subject:(reduced order modeling)

Cornell University

1. Puder, Jonathan Michael. The Rapid Analytical-FEA Technique for Reduced Simulation Times of Piezoelectric MEMS Resonators.

Degree: PhD, Mechanical Engineering, 2018, Cornell University

URL: http://hdl.handle.net/1813/59344

► Piezoelectric radio frequency microelectromechanical resonators are a promising technology for meeting the increasing demands of a crowded electromagnetic spectrum. Contour mode resonators are a potential… (more)

▼ Piezoelectric radio frequency microelectromechanical resonators are a promising technology for meeting the increasing demands of a crowded electromagnetic spectrum. Contour mode resonators are a potential technology for next generation filtering to replace current bulk acoustic wave (BAW) solutions. The lithographically defined center frequencies of contour mode resonators facilitate monolithic integration of multiple frequencies on a single chip, ideal for filter bank applications. Despite these advantages, contour mode resonator technology has not seen widespread use in commercial or military applications, with one of the main obstacles towards this end being spurious mode. Frequently, designs optimally exciting an intended mode will often excite many other modes. This can affect important performance metrics, such as the passband roll-off and group delay of filters created from these resonators, and potentially exposes the radio system to damaging high power signals. Part of the reason spurious modes remain a challenge is the lack of a rapid and wide-band simulation technique. Piezoelectric resonators typically have complex responses that must be modeled using finite element analysis (FEA) for accuracy. Conventionally, a Multiphysics harmonic analysis is run to model resonators. These simulations can take hours to days to complete. Trades must be made between frequency spacing and bandwidth for the simulation to complete in a reasonable amount of time, and can possibly miss modes. Due to the time limitations, designers often run 2D simulations which complete much faster, but will miss any out-of-plane information. To address these challenges, the wide-band Rapid Analytical-FEA Technique (RAFT) has been developed using software commonly found in research laboratories. The RAFT combines the speed of analytical analysis with the accuracy of FEA for full 3D solutions that complete orders of magnitude faster than conventional harmonic analysis while accurately modeling relevant modes. This enhanced speed is enabled by generalized expressions for the motional parameters of the modified Butterworth van-Dyke equivalent circuit: the motional resistance (Rm), inductance (Lm), and capacitance (Cm). Information from separate mechanical modal analysis and electrostatic analysis are entered into these expressions, and the frequency response is then simulated in analytical software. This accounts for the effect of all modes in the simulation bandwidth. This method is shown to improve simulations speeds by several orders of magnitude. Additionally, the RAFT enables new uses of FEA for design and analysis. Wide band simulations to assess the resonator performance far from resonance are now possible. Accurate parametric device exploration to investigate mode scaling and behavior to higher frequencies can be undertaken. The reduced simulation duration frees time for researchers to conduct studies of other critical device variables, such as the simulations of fabrication non-idealities, including electrode misalignment or sidewall… Advisors/Committee Members: Lal, Amit (chair), Erickson, David (committee member), Pollock, Clifford Raymond (committee member), Polcawich, Ronald G (committee member).

Subjects/Keywords: Piezoelectric resonator; reduced order modeling; Mechanical engineering

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APA (6^th Edition):

Puder, J. M. (2018). The Rapid Analytical-FEA Technique for Reduced Simulation Times of Piezoelectric MEMS Resonators. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/59344

Chicago Manual of Style (16^th Edition):

Puder, Jonathan Michael. “The Rapid Analytical-FEA Technique for Reduced Simulation Times of Piezoelectric MEMS Resonators.” 2018. Doctoral Dissertation, Cornell University. Accessed January 17, 2021. http://hdl.handle.net/1813/59344.

MLA Handbook (7^th Edition):

Puder, Jonathan Michael. “The Rapid Analytical-FEA Technique for Reduced Simulation Times of Piezoelectric MEMS Resonators.” 2018. Web. 17 Jan 2021.

Vancouver:

Puder JM. The Rapid Analytical-FEA Technique for Reduced Simulation Times of Piezoelectric MEMS Resonators. [Internet] [Doctoral dissertation]. Cornell University; 2018. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1813/59344.

Council of Science Editors:

Puder JM. The Rapid Analytical-FEA Technique for Reduced Simulation Times of Piezoelectric MEMS Resonators. [Doctoral Dissertation]. Cornell University; 2018. Available from: http://hdl.handle.net/1813/59344

University of Houston

2. Wassar, Taoufik. Reduced-Order Modeling of Fluid Transmission Lines.

Degree: PhD, Mechanical Engineering, 2014, University of Houston

URL: http://hdl.handle.net/10657/1654

► Solutions of fluid transients in transmission lines are very difficult to obtain, and they are generally computed using numerical techniques. In addition to their computational… (more)

▼ Solutions of fluid transients in transmission lines are very difficult to obtain, and they are generally computed using numerical techniques. In addition to their computational difficulties, the numerical methods do not directly translate into models having utility in system design, control design, and system health-monitoring particularly when the lines are parts of a fluid network system. Not surprisingly, these limitations are fully addressed by model- order reduction techniques that yield to low-dimensional linear models, which contain all the essential information. In this dissertation, a procedure for obtaining analytical low-dimensional models quantifying the dynamic behavior of confined single-phase flow in fluid transmission lines experiencing pressure and flow oscillations is formulated and presented. Solutions for the nonlinear Navier-Stokes equations are derived and written in transfer function matrix form using Laplace Transform. Two distributed parameter models for the case of laminar flow are presented. The first model is called the dissipative model and is referred to in the literature as the “exact” model. The second model is obtained using distributed lumped parameters. Since the resulting transfer functions in both models are transcendent, and therefore cannot be used for time-domain analyses, rational transfer function approximation is performed using the infinite product series expansion technique. Both models accurately predict the static and dynamic characteristics of fluid transmission lines using only few terms of the infinite products over a broad frequency range. The two models are then extended to account for turbulent flow using two different approaches. A more accurate model for turbulent flow in smooth-walled pipes is developed using an approximated weighting function. The frequency response functions of the proposed models are compared with those of an existing numerical model showing acceptable coincidence. A major benefit of the proposed models over the existing low-dimensional models is that the coefficients of the rational transfer functions can be directly calculated using analytical equations rather than table or graphs, which introduces flexibility and reduces the difficulties of modeling both laminar and turbulent flow in underdamped fluid transmission lines, while still maintaining model accuracy and complexities. Advisors/Committee Members: Franchek, Matthew A. (advisor), Liu, Dong (committee member), Song, Gangbing (committee member), Grigoriadis, Karolos M. (committee member), Mo, Yi-Lung (committee member).

Subjects/Keywords: Fluid transmission lines; Reduced-order modeling

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APA (6^th Edition):

Wassar, T. (2014). Reduced-Order Modeling of Fluid Transmission Lines. (Doctoral Dissertation). University of Houston. Retrieved from http://hdl.handle.net/10657/1654

Chicago Manual of Style (16^th Edition):

Wassar, Taoufik. “Reduced-Order Modeling of Fluid Transmission Lines.” 2014. Doctoral Dissertation, University of Houston. Accessed January 17, 2021. http://hdl.handle.net/10657/1654.

MLA Handbook (7^th Edition):

Wassar, Taoufik. “Reduced-Order Modeling of Fluid Transmission Lines.” 2014. Web. 17 Jan 2021.

Vancouver:

Wassar T. Reduced-Order Modeling of Fluid Transmission Lines. [Internet] [Doctoral dissertation]. University of Houston; 2014. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/10657/1654.

Council of Science Editors:

Wassar T. Reduced-Order Modeling of Fluid Transmission Lines. [Doctoral Dissertation]. University of Houston; 2014. Available from: http://hdl.handle.net/10657/1654

Virginia Tech

3. Koc, Birgul. Commutation Error in Reduced Order Modeling.

Degree: MS, Mathematics, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/87537

► We propose reduced order models (ROMs) for an efficient and relatively accurate numerical simulation of nonlinear systems. We use the ROM projection and the ROM… (more)

Subjects/Keywords: Reduced Order Modeling; Data-Driven Modeling; Filtering; Closure Modeling; Commutation Error

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APA (6^th Edition):

Koc, B. (2018). Commutation Error in Reduced Order Modeling. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/87537

Chicago Manual of Style (16^th Edition):

Koc, Birgul. “Commutation Error in Reduced Order Modeling.” 2018. Masters Thesis, Virginia Tech. Accessed January 17, 2021. http://hdl.handle.net/10919/87537.

MLA Handbook (7^th Edition):

Koc, Birgul. “Commutation Error in Reduced Order Modeling.” 2018. Web. 17 Jan 2021.

Vancouver:

Koc B. Commutation Error in Reduced Order Modeling. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/10919/87537.

Council of Science Editors:

Koc B. Commutation Error in Reduced Order Modeling. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/87537

Georgia Tech

4. Issac, Yanal. A quaternion approach to the modal analysis and reduced-order modeling of three-dimensional fluid systems.

Degree: PhD, Aerospace Engineering, 2020, Georgia Tech

URL: http://hdl.handle.net/1853/63702

► In 1967, Lumley derived the proper orthogonal decomposition (POD) in an attempt to provide a mathematical description of patterns that emerge in turbulent flow, which… (more)

▼ In 1967, Lumley derived the proper orthogonal decomposition (POD) in an attempt to provide a mathematical description of patterns that emerge in turbulent flow, which he called coherent structures. The POD method derived by Lumley has deep mathematical roots, is statistically based, and has analytical foundations that provide a rigorous mathematical framework for the extraction and description of coherent structures. However, it was not until 1987, when Sirovich provided a numerically tractable implementation of the POD method capable of tackling large data sets such as the ones encountered in modern day engineering problems, did the POD gain much attention. In recent years, the wide spread success of the POD method has greatly elevated the status of the POD method. Today, the POD method is considered as benchmark procedure, and is at the bedrock of modal analysis and reduced-order modeling of fluid systems. Since its inception, numerous applications, adaptions and variations of the POD have been devised. However, little attention has been paid to addressing the three-dimensional nature of fluid systems. In fact, George states that the POD is agnostic to the nature of the data, as it does not matter whether the data is velocity, pressure or temperature. The aim of this thesis was to explore a fundamentally different approach to the POD that is better suited for three-dimensional fluid systems; an approach that does not compromise the mathematical rigor associated with the concept of coherent structures defined by Lumley. The approach investigated in this thesis replaces the traditional field of real numbers \R, with a four-dimensional non-commutative division algebra ℍ, known as the quaternion division algebra. To the knowledge of the author, this thesis is the first to incorporate quaternions into Lumley's mathematical framework. The introduction of quaternions into Lumley's mathematical framework, generalizes the proper orthogonal decomposition to the quaternion proper orthogonal decomposition (QPOD) while preserving its favorable features and extending the POD to higher dimensional spaces. In the work of this thesis it was shown that a quaternion approach abstracts Lumley's mathematical representation of coherent structures at a fundamental level. These abstracted representations, defined for the first time in the work of this thesis are termed quaternion coherent structures, exhibit interesting properties and result in a fascinating phenomena termed the kaleidoscope effect which is not present in the traditional definition of coherent structures. Furthermore, it was numerically and mathematical shown that the QPOD method can better distill the essential dynamics present in a data set and can create more accurate rank-m approximations as compared the POD method. The results presented in this thesis provide compelling evidence advocating for the use of quaternions in the context of modal analysis and reduced-order modeling of three-dimensional fluid systems. In addition a… Advisors/Committee Members: Mavris, Dimitri (advisor), Silva, Walter (committee member), Eppink, Jenna (committee member), Sankar, Lakshmi (committee member), Pinon-Fischer, Olivia (committee member).

