Putting Research to the Test: AE Doctoral Dissertations

Each year, the Daniel Guggenheim School of Aerospace Engineering graduates between 30 and 40 doctoral students - each with unique contributions to make in research, academia, industry, and the evolution of the discipline itself. On this page, we provide links to their abstracts and their published dissertations. We're also introducing Next Gen Ideas, a video series in which our doctoral candidates will have ~ 3 minutes to explain research that took them years to produce. (No one ever said aerospace engineering was easy.) Click on the video above to get started.


2018 - 2019 Doctoral Dissertations


Sehwan OhSehwan Oh: “Reliability and Performance Tradeoffs in Conceptual Design of Hybrid Electric Aircraft Architectures (Advisor: Prof. Dimitri N. Mavris


Brett R. HillerBrett R. Hiller: "An Unsteady Aerodynamics Reduced-Order Modeling Method for Maneuvering, Flexible Flight Vehicles" (Advisor: Prof. Dimitri N. Mavris


Connie Liu:  “Investigating Physics of Nanosecond-Pulsed Argon Plasma Discharges for VLF Plasma Antenna” ( Advisor: Prof. Mitchell L.R. Walker and Prof. Morris Cohen)

Connie LiuVery low frequency (VLF) waves (3-30 kHz) are useful in communication and navigation, can deeply penetrate the ground and ocean surface, and help with satellite protection by removing energetic charged particles in the Van Allen radiation belts that damage satellite electronics. read the abstract (pdf)


Sampath Adusumilli: “Effects of Preheat Temperature and Vitiation on Reaction Kinetics of Higher Hydrocarbon Fuels”( Advisor: Prof. Jerry Seitzman

Sampath AdusumilliConducting full-scale experiments as part of the design process of jet engine combustors is a costly and time-consuming process. Therefore engine developers have been increasingly using numerical modeling approaches to assess new designs or design changes. read the abstract (pdf)


Hisham K Ali: “Magnetohydrodynamic Energy Generation and Flow Control for Planetary Entry Vehicles” (Advisors: Prof. Robert D. Braun and Prof. Mitchell L.R. Walker)

Hisham AliProposed missions such as a Mars sample return mission and a human mission to Mars require landed payload masses in excess of any previous Mars mission. Whether human or robotic, these missions present numerous engineering challenges due to their increased mass and complexity. read the abstract (pdf) | watch the video


Yixing Li: “High-Fidelity Numerical Simulation and Emulation of Bi-Fluid Swirl Injector Flow and Combustion Dynamics” (Advisor: Prof. Vigor Yang)

Yixing LiInjectors are critical components of combustion devices in liquid-fueled propulsion systems. By controlling the atomization and mixing of propellants, injectors can affect combustion efficiency, dynamic characteristics, and engine life cycle. read the abstract (pdf)


German Capuano: “Smart Finite Elements: An Application of Machine Learning To Reduced-Order Modeling Of Multi-Scale Problems” (Advisor: Julian J. Rimoli)

Tech TowerTo design structures using state-of-the-art materials like composites and metamaterials, we need predictive tools that are capable of taking into account the phenomena occurring at different length scales. However, the upscaling of nonlinear mesoscale behavior to perform system-level predictions is intractable when using conventional modeling techniques. read the abstract (pdf)


Mohit Gupta: "Enhancements in Analysis of Beam-Like Structures using Asymptotic Methods" (Advisor: Prof. Dewey Hodges)

Mohit GuptaThe state-of-the-art Variational Asymptotic Method (VAM) and a mixed formulation of Geometrically Exact Beam Theory (GEBT) are employed in this work, as a complement to conventional FEA. This framework is very fast, provides rigorous physics-based material models for composites while ensuring efficiency and accuracy. read the dissertation | what the video


Nicholas Rock: “Lean Blowout Sensitivities of Complex Liquid Fuels” (Advisor: Prof. Tim Lieuwen)

