities for semi-active flow control devices… …3. Metka, M., Gregory J., 2013, “Drag Reduction on the 25° Ahmed Model Using Fluidic… …1 1.2. Aerodynamic Drag on Ground Vehicles… …2 1.3. Drag on the Ahmed Vehicle Model…

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Metka, M. (2015). Application of Fluidic Oscillator Separation Control to a Square-back Vehicle Model. (Masters Thesis). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1439205355

Chicago Manual of Style (16^th Edition):

Metka, Matthew. “Application of Fluidic Oscillator Separation Control to a Square-back Vehicle Model.” 2015. Masters Thesis, The Ohio State University. Accessed April 16, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1439205355.

MLA Handbook (7^th Edition):

Metka, Matthew. “Application of Fluidic Oscillator Separation Control to a Square-back Vehicle Model.” 2015. Web. 16 Apr 2021.

Vancouver:

Metka M. Application of Fluidic Oscillator Separation Control to a Square-back Vehicle Model. [Internet] [Masters thesis]. The Ohio State University; 2015. [cited 2021 Apr 16]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1439205355.

Council of Science Editors:

Metka M. Application of Fluidic Oscillator Separation Control to a Square-back Vehicle Model. [Masters Thesis]. The Ohio State University; 2015. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1439205355

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