Subjects/Keywords: Reduced-order modeling; Model-order reduction; Quaternion; Proper orthogonal decomposition

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APA (6^th Edition):

Issac, Y. (2020). A quaternion approach to the modal analysis and reduced-order modeling of three-dimensional fluid systems. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/63702

Chicago Manual of Style (16^th Edition):

Issac, Yanal. “A quaternion approach to the modal analysis and reduced-order modeling of three-dimensional fluid systems.” 2020. Doctoral Dissertation, Georgia Tech. Accessed January 17, 2021. http://hdl.handle.net/1853/63702.

MLA Handbook (7^th Edition):

Issac, Yanal. “A quaternion approach to the modal analysis and reduced-order modeling of three-dimensional fluid systems.” 2020. Web. 17 Jan 2021.

Vancouver:

Issac Y. A quaternion approach to the modal analysis and reduced-order modeling of three-dimensional fluid systems. [Internet] [Doctoral dissertation]. Georgia Tech; 2020. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1853/63702.

Council of Science Editors:

Issac Y. A quaternion approach to the modal analysis and reduced-order modeling of three-dimensional fluid systems. [Doctoral Dissertation]. Georgia Tech; 2020. Available from: http://hdl.handle.net/1853/63702

Virginia Tech

5. Xie, Xuping. Large Eddy Simulation Reduced Order Models.

Degree: PhD, Mathematics, 2017, Virginia Tech

URL: http://hdl.handle.net/10919/77626

► This dissertation uses spatial filtering to develop a large eddy simulation reduced order model (LES-ROM) framework for fluid flows. Proper orthogonal decomposition is utilized to… (more)

Subjects/Keywords: Reduced Order Modeling; Large Eddy Simulation; Approximate Deconvolution; Data-Driven Modeling; Stochastic Reduced Order Model; Spatial Filtering; Finite Element; Numerical Analysis

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APA (6^th Edition):

Xie, X. (2017). Large Eddy Simulation Reduced Order Models. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77626

Chicago Manual of Style (16^th Edition):

Xie, Xuping. “Large Eddy Simulation Reduced Order Models.” 2017. Doctoral Dissertation, Virginia Tech. Accessed January 17, 2021. http://hdl.handle.net/10919/77626.

MLA Handbook (7^th Edition):

Xie, Xuping. “Large Eddy Simulation Reduced Order Models.” 2017. Web. 17 Jan 2021.

Vancouver:

Xie X. Large Eddy Simulation Reduced Order Models. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/10919/77626.

Council of Science Editors:

Xie X. Large Eddy Simulation Reduced Order Models. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/77626

UCLA

6. Gariffo, James Michael. Generalized Reduced Order Modeling of Aeroservoelastic Systems.

Degree: Mechanical Engineering, 2013, UCLA

URL: http://www.escholarship.org/uc/item/0rc0c11t

► Transonic aeroelastic and aeroservoelastic (ASE) modeling presents a significant technical and computational challenge. Flow fields with a mixture of subsonic and supersonic flow, as well… (more)

▼ Transonic aeroelastic and aeroservoelastic (ASE) modeling presents a significant technical and computational challenge. Flow fields with a mixture of subsonic and supersonic flow, as well as moving shock waves, can only be captured through high-fidelity CFD analysis. With modern computing power, it is realtively straightforward to determine the flutter boundary for a single structural configuration at a single flight condition, but problems of larger scope remain quite costly. Some such problems include characterizing a vehicle's flutter boundary over its full flight envelope, optimizing its structural weight subject to aeroelastic constraints, and designing control laws for flutter suppression. For all of these applications, reduced-order models (ROMs) offer substantial computational savings. ROM techniques in general have existed for decades, and the methodology presented in this dissertation builds on successful previous techniques to create a powerful new scheme for modeling aeroelastic systems, and predicting and interpolating their transonic flutter boundaries. In this method, linear ASE state-space models are constructed from modal structural and actuator models coupled to state-space models of the linearized aerodynamic forces through feedback loops. Flutter predictions can be made from these models through simple eigenvalue analysis of their state-transition matrices for an appropriate set of dynamic pressures. Moreover, this analysis returns the frequency and damping trend of every aeroelastic branch. In contrast, determining the critical dynamic pressure by direct time-marching CFD requires a separate run for every dynamic pressure being analyzed simply to obtain the trend for the critical branch. The present ROM methodology also includes a new model interpolation technique that greatly enhances the benefits of these ROMs. This enables predictions of the dynamic behavior of the system for flight conditions where CFD analysis has not been explicitly performed, thus making it possible to characterize the overall flutter boundary with far fewer CFD runs. A major challenge of this research is that transonic flutter boundaries can involve multiple unstable modes of different types. Multiple ROM-based studies on the ONERA M6 wing are shown indicating that in addition to classic bending-torsion (BT) flutter modes. which become unstable above a threshold dynamic pressure after two natural modes become aerodynamically coupled, some natural modes are able to extract energy from the air and become unstable by themselves. These single-mode instabilities tend to be weaker than the BT instabilities, but have near-zero flutter boundaries (exactly zero in the absence of structural damping). Examples of hump modes, which behave like natural mode instabilities before stabilizing, are also shown, as are cases where multiple instabilities coexist at a single flight condition. The result of all these instabilities is a highly sensitive flutter boundary, where small changes in Mach number, structural stiffness,…

Subjects/Keywords: Mechanical engineering; Aerospace engineering; aeroelasticity; aeroservoelasticity; flutter; reduced-order modeling; transonic

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APA (6^th Edition):

Gariffo, J. M. (2013). Generalized Reduced Order Modeling of Aeroservoelastic Systems. (Thesis). UCLA. Retrieved from http://www.escholarship.org/uc/item/0rc0c11t

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):

Gariffo, James Michael. “Generalized Reduced Order Modeling of Aeroservoelastic Systems.” 2013. Thesis, UCLA. Accessed January 17, 2021. http://www.escholarship.org/uc/item/0rc0c11t.

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

MLA Handbook (7^th Edition):

Gariffo, James Michael. “Generalized Reduced Order Modeling of Aeroservoelastic Systems.” 2013. Web. 17 Jan 2021.

Vancouver:

Gariffo JM. Generalized Reduced Order Modeling of Aeroservoelastic Systems. [Internet] [Thesis]. UCLA; 2013. [cited 2021 Jan 17]. Available from: http://www.escholarship.org/uc/item/0rc0c11t.

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

Council of Science Editors:

Gariffo JM. Generalized Reduced Order Modeling of Aeroservoelastic Systems. [Thesis]. UCLA; 2013. Available from: http://www.escholarship.org/uc/item/0rc0c11t

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

Brigham Young University

7. Hall, James B. Measurement of Thermal Diffusivities Using the Distributed Source, Finite Absorption Model.

Degree: MS, 2012, Brigham Young University

URL: https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4466&context=etd

► Thermal diffusivity in an important thermophysical property that quantifies the ratio of the rate at which heat is conducted through a material to the… (more)

▼ Thermal diffusivity in an important thermophysical property that quantifies the ratio of the rate at which heat is conducted through a material to the amount of energy stored in a material. The pulsed laser diffusion (PLD) method is a widely used technique for measuring thermal diffusivities of materials. This technique is based on the fact that the diffusivity of a sample may be inferred from measurement of the time-dependent temperature profile at a point on the surface of a sample that has been exposed to a pulse of radiant energy from a laser or flash lamp. An accepted standard approach for the PLD method is based on a simple model of a PLD measurement system. However, the standard approach is based on idealizations that are difficult to achieve in practice. Therefore, models that treat a PLD measurement system with greater fidelity are desired. The objective of this research is to develop and test a higher fidelity model that more accurately represents the spatial and temporal variations in the input power. This higher fidelity model is referred to as Distributed Source Finite Absorption (DSFA) model. The cost of the increased fidelity associated with the DSFA model is an increase in the complexity of inferring values of the thermal diffusivity. A new method of extracting values from time dependent temperature measurements based on a genetic algorithm and on reduced order modeling was developed. The primary contribution of this thesis is a detailed discussion of the development and numerical verification of this proposed new method for measuring the thermal diffusivity of various materials. Verification of the proposed new method was conducted using numerical experiments. A detailed model of a PLD system was created using advanced engineering software, and detailed simulations, including conjugate heat transfer and solution of the full Navier-Stokes equations, were used to generate multiple numerical data sets. These numerical data sets were then used to infer the thermal diffusivity and other properties of the sample using the proposed new method. These numerical data sets were also used as inputs to the standard approach. The results of this verification study show that the proposed new method is able to infer the thermal diffusivity of samples to within 4.93%, the absorption coefficient to within 10.57 % and the heat capacity of the samples to within 5.37 %. Application of the standard approach to these same data sets gave much poorer estimates of the thermal diffusivity, particularly when the absorption coefficient of the material was relatively low.

Subjects/Keywords: heat transfer; thermal diffusivity; reduced order modeling; genetic algorithm; Mechanical Engineering

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APA (6^th Edition):

Hall, J. B. (2012). Measurement of Thermal Diffusivities Using the Distributed Source, Finite Absorption Model. (Masters Thesis). Brigham Young University. Retrieved from https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4466&context=etd

Chicago Manual of Style (16^th Edition):

Hall, James B. “Measurement of Thermal Diffusivities Using the Distributed Source, Finite Absorption Model.” 2012. Masters Thesis, Brigham Young University. Accessed January 17, 2021. https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4466&context=etd.

MLA Handbook (7^th Edition):

Hall, James B. “Measurement of Thermal Diffusivities Using the Distributed Source, Finite Absorption Model.” 2012. Web. 17 Jan 2021.

Vancouver:

Hall JB. Measurement of Thermal Diffusivities Using the Distributed Source, Finite Absorption Model. [Internet] [Masters thesis]. Brigham Young University; 2012. [cited 2021 Jan 17]. Available from: https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4466&context=etd.