Nicholas RockLean blowout is a process whereby a previously stable flame is either extinguished or convected out of its combustor. In aviation applications, blowout is a direct threat to passenger safety and it therefore sets operational limits on a combustor. Understanding the blowout problem is a key prerequisite to the deployment of alternative aviation fuels, as these fuels are expected to have comparable flame stability characteristics as traditional jet fuels.read the abstract (pdf)


Pratibha Raghunandan: “A Numerical Study on Non-Equilibrium Multi-Temperature Thermo-Chemistry” (Advisor: Prof. Stephen Ruffin)

Pratibha RaghunandanThe accurate computation of hypersonic flowfields is an ongoing endeavor and is important for the accurate prediction of heat transfer and space vehicle design. Of the various models existing till date of varying levels of complexity, multi-temperature modeling continues to be the most widely implemented and computationally least expensive form of modeling hypersonic flows. read the dissertation


Ting Wei Chin: “Multi-Physics High Resolution Topology Optimization for Aerospace Structures” (Advisor: Prof. Graeme J. Kennedy)

Ting Wei ChinAdvancements in multimaterial additive manufacturing have the potential to enable the creation of topology optimized structures with both shape and material tailoring. These are extremely useful in creating designs for multi-physics applications where engineering experience may be lacking. read the dissertation


Younghoon ChoiYounghoon Choi: “A Framework for Concurrent Unmanned Aerial Vehicle Design and Routing for Urban Delivery Systems” (Advisor: Prof. Dimitri N. Mavris)


Yongeun Yoon: “Prediction of Limit-Cycle Oscillations in Piecewise Linear Systems” (Advisor: Prof. Eric N. Johnson)

Youngeun YoonThe mathematical model of most of mechanical and electrical systems involves the piecewise linear system, which consists of linear part and piecewise nonlinearities (PN) or sector-bounded nonlinearities such as saturation, backlash, dead-zone, etc. Many piecewise linear systems inherently possess periodic orbits called as a limit-cycle oscillation (LCO) as one of its solutions, which can seriously undermine the system performance depending on its amplitude and frequency. read the dissertation


Abhishek Mishra: “Modeling of Multistage Axial-Centrifugal Compressor Configuration using Streamtube Approach” (Advisor: Prof. J.V.R. Prasad)

Abhishek MishraQuasi-1D flow models based upon mean-line analysis are quite popular for design and performance evaluation of multistage axial and centrifugal compressors. However, they are not so readily used for analyzing the dynamic behavior of the compressor. read the abstract (pdf)


Andrea Garbo: "A Sequential Adaptive Sampling Technique Based on Local Linear Model for Computer Experiment Applications" (Advisor: Prof. Brian J. German)

Andrea GarboThe objective of this dissertation research is to develop a model independent sequential adaptive sampling technique for surrogate model (SM) applications based on a local linear model. This technique, called Nearest Neighbors Adaptive Sampling (NNAS), is conceived to be conceptually simple, computationally robust, and easy to apply, all characteristics that are crucial for effective surrogate modeling application during early phases of the engineering design process. read the dissertation


Dhwanil Shukla: “Experimental Study of Low Reynolds Number Multirotor Aerodynamic Interactions” (Advisor: Prof. Narayanan M. Komerath)

Dhwanil ShuklaIn recent years, Vertical Take-off and Landing (VTOL) rotor Unmanned Aerial Vehicles (UAVs) have gained importance in various application suited to their small size and relatively cheap construction. Among rotor UAVs, multirotor UAVs are easier to control, and hence popular. Unfortunately, the small size rotor UAVs have poor aerodynamic performance due to viscosity dominated losses and the lack of understanding of rotor-rotor and rotor-airframe interactions. read the abstract (pdf)


Chong Zhou: “Assessment of Tip Planform Effects on the  Hover Characteristics of Helicopter Rotors” (Advisor: Prof. Lakshmi N Sankar)

A distinguishing feature of helicopters compared to other flight vehicles is their reliance on the main rotor for all forces and moments needed to operate the vehicle. With the use of cyclic and collective pitch variations, pilots can readily vary and control the thrust, propulsive and side forces. Pilots can also control the vehicle attitude by tilting the rotor disk. read the dissertation