Council of Science Editors:

Hall JB. Measurement of Thermal Diffusivities Using the Distributed Source, Finite Absorption Model. [Masters Thesis]. Brigham Young University; 2012. Available from: https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4466&context=etd

Clemson University

8. Pollard, Beau. Improving Swimming Performance and Flow Sensing by Incorporating Passive Mechanisms.

Degree: PhD, Mechanical Engineering, 2020, Clemson University

URL: https://tigerprints.clemson.edu/all_dissertations/2624

► As water makes up approximately 70% of the Earth's surface, humans have expanded operations into aquatic environments out of both necessity and a desire… (more)

▼ As water makes up approximately 70% of the Earth's surface, humans have expanded operations into aquatic environments out of both necessity and a desire to gain potential innate benefits. This expansion into aquatic environments has consequently developed a need for cost-effective and safe underwater monitoring, surveillance, and inspection, which are missions that autonomous underwater vehicles are particularly well suited for. Current autonomous underwater vehicles vastly underperform when compared to biological swimmers, which has prompted researchers to develop robots inspired by natural swimmers. One such robot is designed, built, tested, and numerically simulated in this thesis to gain insight into the benefits of passive mechanisms and the development of reduced-order models. Using a bio-inspired robot with multiple passive tails I demonstrate herein the relationship between maneuverability and passive appendages. I found that the allowable rotation angle, relative to the main body, of the passive tails corresponds to an increase in maneuverability. Using panel method simulations I determined that the increase in maneuverability was directly related to the change in hydrodynamic moment caused by modulating the circulation sign and location of the shed vortex wake. The identification of this hydrodynamic benefit generalizes the results and applies to a wide range of robots that utilize vortex shedding through tail flapping or body undulations to produce locomotion. Passive appendages are a form of embodied control, which manipulates the fluid-robot interaction and analogously such interaction can be sensed from the dynamics of the body. Body manipulation is a direct result of pressure fluctuations inherent in the surrounding fluid flow. These pressure fluctuations are unique to specific flow conditions, which may produce distinguishable time series kinematics of the appendage. Using a bio-inspired foil tethered in a water tunnel I classified different vortex wakes with the foil's kinematic data. This form of embodied feedback could be used for the development of control algorithms dedicated to obstacle avoidance, tracking, and station holding. Mathematical models of autonomous vehicles are necessary to implement advanced control algorithms such as path planning. Models that accurately and efficiently simulate the coupled fluid-body interaction in freely swimming aquatic robots are difficult to determine due, in part, to the complex nature of fluids. My colleagues and I approach this problem by relating the swimming robot to a terrestrial vehicle known as the Chaplygin sleigh. Using our novel technique we determined an analogous Chaplygin sleigh model that accurately represents the steady-state dynamics of our swimming robot. We additionally used the subsequent model for heading and velocity control in panel method simulations. This work was inspired by the similarities in constraints and velocity space limit cycles of the swimmer and the Chaplygin sleigh, which makes this… Advisors/Committee Members: Phanindra Tallapragada, Ardalan Vahidi, Yue Wang, John Wagner.

Subjects/Keywords: Bio-inspiration; Flow sensing; Reduced order modeling; Robotics; Vortex shedding

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APA (6^th Edition):

Pollard, B. (2020). Improving Swimming Performance and Flow Sensing by Incorporating Passive Mechanisms. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/2624

Chicago Manual of Style (16^th Edition):

Pollard, Beau. “Improving Swimming Performance and Flow Sensing by Incorporating Passive Mechanisms.” 2020. Doctoral Dissertation, Clemson University. Accessed January 17, 2021. https://tigerprints.clemson.edu/all_dissertations/2624.

MLA Handbook (7^th Edition):

Pollard, Beau. “Improving Swimming Performance and Flow Sensing by Incorporating Passive Mechanisms.” 2020. Web. 17 Jan 2021.

Vancouver:

Pollard B. Improving Swimming Performance and Flow Sensing by Incorporating Passive Mechanisms. [Internet] [Doctoral dissertation]. Clemson University; 2020. [cited 2021 Jan 17]. Available from: https://tigerprints.clemson.edu/all_dissertations/2624.

Council of Science Editors:

Pollard B. Improving Swimming Performance and Flow Sensing by Incorporating Passive Mechanisms. [Doctoral Dissertation]. Clemson University; 2020. Available from: https://tigerprints.clemson.edu/all_dissertations/2624

Georgia Tech

9. Bozeman, Michael Dwain. A reduced-order modeling methodology for the multidisciplinary design and analysis of boundary layer ingestion configurations.

Degree: PhD, Aerospace Engineering, 2019, Georgia Tech

URL: http://hdl.handle.net/1853/62322

► In response to the increasingly stringent requirements for subsonic transport aircraft, NASA has established aggressive goals for the noise, emissions, and fuel burn of the… (more)

▼ In response to the increasingly stringent requirements for subsonic transport aircraft, NASA has established aggressive goals for the noise, emissions, and fuel burn of the next generations of aircraft. This has led to the investigation of a variety of unconventional configurations and new technologies. Boundary Layer Ingestion (BLI) propulsion has been identified as a promising technology to reduce fuel burn. Preliminary studies show that BLI propulsion can offer 3-12% reduction in fuel burn, depending on the configuration. Traditionally, the design and analysis of the airframe and propulsion system has been performed in a decoupled manner. For BLI configurations, the propulsion system is tightly integrated into the airframe resulting in strong interactions between the airframe aerodynamics and propulsion system performance. As a result, the design and analysis of BLI configurations requires coupled multidisciplinary analysis (MDA) consisting of an aerodynamic analysis in an iterative loop with a propulsion system analysis. This is a very expensive analysis considering the requirement for high-fidelity models. Additionally, the design of highly-coupled configurations cannot rely solely on intuition to make design decisions. Advanced methods including Multidisciplinary Analysis and Optimization (MDAO) and design space exploration are needed to allow for the design decisions to be made based directly on a system-level objective (e.g., fuel burn) and to allow for design studies to provide insight into the multidisciplinary trades associated with BLI configurations. However, MDAO and design space exploration using coupled, high-fidelity analysis models are not practical. In this work, reduced-order modeling (ROM) is proposed as a potential solution to reduce the computational cost associated with the coupled MDA of BLI configurations and to enable these advanced design methods. An interpolation-based POD ROM is developed based on the CFD analysis to allow for predictions of the aerodynamics over a range of propulsor operating conditions for a simplified tail-cone thruster (TCT) configuration. The resulting ROM is then coupled to a propulsion model to perform ROM-based, coupled MDA. Finally, the ROM-based, coupled MDA approach is employed for coupled MDAO to assess the performance benefit offered relative to equivalent CFD- and adjoint-based approaches. The results show that the ROM-based, coupled MDA approach offers an improvement in performance relative to the current state of the art. Relative to the equivalent CFD-based approach, the ROM-based, coupled MDA method demonstrated significant computational savings for even a single optimization. However, the ROM-based approach requires multiple optimizations to offer a computational benefit over the adjoint-based approach. This result highlights the benefit of the proposed approach for optimization studies and design space exploration. Advisors/Committee Members: Mavris, Dimitri N. (advisor), Tai, Jimmy C. (committee member), Carter, Melissa B. (committee member), Ordaz, Irian (committee member), Smith, Marilyn J. (committee member).

Subjects/Keywords: Computational fluid dynamics; Boundary layer ingestion; Reduced-order modeling

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APA (6^th Edition):

Bozeman, M. D. (2019). A reduced-order modeling methodology for the multidisciplinary design and analysis of boundary layer ingestion configurations. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/62322

Chicago Manual of Style (16^th Edition):

Bozeman, Michael Dwain. “A reduced-order modeling methodology for the multidisciplinary design and analysis of boundary layer ingestion configurations.” 2019. Doctoral Dissertation, Georgia Tech. Accessed January 17, 2021. http://hdl.handle.net/1853/62322.

MLA Handbook (7^th Edition):

Bozeman, Michael Dwain. “A reduced-order modeling methodology for the multidisciplinary design and analysis of boundary layer ingestion configurations.” 2019. Web. 17 Jan 2021.

Vancouver:

Bozeman MD. A reduced-order modeling methodology for the multidisciplinary design and analysis of boundary layer ingestion configurations. [Internet] [Doctoral dissertation]. Georgia Tech; 2019. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1853/62322.

Council of Science Editors:

Bozeman MD. A reduced-order modeling methodology for the multidisciplinary design and analysis of boundary layer ingestion configurations. [Doctoral Dissertation]. Georgia Tech; 2019. Available from: http://hdl.handle.net/1853/62322

University of Notre Dame

10. Teng Wu. Nonlinear Bluff-Body Aerodynamics</h1>.

Degree: Civil Engineering and Geological Sciences, 2013, University of Notre Dame

URL: https://curate.nd.edu/show/wm117m03w99

► Wind induced effects on structures governed by the Navier-Stokes equations are not adequately represented by the conventional linear analysis framework. This shortcoming is becoming… (more)

▼ Wind induced effects on structures governed by the Navier-Stokes equations are not adequately represented by the conventional linear analysis framework. This shortcoming is becoming important for contemporary structures, as their increasing span-lengths and heights make them more sensitive to nonlinear and unsteady aerodynamic/aeroelastic load effects. To address this challenge this study focuses on responding to following key questions: (1) What are the typical nonlinear behaviors observed from wind tunnel studies and full-scale observations and their underlying physics? (2) What are the effects of nonlinearity and unsteadiness on bluff-body aerodynamics? (3) What is the ability of existing nonlinear models to capture nonlinear and unsteady effects? (4) Is it possible to go beyond the current nonlinear models, and establish more effective nonlinear unsteady low-dimensional modeling techniques? In this context, the higher-order spectral approach is utilized to identify nonlinearity in bluff-body aerodynamics observed in wind-tunnel experiments. Physical sources of aerodynamic nonlinearities are investigated by analyzing the aerodynamic forces on a suite of cross-sections obtained through computational fluid dynamics (CFD). The effects of nonlinearity and unsteadiness on bluff-body aerodynamics are evaluated by comparing aerodynamic responses derived from different analytical models. Current models set in the conventional analysis framework are reviewed to understand their ability in simulating nonlinear unsteady aerodynamics; also, an improved model within the same framework is proposed. Several advanced low-dimensional modeling techniques, characterized by different levels of analysis of nonlinearity and unsteadiness, are then proposed. These include an approach based on artificial neural networks, a nonlinear moving average model (within the framework of Volterra theory), and a Volterra series-based model in which the kernels are identified using impulse functions. The fidelity with which the proposed approaches are able to simulate nonlinear bluff-body aerodynamics and aeroelasticity is verified through wind-tunnel or CFD-based data. This study allowed to better understand the nonlinear and unsteady features of bluff-body aerodynamics and aeroelasticity and to establish an effective analysis framework which, although mainly developed in the context of cable-supported bridges, has also immediate applications to stay cables, super-tall buildings, airfoils in the transonic region or with high angle of attack, and wind turbines near dynamic stall conditions. Advisors/Committee Members: Ahsan Kareem, Committee Chair, Flint Thomas, Committee Member, Yaojun Ge, Committee Member, Meng Wang, Committee Member, Alexandros Taflanidis, Committee Member.

Subjects/Keywords: fluid-structure interaction; reduced-order modeling; bridge; nonlinearity; aerodynamics; aeroelasticity

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APA (6^th Edition):

Wu, T. (2013). Nonlinear Bluff-Body Aerodynamics</h1>. (Thesis). University of Notre Dame. Retrieved from https://curate.nd.edu/show/wm117m03w99

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):

Wu, Teng. “Nonlinear Bluff-Body Aerodynamics</h1>.” 2013. Thesis, University of Notre Dame. Accessed January 17, 2021. https://curate.nd.edu/show/wm117m03w99.

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

MLA Handbook (7^th Edition):

Wu, Teng. “Nonlinear Bluff-Body Aerodynamics</h1>.” 2013. Web. 17 Jan 2021.

Vancouver:

Wu T. Nonlinear Bluff-Body Aerodynamics</h1>. [Internet] [Thesis]. University of Notre Dame; 2013. [cited 2021 Jan 17]. Available from: https://curate.nd.edu/show/wm117m03w99.

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

Council of Science Editors:

Wu T. Nonlinear Bluff-Body Aerodynamics</h1>. [Thesis]. University of Notre Dame; 2013. Available from: https://curate.nd.edu/show/wm117m03w99

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

University of Illinois – Urbana-Champaign

11. Kurt, Mehmet. Identification, reduced order modeling and model updating of nonlinear mechanical systems.

Degree: PhD, 0133, 2014, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/50609

► In this dissertation, we propose a new method for global/local nonlinear system identification, reduced order modeling and nonlinear model updating, applicable to a broad class… (more)

▼ In this dissertation, we propose a new method for global/local nonlinear system identification, reduced order modeling and nonlinear model updating, applicable to a broad class of dynamical systems. The global aspect of the approach is based on analyzing the free and forced dynamics of the system in the frequency-energy domain through the construction of free decay or steady-state frequency-energy plots (FEPs). The local aspect of the approach considers specific damped transitions and leads to low-dimensional reduced order models that accurately reproduce these transitions. The nonlinear model updating strategy is based on analyzing the system in the frequency-energy domain by constructing Hamiltonian or forced and damped frequency-energy plots (FEPs). These plots depict the steady-state solutions of the systems based on their frequency-energy dependencies. The backbone branches, branches that correspond to 1:1 resonances, are calculated analytically (for fewer DOFs) or numerically (e.g., shooting method). The system parameters are then characterized and updated by matching these backbone branches with the frequency-energy dependence of the given system by using experimental/computational data. The main advantage of our approach is that we do not assume any type of nonlinearity model a priori, and the system model is updated solely based on numerical simulations and/or experimental results. As such, the approach is applicable to a broad class of nonlinear systems, including systems with strong nonlinearities and non-smooth effects, as will be shown in this dissertation. For larger scale systems, model reduction techniques (e.g., Guyan reduction) are applied to construct reduced order models of the system to which the aforementioned methods are applied. Advisors/Committee Members: Vakakis, Alexander F. (advisor), Vakakis, Alexander F. (Committee Chair), Bergman, Lawrence A. (committee member), McFarland, Donald M. (committee member), Alleyne, Andrew G. (committee member).

Subjects/Keywords: Nonlinear System Identification; Nonlinear Model Updating; Reduced-Order Modeling

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APA (6^th Edition):

Kurt, M. (2014). Identification, reduced order modeling and model updating of nonlinear mechanical systems. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/50609

Chicago Manual of Style (16^th Edition):

Kurt, Mehmet. “Identification, reduced order modeling and model updating of nonlinear mechanical systems.” 2014. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 17, 2021. http://hdl.handle.net/2142/50609.

MLA Handbook (7^th Edition):

Kurt, Mehmet. “Identification, reduced order modeling and model updating of nonlinear mechanical systems.” 2014. Web. 17 Jan 2021.

Vancouver:

Kurt M. Identification, reduced order modeling and model updating of nonlinear mechanical systems. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2014. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/2142/50609.

Council of Science Editors:

Kurt M. Identification, reduced order modeling and model updating of nonlinear mechanical systems. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2014. Available from: http://hdl.handle.net/2142/50609

Boise State University

12. Rosin, Sean. Reduced Order Modeling for Virtual Building Commissioning.

Degree: 2018, Boise State University

URL: https://scholarworks.boisestate.edu/td/1411

► Model order reduction can help reduce the time and monetary constraints associated with building commissioning and significantly decrease overall building energy consumption through virtual commissioning.… (more)

Subjects/Keywords: building; commissioning; reduced; order; modeling; virtual; Acoustics, Dynamics, and Controls

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APA (6^th Edition):

Rosin, S. (2018). Reduced Order Modeling for Virtual Building Commissioning. (Thesis). Boise State University. Retrieved from https://scholarworks.boisestate.edu/td/1411

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):

Rosin, Sean. “Reduced Order Modeling for Virtual Building Commissioning.” 2018. Thesis, Boise State University. Accessed January 17, 2021. https://scholarworks.boisestate.edu/td/1411.

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

MLA Handbook (7^th Edition):

Rosin, Sean. “Reduced Order Modeling for Virtual Building Commissioning.” 2018. Web. 17 Jan 2021.

Vancouver:

Rosin S. Reduced Order Modeling for Virtual Building Commissioning. [Internet] [Thesis]. Boise State University; 2018. [cited 2021 Jan 17]. Available from: https://scholarworks.boisestate.edu/td/1411.

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

Council of Science Editors:

Rosin S. Reduced Order Modeling for Virtual Building Commissioning. [Thesis]. Boise State University; 2018. Available from: https://scholarworks.boisestate.edu/td/1411

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

Georgia Tech

13. Prosser, Daniel T. Advanced computational techniques for unsteady aerodynamic-dynamic interactions of bluff bodies.

Degree: PhD, Aerospace Engineering, 2015, Georgia Tech

URL: http://hdl.handle.net/1853/53899

► Interactions between the aerodynamics and dynamics of bluff bodies are important in many engineering applications, including suspension bridges, tall buildings, oil platforms, wind turbine towers,… (more)

▼ Interactions between the aerodynamics and dynamics of bluff bodies are important in many engineering applications, including suspension bridges, tall buildings, oil platforms, wind turbine towers, air drops, and construction with cranes. In the rotorcraft field, bluff bodies are commonly suspended underneath the vehicle by tethers. This approach is often the only practical way to deliver a payload in a reasonable amount of time in disaster relief efforts, search-and-rescue operations, and military operations. However, currently a fundamental understanding of the aerodynamics of these bluff bodies is lacking, and accurate dynamic simulation models for predicting the safe flying speed are not available. In order to address these shortcomings, two main advancements are presented in this thesis. The aerodynamics of several three-dimensional canonical bluff bodies are examined over a range of Reynolds numbers representative of wind-tunnel-scale to full-scale models. Numerical experiments are utilized, with a focus on uncertainty analysis and validation of the computations. Mean and unsteady forces and moments for these bluff bodies have been evaluated, and empirical models of the shear layer characteristics have been extracted to quantify the behaviors and provide predictive capability. In addition, a physics-based reduced-order simulation model has been developed for bluff bodies. The physics-based approach is necessary to ensure that the predicted behavior of new configurations is accurate, and it is made possible by the breakthroughs in three-dimensional bluff body aerodynamics presented in this thesis. The integrated aerodynamic forces and moments and dynamic behavior predicted by model are extensively validated with data from wind tunnels, flight tests, and high-fidelity computations. Furthermore, successful stability predictions for tethered loads are demonstrated. The model is applicable to the simulation of any generic bluff body configuration, is readily extensible, and has low computational cost. Advisors/Committee Members: Smith, Marilyn (advisor), Costello, Mark (committee member), Schrage, Daniel (committee member), Glezer, Ari (committee member), Moulton, Marvin (committee member), Thompson, Thomas (committee member).

Subjects/Keywords: Computational fluid dynamics; Reduced-order modeling; Tethered loads; Rotorcraft; Bluff bodies

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APA (6^th Edition):

Prosser, D. T. (2015). Advanced computational techniques for unsteady aerodynamic-dynamic interactions of bluff bodies. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53899

Chicago Manual of Style (16^th Edition):

Prosser, Daniel T. “Advanced computational techniques for unsteady aerodynamic-dynamic interactions of bluff bodies.” 2015. Doctoral Dissertation, Georgia Tech. Accessed January 17, 2021. http://hdl.handle.net/1853/53899.

MLA Handbook (7^th Edition):

Prosser, Daniel T. “Advanced computational techniques for unsteady aerodynamic-dynamic interactions of bluff bodies.” 2015. Web. 17 Jan 2021.

Vancouver:

Prosser DT. Advanced computational techniques for unsteady aerodynamic-dynamic interactions of bluff bodies. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1853/53899.

Council of Science Editors:

Prosser DT. Advanced computational techniques for unsteady aerodynamic-dynamic interactions of bluff bodies. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53899

University of Maryland

14. Forstall, Virginia Hardy. Iterative Solution Methods for Reduced-Order Models of Parameterized Partial Differential Equations.

Degree: Applied Mathematics and Scientific Computation, 2015, University of Maryland

URL: http://hdl.handle.net/1903/17232

► This dissertation considers efficient computational algorithms for solving parameterized discrete partial differential equations (PDEs) using techniques of reduced-order modeling. Parameterized equations of this type arise… (more)

Subjects/Keywords: Applied mathematics; iterative solvers; Krylov subspace recycling; reduced-order modeling

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APA (6^th Edition):

Forstall, V. H. (2015). Iterative Solution Methods for Reduced-Order Models of Parameterized Partial Differential Equations. (Thesis). University of Maryland. Retrieved from http://hdl.handle.net/1903/17232

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):

Forstall, Virginia Hardy. “Iterative Solution Methods for Reduced-Order Models of Parameterized Partial Differential Equations.” 2015. Thesis, University of Maryland. Accessed January 17, 2021. http://hdl.handle.net/1903/17232.

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

MLA Handbook (7^th Edition):

Forstall, Virginia Hardy. “Iterative Solution Methods for Reduced-Order Models of Parameterized Partial Differential Equations.” 2015. Web. 17 Jan 2021.

Vancouver:

Forstall VH. Iterative Solution Methods for Reduced-Order Models of Parameterized Partial Differential Equations. [Internet] [Thesis]. University of Maryland; 2015. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1903/17232.