Changxi You: "Autonomous Aggressive Driving: Theory & Experiments” (Advisor: Prof. Panagiotis Tsiotras)

Autonomous vehicles represent a major trend in future intelligent transportation systems. In order to develop autonomous vehicles, this dissertation intends to understand expert driving maneuvers in different scenarios such as highway overtaking and off-road rally racing, which are referred to as ``aggressive'' driving in the context of this dissertation. By mimicking expert driving styles, one expects to be able to improve the vehicle's active safety and traffic efficiency in the development of autonomous vehicles. read the abstract (pdf)


Sayop Kim: “Advancing Turbulent Spray and Combustion Models for Compression Ignition Engine Simulations” (Advisor: Prof. Caroline L. Genzale)

Sayop KimThree-dimensional Computational Fluid Dynamics (CFD) in in-cylinder turbulent combustion is considered an integral part of engine design progress, but rather a cost-prohibitive to apply over a broad range of engine relevant conditions. In spite of successful use of existing spray atomization modeling, prior researchers have pointed out some degree of failure in low-temperature combustion (LTC) targeted injection strategies. read the dissertation


Sheng Wei: “Effect of Jet Fuel Composition on Forced Ignition in Gas Turbine Combustors” (Advisor: Prof. Jerry Seitzman)

Tech TowerThe rapid growth in the aviation industry means increasing consumption of jet fuels, which is leading to greater interest in alternate and sustainable fuel sources. The overall properties of these alternative fuels can be designed to meet existing standards. Nevertheless, the compositional differences between alternative and conventional fuels can lead to important variations in chemical and physical properties that impact engine performance. read the dissertation


Xiaomeng ‘Shine’ Zhai: "Studies of Turbulence Structure Using Well-Resolved Simulations With and Without Effects of a Magnetic Field" (Advisor: Prof. P.K. Yeung)

Xiaomeng ZhaiTurbulence is characterized by disorderly fluctuations that span a wide range of scales in length and time, especially at high Reynolds numbers. The fluctuations in the small scales can take extremely large amplitudes (also known as extreme events), and exhibit rapid oscillations in sign. read the dissertation


Raphael Cohen: "Formal Verification and Validation of Convex Optimization Algorithms for Model Predictive Control" (Advisor: Prof. Eric Feron)

Tech TowerThe efficiency of modern optimization methods, coupled with increasing computational resources, has led to the possibility of real-time optimization algorithms acting in safety critical roles. However, this cannot happen without addressing proper attention to the soundness of these algorithms. read the dissertation


Terry Stevenson: "Development of Multi-Functional Structures for Small Satellites​" (Advisor: Prof. Glenn Lightsey)

Terry StevensonImprovements in miniature electronics have allowed CubeSats and other small satellites to perform increasingly complex missions. In contrast to typical space missions, many small satellites are more limited by available volume than by mass, since they must fit into small deployment pods. read the dissertation


Adam Sidor: "Design and Manufacturing of Conformal Ablative Heatshields" (Advisor Prof. Robert Braun and Prof. Graeme Kennedy)

Adam SidorConformal ablators, first introduced in the early 2000s under the NASA Hypersonics Project, are a type of rigid ablative thermal protection system that uses flexible, rather than rigid, fibrous substrates. These materials are impregnated with resin in a mold to yield a part that is close to the final geometry and requires little post-process machining (a near net shape part).
read the abstract 
(pdf)


Kevin Jacobson: "Adjoint-based Aeroelastic Optimization with High-fidelity Time-accurate Analysis" (Advisors: Prof. Marilyn Smith and Prof. Graeme Kennedy)

Kevin JacobsonAs engineers are pursuing aggressive performance goals and exploring nontraditional aircraft configurations, the applicability of traditional aeroelastic design tools based on linear models and empirical data is diminishing. However, computer hardware and algorithms are advancing, and the use of high-fidelity tools, which utilize computational fluid dynamics and structural finite element modeling, is becoming a more realistic possibility for aircraft design. read the dissertation