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

Council of Science Editors:

Forstall VH. Iterative Solution Methods for Reduced-Order Models of Parameterized Partial Differential Equations. [Thesis]. University of Maryland; 2015. Available from: http://hdl.handle.net/1903/17232

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

Virginia Tech

15. Xie, Xuping. Approximate Deconvolution Reduced Order Modeling.

Degree: MS, Mathematics, 2015, Virginia Tech

URL: http://hdl.handle.net/10919/78043

► This thesis proposes a large eddy simulation reduced order model (LES-ROM) framework for the numerical simulation of realistic flows. In this LES-ROM framework, the proper… (more)

Subjects/Keywords: approximate deconvolution; large eddy simulation; reduced order modeling; inverse problems; regularization

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APA (6^th Edition):

Xie, X. (2015). Approximate Deconvolution Reduced Order Modeling. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78043

Chicago Manual of Style (16^th Edition):

Xie, Xuping. “Approximate Deconvolution Reduced Order Modeling.” 2015. Masters Thesis, Virginia Tech. Accessed January 17, 2021. http://hdl.handle.net/10919/78043.

MLA Handbook (7^th Edition):

Xie, Xuping. “Approximate Deconvolution Reduced Order Modeling.” 2015. Web. 17 Jan 2021.

Vancouver:

Xie X. Approximate Deconvolution Reduced Order Modeling. [Internet] [Masters thesis]. Virginia Tech; 2015. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/10919/78043.

Council of Science Editors:

Xie X. Approximate Deconvolution Reduced Order Modeling. [Masters Thesis]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/78043

Virginia Tech

16. Names, Benjamin Joseph. An Efficient Reduced Order Modeling Method for Analyzing Composite Beams Under Aeroelastic Loading.

Degree: MS, Aerospace Engineering, 2016, Virginia Tech

URL: http://hdl.handle.net/10919/71676

► Composite materials hold numerous advantages over conventional aircraft grade metals. These include high stiffness/strength-to-weight ratios and beneficial stiffness coupling typically used for aeroelastic tailoring. Due… (more)

▼ Composite materials hold numerous advantages over conventional aircraft grade metals. These include high stiffness/strength-to-weight ratios and beneficial stiffness coupling typically used for aeroelastic tailoring. Due to the complexity of modeling composites, designers often select safe, simple geometry and layup schedules for their wing/blade cross-sections. An example of this might be a box-beam made up of 4 laminates, all of which are quasi-isotropic. This results in neglecting more complex designs that might yield a more effective solution, but require a greater analysis effort. The present work aims to show that the incorporation of complex cross-sections are feasible in the early design process through the use of cross-sectional analysis in conjunction with Timoshenko beam theory. It is important to note that in general, these cross-sections can be inhomogeneous: made up of any number of various materials systems. In addition, these materials could all be anisotropic in nature. The geometry of the cross-sections can take on any shape. Through this reduced order modeling scheme, complex structures can be reduced to 1 dimensional beams. With this approach, the elastic behavior of the structure can be captured, while also allowing for accurate 3D stress and strain recovery. This efficient structural modeling would be ideal in the preliminary design optimization of a wing structure. Furthermore, in conjunction with an efficient unsteady aerodynamic model such as the doublet lattice method, the dynamic aeroelastic stability can also be efficiently captured. This work introduces a comprehensively verified, open source python API called AeroComBAT (Aeroelastic Composite Beam Analysis Tool). By leveraging cross-sectional analysis, Timoshenko beam theory, and unsteady doublet-lattice method, this package is capable of efficiently conducting linear static structural analysis, normal mode analysis, and dynamic aeroelastic analysis. AeroComBAT can have a significant impact on the design process of a composite structure, and would be ideally implemented as part of a design optimization. Advisors/Committee Members: Patil, Mayuresh J. (committeechair), Seidel, Gary D. (committee member), Canfield, Robert Arthur (committee member).

Subjects/Keywords: Composites; Reduced Order Modeling; Stress Analysis; Aeroelasticity; Flutter

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APA (6^th Edition):

Names, B. J. (2016). An Efficient Reduced Order Modeling Method for Analyzing Composite Beams Under Aeroelastic Loading. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/71676

Chicago Manual of Style (16^th Edition):

Names, Benjamin Joseph. “An Efficient Reduced Order Modeling Method for Analyzing Composite Beams Under Aeroelastic Loading.” 2016. Masters Thesis, Virginia Tech. Accessed January 17, 2021. http://hdl.handle.net/10919/71676.

MLA Handbook (7^th Edition):

Names, Benjamin Joseph. “An Efficient Reduced Order Modeling Method for Analyzing Composite Beams Under Aeroelastic Loading.” 2016. Web. 17 Jan 2021.

Vancouver:

Names BJ. An Efficient Reduced Order Modeling Method for Analyzing Composite Beams Under Aeroelastic Loading. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/10919/71676.

Council of Science Editors:

Names BJ. An Efficient Reduced Order Modeling Method for Analyzing Composite Beams Under Aeroelastic Loading. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/71676

17. Dawson, Scott Thomas McGregor. Reduced-order modeling of fluids systems, with applications in unsteady aerodynamics .

Degree: PhD, 2017, Princeton University

URL: http://arks.princeton.edu/ark:/88435/dsp01p2676z051

► This thesis focuses on two major themes: modeling and understanding the dynamics of rapidly pitching airfoils, and developing methods that can be used to extract… (more)

▼ This thesis focuses on two major themes: modeling and understanding the dynamics of rapidly pitching airfoils, and developing methods that can be used to extract models and pertinent features from datasets obtained in the study of these and other systems in fluid mechanics and aerodynamics. Much of the work utilizes in some capacity dynamic mode decomposition (DMD), a recently developed method to extract dynamical features and models from data. The investigation of pitching airfoils includes both wind tunnel experiments and direct numerical simulations. Experiments are performed on a NACA 0012 airfoil undergoing rapid pitching motion, with the focus on developing a switched linear modeling framework that can accurately predict unsteady aerodynamic forces and pressure distributions throughout arbitrary pitching motions. Numerical simulations are used to study the behavior of sinusoidally pitching airfoils. By systematically varying the amplitude, frequency, mean angle and axis of pitching, a comprehensive database of results is acquired, from which interesting regions in parameter space are identified and studied. Attention is given to pitching at "preferred" frequencies, where vortex shedding in the wake is excited or amplified, leading to larger lift forces. More generally, the ability to extract nonlinear models that describe the behavior of complex fluids systems can assist in not only understanding the dominant features of such systems, but also to achieve accurate prediction and control. One potential avenue to achieve this objective is through numerical approximation of the Koopman operator, an infinite-dimensional linear operator capable of describing finite-dimensional nonlinear systems, such as those that might describe the dominant dynamics of fluids systems. This idea is explored by showing that algorithms designed to approximate the Koopman operator can indeed be utilized to accurately model nonlinear fluids systems, even when the data available is limited or noisy. Data-driven algorithms can be adversely affected by noisy data. Focusing on DMD, it is shown analytically that the algorithm is biased to sensor noise, which explains a previously observed sensitivity to noisy data. Using this finding, a number of modifications to DMD are proposed, which all give better approximations of the true dynamics using noise-corrupted data. Advisors/Committee Members: Rowley, Clarence W (advisor).

Subjects/Keywords: Data-driven modeling; Dynamic mode decomposition; Fluid mechanics; Reduced-order modeling; System identification; Unsteady aerodynamics

11 more images…

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APA (6^th Edition):

Dawson, S. T. M. (2017). Reduced-order modeling of fluids systems, with applications in unsteady aerodynamics . (Doctoral Dissertation). Princeton University. Retrieved from http://arks.princeton.edu/ark:/88435/dsp01p2676z051

Chicago Manual of Style (16^th Edition):

Dawson, Scott Thomas McGregor. “Reduced-order modeling of fluids systems, with applications in unsteady aerodynamics .” 2017. Doctoral Dissertation, Princeton University. Accessed January 17, 2021. http://arks.princeton.edu/ark:/88435/dsp01p2676z051.

MLA Handbook (7^th Edition):

Dawson, Scott Thomas McGregor. “Reduced-order modeling of fluids systems, with applications in unsteady aerodynamics .” 2017. Web. 17 Jan 2021.

Vancouver:

Dawson STM. Reduced-order modeling of fluids systems, with applications in unsteady aerodynamics . [Internet] [Doctoral dissertation]. Princeton University; 2017. [cited 2021 Jan 17]. Available from: http://arks.princeton.edu/ark:/88435/dsp01p2676z051.

Council of Science Editors:

Dawson STM. Reduced-order modeling of fluids systems, with applications in unsteady aerodynamics . [Doctoral Dissertation]. Princeton University; 2017. Available from: http://arks.princeton.edu/ark:/88435/dsp01p2676z051

Princeton University

18. Zhang, Hao. Data-driven Modeling for Fluid Dynamics and Control .

Degree: PhD, 2020, Princeton University

URL: http://arks.princeton.edu/ark:/88435/dsp0108612r49q

► One of the most critical tasks in fluid dynamics and control is to build simple, low-order, and accurate models. The models are essential for understanding… (more)

▼ One of the most critical tasks in fluid dynamics and control is to build simple, low-order, and accurate models. The models are essential for understanding dynamics and control. However, in many cases, the models are either unknown or too complicated to be useful. As an example, fluid flows are governed by Navier-Stokes equations (NSE), which remain intractable for real-time applications. Meanwhile, with increasing computational power and advances in experimental and numerical methods, researchers have access to much more data about dynamical systems. For instance, computational fluid dynamics (CFD) produces tons of data, but the data have not been fully utilized. Data-driven modeling addresses these challenges by learning dynamical system models from data. This thesis focuses on data-driven modeling methods for applications in fluid dynamics and control. First, we propose an evaluation criterion to quantify the accuracy of dynamic mode decomposition (DMD), a data-driven algorithm for extracting spatial and temporal features about dynamical systems from data. DMD is a numerical approximation to the linear Koopman operator associated with a dynamical system. By exploiting this connection, the accuracy criterion is purely data-driven and physically meaningful. It also applies to other variants of DMD algorithms and assists in model selection. Second, fast algorithms are developed for online dynamic mode decomposition (ODMD). Given real-time measurement about a dynamical system, this algorithm efficiently updates an adaptive model upon each new snapshot. It reduces both the computational time and memory requirements by order of magnitudes compared with existing methods. ODMD algorithm can be modified to gradually forget old data, which enables faster tracking of dynamics. ODMD also extends to both linear and nonlinear system identification, where control is included. Finally, we study the input-output response of a separated flow past a flat plate. The analysis is based on the frequency-domain transfer function of the linearized NSE about the mean flow. The control input is body forcing, and the output is the flow field. This analysis sheds light on the optimal control placement and reveals that the trailing edge separation bubble is most sensitive to streamwise body force (control) in upstream of the separation point. Advisors/Committee Members: Rowley, Clarence W (advisor).

Subjects/Keywords: Control; Data-driven modeling; Dynamical systems; Fluid dynamics; Model reduction; Reduced-order modeling

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APA (6^th Edition):

Zhang, H. (2020). Data-driven Modeling for Fluid Dynamics and Control . (Doctoral Dissertation). Princeton University. Retrieved from http://arks.princeton.edu/ark:/88435/dsp0108612r49q

Chicago Manual of Style (16^th Edition):

Zhang, Hao. “Data-driven Modeling for Fluid Dynamics and Control .” 2020. Doctoral Dissertation, Princeton University. Accessed January 17, 2021. http://arks.princeton.edu/ark:/88435/dsp0108612r49q.

MLA Handbook (7^th Edition):

Zhang, Hao. “Data-driven Modeling for Fluid Dynamics and Control .” 2020. Web. 17 Jan 2021.

Vancouver:

Zhang H. Data-driven Modeling for Fluid Dynamics and Control . [Internet] [Doctoral dissertation]. Princeton University; 2020. [cited 2021 Jan 17]. Available from: http://arks.princeton.edu/ark:/88435/dsp0108612r49q.

Council of Science Editors:

Zhang H. Data-driven Modeling for Fluid Dynamics and Control . [Doctoral Dissertation]. Princeton University; 2020. Available from: http://arks.princeton.edu/ark:/88435/dsp0108612r49q

University of Alberta

19. Wang, Zichuan. Model order reduction and boundary control of incompressible Boussinesq flow.

Degree: MS, Department of Mechanical Engineering, 2016, University of Alberta

URL: https://era.library.ualberta.ca/files/cgm80hv38r

► The time evolution of a two dimensional incompressible, density stratified, Boussinesq flow in a rectangular cavity is numerically simulated for a range of parameters. Boundary… (more)

▼ The time evolution of a two dimensional incompressible, density stratified, Boussinesq flow in a rectangular cavity is numerically simulated for a range of parameters. Boundary control is then implemented along the upper boundary by adjusting the fluid density. More specifically, the top boundary condition of the cavity is a fixed function of space that is modulated by the control input. The resulting numerical simulation for the fluid density and velocity is computed using finite differences in the vertical direction and a spectral method in the horizontal direction. To develop the control strategy, the flow is simulated and a sequence of snapshots of the density and velocity fields are collected. Then, a reduced order modelling method suitable for a linear quadratic regulator (LQR) of the Boussinesq flow is developed using the proper orthogonal decomposition (POD)/Galerkin approach. The reduced order model is obtained by projecting the governing equations of the flow onto the sub space spanned by a finite number of basis functions obtained using the method of snapshots. For the flow in question, the POD method based on the snapshots yields 6 POD modes which capture 99% of the flow energy. In turn, the boundary control is transferred to the governing equations using Duhamel's principle so that the resulting equations contain the control input. The feasibility of this method is assessed using a LQR boundary controller that is designed based on the reduced order model. The cost functional which is minimized in the LQR control design is defined to be the squared norm of the difference between the actual density field and the desired density field in the cavity. The weighting parameter of the cost functional is found to play a critical role in the process of controller design. To judge the effectiveness of the control, two metrics η_a and η_r are introduced. η_a denotes the absolute effectiveness of the LQR controller and is a metric of the controller's ability to drive the system to the final desired state. Conversely η_r denotes the relative effectiveness of the LQR controller and is a metric of the improvement of the LQR controller compared to an open-loop controller. For the control cases tested, the LQR controller is found to have η_a =96.7% and η_r = 22.2% in the best case for the steady state starting configurations, and η_a =99.3% and η_r = 47.9% for representative transient cases. η_r is more than doubled in the comparison between the steady case and the transient case. This indicates that the LQR controller is able to reject complex transient flow much better than the open-loop controller. In conclusion, a relatively simple feedback control scheme applied on the boundary of a turbulent flow improves the performance in regulating the density field to its desired final state compared to open-loop control.

Subjects/Keywords: Linear quadratic regulator; Galerkin method; Proper orthogonal decomposition; boundary control; Reduced order modeling

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

APA (6^th Edition):

Wang, Z. (2016). Model order reduction and boundary control of incompressible Boussinesq flow. (Masters Thesis). University of Alberta. Retrieved from https://era.library.ualberta.ca/files/cgm80hv38r

Chicago Manual of Style (16^th Edition):

Wang, Zichuan. “Model order reduction and boundary control of incompressible Boussinesq flow.” 2016. Masters Thesis, University of Alberta. Accessed January 17, 2021. https://era.library.ualberta.ca/files/cgm80hv38r.

MLA Handbook (7^th Edition):

Wang, Zichuan. “Model order reduction and boundary control of incompressible Boussinesq flow.” 2016. Web. 17 Jan 2021.

Vancouver:

Wang Z. Model order reduction and boundary control of incompressible Boussinesq flow. [Internet] [Masters thesis]. University of Alberta; 2016. [cited 2021 Jan 17]. Available from: https://era.library.ualberta.ca/files/cgm80hv38r.

Council of Science Editors:

Wang Z. Model order reduction and boundary control of incompressible Boussinesq flow. [Masters Thesis]. University of Alberta; 2016. Available from: https://era.library.ualberta.ca/files/cgm80hv38r

University of Michigan

20. Tang, Weihan. Reduced-Order Modeling of Mistuned Bladed Disks in Contact with Dry Friction Ring Dampers.

Degree: PhD, Mechanical Engineering, 2017, University of Michigan

URL: http://hdl.handle.net/2027.42/137043

► Bladed disks (blisks) used in turbomachinery applications frequently operate under severe forcing conditions, which can lead to high levels of dynamics responses and pre-mature high… (more)

Subjects/Keywords: Turbomachinery; Mistuning; Friction damping; Reduced-order modeling; Structural dynamics; Mechanical Engineering; Engineering

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APA (6^th Edition):

Tang, W. (2017). Reduced-Order Modeling of Mistuned Bladed Disks in Contact with Dry Friction Ring Dampers. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/137043

Chicago Manual of Style (16^th Edition):

Tang, Weihan. “Reduced-Order Modeling of Mistuned Bladed Disks in Contact with Dry Friction Ring Dampers.” 2017. Doctoral Dissertation, University of Michigan. Accessed January 17, 2021. http://hdl.handle.net/2027.42/137043.

MLA Handbook (7^th Edition):

Tang, Weihan. “Reduced-Order Modeling of Mistuned Bladed Disks in Contact with Dry Friction Ring Dampers.” 2017. Web. 17 Jan 2021.

Vancouver:

Tang W. Reduced-Order Modeling of Mistuned Bladed Disks in Contact with Dry Friction Ring Dampers. [Internet] [Doctoral dissertation]. University of Michigan; 2017. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/2027.42/137043.

Council of Science Editors:

Tang W. Reduced-Order Modeling of Mistuned Bladed Disks in Contact with Dry Friction Ring Dampers. [Doctoral Dissertation]. University of Michigan; 2017. Available from: http://hdl.handle.net/2027.42/137043

Penn State University

21. Vishwakarma, Vinod. Reduced order modeling, statistical analysis and system identification for a bladed rotor with geometric mistuning.

Degree: 2014, Penn State University

URL: https://submit-etda.libraries.psu.edu/catalog/22946

► Modified Modal Domain Analysis (MMDA) is a novel method for the development of a reduced-order model (ROM) of a bladed rotor. This method utilizes proper… (more)

▼ Modified Modal Domain Analysis (MMDA) is a novel method for the development of a reduced-order model (ROM) of a bladed rotor. This method utilizes proper orthogonal decomposition (POD) of Coordinate Measurement Machine (CMM) data of blades’ geometries and sector analyses using ANSYS. For the first time ROM of a geometrically mistuned industrial scale rotor (Transonic rotor) with large size of Finite Element (FE) model is generated using MMDA. Two methods for estimating mass and stiffness mistuning matrices are used a) exact computation from sector FE analysis, b) estimates based on POD mistuning parameters. Modal characteristics such as mistuned natural frequencies, mode shapes and forced harmonic response are obtained from ROM for various cases, and results are compared with full rotor ANSYS analysis and other ROM methods such as Subset of Nominal Modes (SNM) and Fundamental Model of Mistuning (FMM). Accuracy of MMDA ROM is demonstrated with variations in number of POD features and geometric mistuning parameters. It is shown for the aforementioned case b) that the high accuracy of ROM studied in previous work with Academic rotor does not directly translate to the Transonic rotor. Reasons for such mismatch in results are investigated and attributed to higher mistuning in Transonic rotor. Alternate solutions such as estimation of sensitivities via least squares, and interpolation of mass and stiffness matrices on manifolds are developed, and their results are discussed. Statistics such as mean and standard deviations of forced harmonic response peak amplitude are obtained from random permutations, and are shown to have similar results as those of Monte Carlo simulations. These statistics are obtained and compared for 3 degree of freedom (DOF) lumped parameter model (LPM) of rotor, Academic rotor and Transonic rotor. A state - estimator based on MMDA ROM and Kalman filter is also developed for offline or online estimation of harmonic forcing function from measurements of forced response. Forcing function is estimated for synchronous excitation of 3DOF rotor model, Academic rotor and Transonic rotor from measurement of response at few nodes. For asynchronous excitation forcing function is estimated only for 3DOF rotor model and Academic rotor from measurement of response. The impact of number of measurement locations and accuracy of ROM on the estimation of forcing function is discussed. Advisors/Committee Members: Alok Sinha, Dissertation Advisor/Co-Advisor, Christopher Rahn, Committee Member, Hosam Kadry Fathy, Committee Member, George A Lesieutre, Committee Member, Vishal Monga, Committee Member, Karen Ann Thole, Committee Member.

Subjects/Keywords: turbine; mistuning; system identification; reduced order modeling; force response; random permutation; monte carlo

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

APA (6^th Edition):

Vishwakarma, V. (2014). Reduced order modeling, statistical analysis and system identification for a bladed rotor with geometric mistuning. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/22946

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):

Vishwakarma, Vinod. “Reduced order modeling, statistical analysis and system identification for a bladed rotor with geometric mistuning.” 2014. Thesis, Penn State University. Accessed January 17, 2021. https://submit-etda.libraries.psu.edu/catalog/22946.

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

MLA Handbook (7^th Edition):

Vishwakarma, Vinod. “Reduced order modeling, statistical analysis and system identification for a bladed rotor with geometric mistuning.” 2014. Web. 17 Jan 2021.

Vancouver:

Vishwakarma V. Reduced order modeling, statistical analysis and system identification for a bladed rotor with geometric mistuning. [Internet] [Thesis]. Penn State University; 2014. [cited 2021 Jan 17]. Available from: https://submit-etda.libraries.psu.edu/catalog/22946.