Nick P. Breen: "Comparison Between Beamforming and Nearfield Contours for Source Location in Subsonic and Supersonic Jets of Various Geometries"​ (Advisor: Prof. Krishan K. Ahuja)

Nick BreenOver the years, the need to understand and reduce aircraft noise emissions has led numerous researchers to apply various source location techniques to jet noise. Prior to 1985, several methods for determining jet-noise source locations were explored: acoustic mirrors, microphone arrays, two-microphone methods, causality correlation and coherence techniques, nearfield contour surveys, and automated source breakdown. read the abstract (pdf) | watch the video


Kaivalya Bakshi: "Large Scale Stochastic Control: Algorithms, Optimality and Stability" (Advisor: Prof. Evangelos Theodorou)

Kaivalya BakshiOptimal control of large-scale multi-agent networked systems which describe social networks, macro-economies, traffic and robot swarms is a topic of interest in engineering, biophysics and economics.A central issue is constructing scalable control-theoretic frameworks when the number of agents is infinite. read the dissertation


Kyuman Lee: "Adaptive Filtering for Vision-Aided Inertial Navigation” (Advisor: Prof. Eric N. Johnson)

Kyuman LeeWith the advent of unmanned aerial vehicles (UAVs), a major area of interest in the research field of UAVs has been vision-aided inertial navigation systems (V-INS). Many missions of UAVs— reconnaissance, damage assessment, exploration, and other guidance, navigation, and control (GNC) tasks—often demand V-INS in more operational environments such as indoors, hostilities, and disasters. In V-INS, inertial measurement unit (IMU) dead reckoning generates the dynamic models of UAVs, and vision sensors extract information about the surrounding environment and determine features or points of interest. read the dissertation


Hossein Salahshoor: "Topics in Stress-Induced Instabilities and Phase Transitions in Lattice-Based Solids(Advisor: Prof. Julian J. Rimoli)

Hossein SalahshoorMechanical response of a lattice-based solid, where the entire system is built up by a repetitive translation of a unit cell along its principal axes, manifests itself in changes either in the macro or the microstructure of the system.  read the abstract (pdf)


Murali Gopal Muraleedharan: “Combustion of Nanoenergetic Materials: A Heat Conduction Perspective” (Advisor: Prof. Vigor Yang)

Murali Gopal

Metal-based composite energetic materials have substantially high volumetric energy density when compared with monomolecular compounds such as trinitrotoluene (TNT). Micron-sized metal particles have been routinely used for energetic applications since the 1950’s. read the abstract (pdf) | watch the video


Debolina Dasgupta:  “Turbulence-Chemistry Interactions for Lean Premixed Flames” (Advisor: Prof. Tim Lieuwen)

Debolina Dasgupta

Turbulent combustion, particularly premixed combustion has great practical importance due to their extensive industrial usage in gas turbines, internal combustion engines etc. However, the physics governing the inherent multi- scale interactions of turbulence, flow-field and chemistry is not yet well established.  read the dissertation | watch the video


Yu-Hung Chang: “High-Fidelity Emulation of Spatiotemporally Evolving Flow Dynamics ” (Advisor: Prof. Vigor Yang)

This dissertation utilizes a comprehensive interdisciplinary approach to demonstrate a paradigm for a novel design strategy for new generation engineering. Computational fluid dynamics (CFD), reduced-basis modeling, statistics, uncertainty quantification, and machine learning are employed to develop this strategy. read the dissertation


Burak Bagdatli: "Architecture-Based Selection of Modeling Type for System of Systems Analysis" (Advisor: Prof. Dimitri Mavris)

Burak BagdatliIntegration of heterogeneous systems into a system of systems, takes significant effort in planning, engineering, and testing. Even large entities such as governments, that are experts at managing large undertakings, are struggling with the massive complexity entailing collaboration between systems. read the dissertation