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

Council of Science Editors:

Vishwakarma V. Reduced order modeling, statistical analysis and system identification for a bladed rotor with geometric mistuning. [Thesis]. Penn State University; 2014. Available from: https://submit-etda.libraries.psu.edu/catalog/22946

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

Iowa State University

22. Suram, Sunil. Strategies for including cloud-computing into an engineering modeling workflow.

Degree: 2016, Iowa State University

URL: https://lib.dr.iastate.edu/etd/15217

► With the advent of cloud computing, high-end computing, networking, and storage resources are available on-demand at a relatively low price point. Internet applications in the… (more)

▼ With the advent of cloud computing, high-end computing, networking, and storage resources are available on-demand at a relatively low price point. Internet applications in the consumer and increasingly in the enterprise space are making use of these resources to upgrade existing applications and build new ones. This is made possible by building decentralized applications that can be integrated with one another through web-enabled application programming interfaces (APIs). However, in the fields of engineering and computational science, cloud computing resources have been utilized primarily to augment existing high-performance computing hardware, but engineering model integrations still occur by the use of software libraries. In this research, a novel approach is proposed where engineering models are constructed as independent services that publish web-enabled APIs. To enable this, the engineering models are built as stateless microservices that solve a single computational problem. Composite services are then built utilizing these independent component models, much like in the consumer application space. Interactions between component models is orchestrated by a federation management system. This proposed approach is then demonstrated by disaggregating an existing monolithic model for a cookstove into a set of component models. The component models are then reintegrated and compared with the original model for computational accuracy and run-time. Additionally, a novel engineering workflow is proposed that reuses computational data by constructing reduced-order models (ROMs). This framework is evaluated empirically for a number of producers and consumers of engineering models based on computation and data synchronization aspects. The framework is also evaluated by simulating an engineering design workflow with multiple producers and consumers at various stages during the design process. Finally, concepts from the federated system of models and ROMs are combined to propose the concept of a hybrid model (information artefact). The hybrid model is a web-enabled microservice that encapsulates information from multiple engineering models at varying fidelities, and responds to queries based on the best available information. Rules for the construction of hybrid models have been proposed and evaluated in the context of engineering workflows.

Subjects/Keywords: Mechanical Engineering; Cloud-computing; Engineering workflow; Microservices; Reduced order modeling; Stateless models; Mechanical Engineering

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APA (6^th Edition):

Suram, S. (2016). Strategies for including cloud-computing into an engineering modeling workflow. (Thesis). Iowa State University. Retrieved from https://lib.dr.iastate.edu/etd/15217

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):

Suram, Sunil. “Strategies for including cloud-computing into an engineering modeling workflow.” 2016. Thesis, Iowa State University. Accessed January 17, 2021. https://lib.dr.iastate.edu/etd/15217.

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

MLA Handbook (7^th Edition):

Suram, Sunil. “Strategies for including cloud-computing into an engineering modeling workflow.” 2016. Web. 17 Jan 2021.

Vancouver:

Suram S. Strategies for including cloud-computing into an engineering modeling workflow. [Internet] [Thesis]. Iowa State University; 2016. [cited 2021 Jan 17]. Available from: https://lib.dr.iastate.edu/etd/15217.

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

Council of Science Editors:

Suram S. Strategies for including cloud-computing into an engineering modeling workflow. [Thesis]. Iowa State University; 2016. Available from: https://lib.dr.iastate.edu/etd/15217

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

University of Wisconsin – Milwaukee

23. Francis, Alex B. Experimental, Numerical and Analytical Characterization of Torsional Disk Coupling Systems.

Degree: MS, Engineering, 2014, University of Wisconsin – Milwaukee

URL: https://dc.uwm.edu/etd/625

► Torsional couplings are used to transmit power between rotating components in various power systems while allowing for small amounts of misalignment that may otherwise… (more)

Subjects/Keywords: Disc Coupling; Finite Element; Flexible Coupling; Misalignment; Reduced Order Modeling; Torsional Stiffness; Mechanical Engineering

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APA (6^th Edition):

Francis, A. B. (2014). Experimental, Numerical and Analytical Characterization of Torsional Disk Coupling Systems. (Thesis). University of Wisconsin – Milwaukee. Retrieved from https://dc.uwm.edu/etd/625

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):

Francis, Alex B. “Experimental, Numerical and Analytical Characterization of Torsional Disk Coupling Systems.” 2014. Thesis, University of Wisconsin – Milwaukee. Accessed January 17, 2021. https://dc.uwm.edu/etd/625.

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

MLA Handbook (7^th Edition):

Francis, Alex B. “Experimental, Numerical and Analytical Characterization of Torsional Disk Coupling Systems.” 2014. Web. 17 Jan 2021.

Vancouver:

Francis AB. Experimental, Numerical and Analytical Characterization of Torsional Disk Coupling Systems. [Internet] [Thesis]. University of Wisconsin – Milwaukee; 2014. [cited 2021 Jan 17]. Available from: https://dc.uwm.edu/etd/625.

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

Council of Science Editors:

Francis AB. Experimental, Numerical and Analytical Characterization of Torsional Disk Coupling Systems. [Thesis]. University of Wisconsin – Milwaukee; 2014. Available from: https://dc.uwm.edu/etd/625

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

Duke University

24. Lee, Michael William. On Improving the Predictable Accuracy of Reduced-order Models for Fluid Flows .

Degree: 2020, Duke University

URL: http://hdl.handle.net/10161/20892

► The proper orthogonal decomposition (POD) is a classic method to construct empirical, linear modal bases which are optimal in a mean L2 sense. A… (more)

Subjects/Keywords: Mechanical engineering; Fluid mechanics; Computational physics; nonlinear dynamics; proper orthogonal decomposition; reduced-order modeling; turbulence

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APA (6^th Edition):

Lee, M. W. (2020). On Improving the Predictable Accuracy of Reduced-order Models for Fluid Flows . (Thesis). Duke University. Retrieved from http://hdl.handle.net/10161/20892

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):

Lee, Michael William. “On Improving the Predictable Accuracy of Reduced-order Models for Fluid Flows .” 2020. Thesis, Duke University. Accessed January 17, 2021. http://hdl.handle.net/10161/20892.

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

MLA Handbook (7^th Edition):

Lee, Michael William. “On Improving the Predictable Accuracy of Reduced-order Models for Fluid Flows .” 2020. Web. 17 Jan 2021.

Vancouver:

Lee MW. On Improving the Predictable Accuracy of Reduced-order Models for Fluid Flows . [Internet] [Thesis]. Duke University; 2020. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/10161/20892.

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

Council of Science Editors:

Lee MW. On Improving the Predictable Accuracy of Reduced-order Models for Fluid Flows . [Thesis]. Duke University; 2020. Available from: http://hdl.handle.net/10161/20892

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

Syracuse University

25. Berger, Zachary P. The Effects of Active Flow Control on High-Speed Jet Flow Physics and Noise.

Degree: PhD, Mechanical and Aerospace Engineering, 2014, Syracuse University

URL: https://surface.syr.edu/etd/107

► The work to be presented focuses on the noise generation of a fully turbulent, compressible jet flow within a large scale anechoic chamber. The… (more)

▼ The work to be presented focuses on the noise generation of a fully turbulent, compressible jet flow within a large scale anechoic chamber. The investigations are aimed at understanding the complex nature of the jet flow field in an effort to reduce the far-field noise through active flow control and novel reduced-order modeling. The flow field of a highly subsonic, axisymmetric jet with a nozzle diameter of two inches (50.8 mm), is probed through the implementation of two-component particle image velocimetry (PIV) in the streamwise plane, along the jet's centerline. These measurements are coupled with simultaneously sampled near and far-field pressure measurements, in an effort to understand the relationship between the complex flow field in the near region of the jet and large pressure fluctuation in the far-field, responsible for the noise. In order to reduce these large pressure fluctuations in the acoustic field, it is imperative to first understand the interaction of structures in the flow field and evaluate how this relates to the propagation of acoustic signatures to the far-field. We seek to establish a low-dimensional representation of the nonlinear, turbulent flow field through the implementation of reduced-order modeling in the form of proper orthogonal decomposition. In the first set of experiments conducted, active flow control is employed in the form of synthetic jet actuation at the nozzle lip, based on previous investigations. The effects of the flow control are observed using large-window PIV and far-field pressure measurements. The results suggest that an order epsilon input elicits an order one response, with both open and closed-loop flow control. While no noise reductions are seen in the far-field as compared to the uncontrolled jet, control authority over the jet is observed. The flow control greatly enhances mixing, thus reducing the length of the potential core and causing shear layer expansion. The second set of experiments involves the implementation of a time-resolved PIV system to effectively capture the temporal evolution of the flow physics in the streamwise plane. Low-dimensional velocity modes are directly correlated to low-dimensional acoustic modes in the far-field, using the observable inferred decomposition. Preliminary findings suggest that a small subset of low-dimensional velocity modes greatly contribute to the far-field acoustics. The spatiotemporal nature of these "loud" modes are investigated in the context of potential noise-producing events. It has been found that for the Mach 0.6 uncontrolled jet, focusing on the region near the collapse of the potential core, modes 6 and 14 appear to be the loud modes, contributing significantly to the far-field noise. Further exploration of mode 6 reveals a unique interaction of structures at very specific instances in time. Thus, it is concluded that from a low-dimensional viewpoint, we have identified the deterministic spatial structures in the velocity that most highly contributes to the noise in the far-field. It is… Advisors/Committee Members: Mark N. Glauser.

Subjects/Keywords: Active Flow Control; Aeroacoustics; Jet Noise; Particle Image Velocimetry; Reduced-Order Modeling; Turbulence; Engineering

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

APA (6^th Edition):

Berger, Z. P. (2014). The Effects of Active Flow Control on High-Speed Jet Flow Physics and Noise. (Doctoral Dissertation). Syracuse University. Retrieved from https://surface.syr.edu/etd/107

Chicago Manual of Style (16^th Edition):

Berger, Zachary P. “The Effects of Active Flow Control on High-Speed Jet Flow Physics and Noise.” 2014. Doctoral Dissertation, Syracuse University. Accessed January 17, 2021. https://surface.syr.edu/etd/107.

MLA Handbook (7^th Edition):

Berger, Zachary P. “The Effects of Active Flow Control on High-Speed Jet Flow Physics and Noise.” 2014. Web. 17 Jan 2021.

Vancouver:

Berger ZP. The Effects of Active Flow Control on High-Speed Jet Flow Physics and Noise. [Internet] [Doctoral dissertation]. Syracuse University; 2014. [cited 2021 Jan 17]. Available from: https://surface.syr.edu/etd/107.

Council of Science Editors:

Berger ZP. The Effects of Active Flow Control on High-Speed Jet Flow Physics and Noise. [Doctoral Dissertation]. Syracuse University; 2014. Available from: https://surface.syr.edu/etd/107

KTH

26. Hultman, Hugo. Validation of Forced Response Methods for Turbine Blades.

Degree: Heat and Power Technology, 2015, KTH

URL: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172144

Subjects/Keywords: Forced response; Turbines; Reduced Order Modeling

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

APA (6^th Edition):

Hultman, H. (2015). Validation of Forced Response Methods for Turbine Blades. (Thesis). KTH. Retrieved from http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172144

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):

Hultman, Hugo. “Validation of Forced Response Methods for Turbine Blades.” 2015. Thesis, KTH. Accessed January 17, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172144.

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

MLA Handbook (7^th Edition):

Hultman, Hugo. “Validation of Forced Response Methods for Turbine Blades.” 2015. Web. 17 Jan 2021.

Vancouver:

Hultman H. Validation of Forced Response Methods for Turbine Blades. [Internet] [Thesis]. KTH; 2015. [cited 2021 Jan 17]. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172144.

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

Council of Science Editors:

Hultman H. Validation of Forced Response Methods for Turbine Blades. [Thesis]. KTH; 2015. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172144

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

University of Washington

27. Clark, Emily Elizabeth. Greedy algorithms for physics-informed sparse sensor selection.

Degree: PhD, 2020, University of Washington

URL: http://hdl.handle.net/1773/46548

► In this era of big data, many systems of interest to researchers are too large to fully sample. Thus, significant downsampling is necessary, but determining… (more)

▼ In this era of big data, many systems of interest to researchers are too large to fully sample. Thus, significant downsampling is necessary, but determining the best locations for optimal full-state reconstructions is an NP-hard problem. Solving for the optimal sensor selections would require the researcher to test all {n \choose p} combinations of placing p sensors given n possible locations, which is only feasible for very small systems. Instead, researchers have developed techniques to calculate near-optimal sensor placements, usually based on convex relaxations or greedy algorithms. This text focuses on a well-known greedy algorithm, the column-pivoted QR decomposition, which is performed on basis modes from a low-rank decomposition of the system, to pick out sensor locations that are approximately maximally informative and robust to noise. The column-pivoted QR decomposition is efficient and has proven optimality guarantees, but it does not account for several important practical considerations, including sensor cost, purpose, and type. In this work, we extend the QR decomposition to account for some of these real-world constraints. First, we modify the algorithm to account for a heterogeneous cost function on sensor location, selecting sensors that are approximately Pareto optimal in cost and reconstruction quality. Next, we demonstrate that the cost-constrained column-pivoted QR decomposition can be applied to modal bases beyond the most common basis of singular vectors. In this way, we can select sensors and actuators for control systems, account for a system's estimated equations of motion, and even select sensors without training data. Finally, we approach the problem of multi-fidelity sensor selection, that is, determining where and how many of each type of sensor to place, given a fixed budget and access to cheap, high-noise sensors and expensive, low-noise sensors. This problem is complex and has a very large parameter space, but we develop guidelines for asymptotic cases of sensor cost and noise level. The above methods are demonstrated on examples from physics, climate science, and facial recognition, showing that it is possible to improve sensor effectiveness and decrease cost by considering real-world practicalities. Advisors/Committee Members: Kutz, Jose N (advisor), Brunton, Steven L (advisor).

Subjects/Keywords: Control theory; Greedy algorithms; Reduced order modeling; Sensors; Physics; Applied mathematics; Mechanical engineering; Physics

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

APA (6^th Edition):

Clark, E. E. (2020). Greedy algorithms for physics-informed sparse sensor selection. (Doctoral Dissertation). University of Washington. Retrieved from http://hdl.handle.net/1773/46548

Chicago Manual of Style (16^th Edition):

Clark, Emily Elizabeth. “Greedy algorithms for physics-informed sparse sensor selection.” 2020. Doctoral Dissertation, University of Washington. Accessed January 17, 2021. http://hdl.handle.net/1773/46548.

MLA Handbook (7^th Edition):

Clark, Emily Elizabeth. “Greedy algorithms for physics-informed sparse sensor selection.” 2020. Web. 17 Jan 2021.

Vancouver:

Clark EE. Greedy algorithms for physics-informed sparse sensor selection. [Internet] [Doctoral dissertation]. University of Washington; 2020. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1773/46548.

Council of Science Editors:

Clark EE. Greedy algorithms for physics-informed sparse sensor selection. [Doctoral Dissertation]. University of Washington; 2020. Available from: http://hdl.handle.net/1773/46548

Georgia Tech

28. Limia, Alexander. Thermodynamics and thermal-fluid transport of a dual-stage sodium thermal electrochemical converter (Na-TEC).

Degree: PhD, Mechanical Engineering, 2020, Georgia Tech

URL: http://hdl.handle.net/1853/63614

► The sodium thermal electrochemical converter (Na-TEC) is a heat engine that generates electricity through the isothermal expansion of sodium ions within a β″-alumina solid-electrolyte. The… (more)

▼ The sodium thermal electrochemical converter (Na-TEC) is a heat engine that generates electricity through the isothermal expansion of sodium ions within a β″-alumina solid-electrolyte. The Na-TEC can thermodynamically achieve conversion efficiencies above 45% when operating between thermal reservoirs at 1150 K and 550 K. However, thermal management limitations have constrained previous single-stage devices to thermal efficiencies below 20%. To mitigate these limitations, the isothermal expansion can be divided into two stages: one at the evaporator temperature and another at an intermediate temperature (650 K – 1050 K). This dual-stage Na-TEC takes advantage of regeneration and reheating, and could be amenable to improved thermal management through a reduction of parasitic losses. This dissertation investigates the thermodynamic operating limits of a dual-stage Na-TEC. The dual-stage device is shown to improve the thermal efficiency by up to 7.5% points over the best performing single-stage device. An application regime map for the single- and dual-stage Na-TEC in terms of the power density and the total parasitic loss is also established. Finally, a reduced-order thermal model is used to analyze the performance of a quasi-axisymmetric dual-stage Na-TEC design with a maximum thermal efficiency of 29%. This dissertation also explores the liquid-pumping subcomponent of the Na-TEC, which consists of a capillary wick in the high-temperature evaporator used to generate the driving force. Sodium corrosion at high temperature leads to several degradation mechanisms that reduce the long-term performance of the Na-TEC. To enable low-temperature pumping solutions, a unique sodium capillary pump for the Na-TEC is explored, whereby low-pressure sodium vapor is condensed within a non-wetting stainless steel porous structure. A net force at the solid-liquid-vapor interface effectively pushes liquid sodium towards a high-pressure bulk liquid region, in contrast to traditional evaporator wicks. First, a breakthrough pressure experiment is used to measure the temperature-dependent interfacial pressure of liquid sodium on the stainless steel porous structure. These results quantify the maximum pressure that can be sustained by the interface at various temperatures, and the wetting transition temperature can be linearly extrapolated from the data. A separate experiment is then conducted to study the performance (mass flowrate vs. pressure head) of this capillary pumping mechanism. To guide the operation of this experiment, a conjugate transport model is developed to characterize sodium vapor diffusion within the porous structure. Results demonstrating the potential for liquid sodium pumping with this mechanism are discussed. Advisors/Committee Members: Yee, Shannon K. (advisor), Fedorov, Andrei G. (committee member), Lee, Seung Woo (committee member), Fuller, Thomas F. (committee member), Haynes, Comas (committee member).

Subjects/Keywords: Thermally regenerative electrochemical system; Reduced-order thermal modeling; Capillary pumping; Porous media transport

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APA (6^th Edition):

Limia, A. (2020). Thermodynamics and thermal-fluid transport of a dual-stage sodium thermal electrochemical converter (Na-TEC). (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/63614

Chicago Manual of Style (16^th Edition):

Limia, Alexander. “Thermodynamics and thermal-fluid transport of a dual-stage sodium thermal electrochemical converter (Na-TEC).” 2020. Doctoral Dissertation, Georgia Tech. Accessed January 17, 2021. http://hdl.handle.net/1853/63614.

MLA Handbook (7^th Edition):

Limia, Alexander. “Thermodynamics and thermal-fluid transport of a dual-stage sodium thermal electrochemical converter (Na-TEC).” 2020. Web. 17 Jan 2021.

Vancouver:

Limia A. Thermodynamics and thermal-fluid transport of a dual-stage sodium thermal electrochemical converter (Na-TEC). [Internet] [Doctoral dissertation]. Georgia Tech; 2020. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1853/63614.

Council of Science Editors:

Limia A. Thermodynamics and thermal-fluid transport of a dual-stage sodium thermal electrochemical converter (Na-TEC). [Doctoral Dissertation]. Georgia Tech; 2020. Available from: http://hdl.handle.net/1853/63614

University of Minnesota

29. Annoni, Jennifer. Modeling for Wind Farm Control.

Degree: PhD, Aerospace Engineering and Mechanics, 2016, University of Minnesota

URL: http://hdl.handle.net/11299/181756

► The focus of this thesis is to improve the economic viability of wind energy and help integrate wind into the electric system. Wind energy plays… (more)

Subjects/Keywords: dynamic mode decomposition; parameter varying; reduced-order modeling; system identification; wind farm control

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

APA (6^th Edition):

Annoni, J. (2016). Modeling for Wind Farm Control. (Doctoral Dissertation). University of Minnesota. Retrieved from http://hdl.handle.net/11299/181756

Chicago Manual of Style (16^th Edition):

Annoni, Jennifer. “Modeling for Wind Farm Control.” 2016. Doctoral Dissertation, University of Minnesota. Accessed January 17, 2021. http://hdl.handle.net/11299/181756.

MLA Handbook (7^th Edition):

Annoni, Jennifer. “Modeling for Wind Farm Control.” 2016. Web. 17 Jan 2021.

Vancouver:

Annoni J. Modeling for Wind Farm Control. [Internet] [Doctoral dissertation]. University of Minnesota; 2016. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/11299/181756.

Council of Science Editors:

Annoni J. Modeling for Wind Farm Control. [Doctoral Dissertation]. University of Minnesota; 2016. Available from: http://hdl.handle.net/11299/181756

Duke University

30. Balajewicz, Maciej. A New Approach to Model Order Reduction of the Navier-Stokes Equations .

Degree: 2012, Duke University

URL: http://hdl.handle.net/10161/5854

► A new method of stabilizing low-order, proper orthogonal decomposition based reduced-order models of the Navier Stokes equations is proposed. Unlike traditional approaches, this method… (more)

Subjects/Keywords: Engineering; Aerospace engineering; model reduction; Navier-Stokes; proper orthogonal decomposition; reduced order modeling; stabilization; turbulence

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

APA (6^th Edition):

Balajewicz, M. (2012). A New Approach to Model Order Reduction of the Navier-Stokes Equations . (Thesis). Duke University. Retrieved from http://hdl.handle.net/10161/5854

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):

Balajewicz, Maciej. “A New Approach to Model Order Reduction of the Navier-Stokes Equations .” 2012. Thesis, Duke University. Accessed January 17, 2021. http://hdl.handle.net/10161/5854.

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

MLA Handbook (7^th Edition):

Balajewicz, Maciej. “A New Approach to Model Order Reduction of the Navier-Stokes Equations .” 2012. Web. 17 Jan 2021.

Vancouver:

Balajewicz M. A New Approach to Model Order Reduction of the Navier-Stokes Equations . [Internet] [Thesis]. Duke University; 2012. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/10161/5854.

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

Council of Science Editors:

Balajewicz M. A New Approach to Model Order Reduction of the Navier-Stokes Equations . [Thesis]. Duke University; 2012. Available from: http://hdl.handle.net/10161/5854

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

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