Engineering Commons^™

Simulation And Modeling Of Hypersonic Turbulent Boundary Layers Subject To Adverse Pressure Gradients Due To Concave Streamline Curvature, Gary L. Nicholson, Junji Huang, Lian Duan, Meelan M. Choudhari

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Direct numerical simulations (DNS) of adverse-pressure-gradient turbulent boundary layers over a planar concave wall are presented for a nominal freestream Mach number of 5, with the objective of assessing the limitations of the currently available Reynolds-averaged Navier-Stokes (RANS) models. The wall geometry and flow conditions of the DNS are representative of the experimental data for a Mach 4.9 turbulent boundary layer that was tested on a two-dimensional planar concave wall model in the high-speed blow-down wind tunnel located at the National Aerothermochemistry Laboratory at Texas A&M University (TAMU). The DNS was validated against the experimental results of TAMU for the …

Novel Adaptive Sampling Algorithm For Pod-Based Non-Intrusive Reduced Order Model, Jiachen Wang, Xiaosong Du, Joaquim R.R.A. Martins

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The proper orthogonal decomposition (POD) based reduced-order model (ROM) has been an effective tool for flow field prediction in the engineering industry. The sample selection in the design space for POD basis construction affects the ROM performance sensitively. Adaptive sampling can significantly reduce the number of samples to achieve the required model accuracy. In this work, we propose a novel adaptive sampling algorithm, called conjunction sampling strategy, which is based on proven strategies. The conjunction sampling strategy is demonstrated on airfoil flow field prediction within the transonic regime. We demonstrate the performance of the proposed strategy by running 10 trials …

Analysis Of Turbulence Model Uncertainty For Canonical Flow Problems Including Shock Wave Boundary Layer Interaction Simulations, Aaron James Erb

Doctoral Dissertations

"The purpose of this research is to present results of an uncertainty and sensitivity analysis study of commonly used turbulence models in Reynolds-Averaged Navier-Stokes (RANS) codes due to the epistemic uncertainty in closure coefficients for a set of turbulence model validation cases that represent the structure of several canonical flow problems. The study focuses on the analysis of a 2D zero pressure gradient flat plate, a 2D wall mounted hump, and an axisymmetric shock wave boundary layer interaction, all of which are well documented on the NASA Langley Research Center Turbulence Modeling Resource website. The Spalart-Allmaras (SA), the Wilcox (2006) …

Theoretical Study Of Magnetic Particles In A Shear Flow Subjected To A Uniform Magnetic Field, Christopher A. Sobecki

Doctoral Dissertations

"Magnetic manipulation of non-spherical magnetic microparticles is important for applications in shape-based and magnetic-based separations such as waste management, disease diagnostics, drug delivery, and mining. Manipulations of magnetic microparticles also include chain formation to assemble compositions for electronics, drug loading designs, and magnetorheological fluids for smart armor, hydraulic brakes, and dampers. In microfluidic devices, separation-formation-effectiveness depends on the shape of the channel, the shear rate, and the magnetic field strength and direction.

Particle separation and chain formation involved highly complex and computational expense-demanding studies in microfluidic devices, magnetic fields, and particle- particle/wall interactions. This research took complex experimental studies and …

Multi-Fidelity Modeling For Aerothermal Analysis Of Deployable Planetary Entry Technologies, Mario J. Santos

Doctoral Dissertations

“NASA is developing deployable entry technologies in the form of the Hypersonic Inflatable Aerodynamic Decelerator (HIAD) and the Adaptable Deployable Entry Technology (ADEPT) vehicles to support human exploration of Mars. To ensure that these technologies are reliable under uncertain entry conditions and extreme aerothermal environments, uncertainty quantification must be integrated into the design process which typically requires large number of high-fidelity computational fluid dynamics (CFD) simulations with prohibitively high computational cost. To address this challenge, construction of multi-fidelity aerothermal response predictions which combine low-fidelity correlations with fewer high-fidelity CFD models in a way that produces highly accurate surrogates with reduced …

Dynamic Behavior And Interactions Of Ferrofluid Droplets Under Magnetic Fields In Low Reynolds Number Flows, Md Rifat Hassan

Doctoral Dissertations

Digital microfluidics in combination with emulsion microfluidics are crucial building blocks of droplet-based microfluidics, which are prevalent in a wide variety of industrial and biomedical applications, including polymer processing, food production, drug delivery, inkjet printing, and cell-based assays. Therefore, understanding the dynamics and interactions of droplets as well as the interactions between the droplets and solid surfaces are of great importance in order to improve the performance or product in these applications.

Recently, several studies in the literature have demonstrated the potential of magnetic fields in controlling the behavior of droplets in microscale; however, the fundamental mechanism behind the interesting …

Novel Piezo Actuators For Surface Cleaning, Yezad H. Anklesaria

Doctoral Dissertations

"Optical cameras are becoming increasingly common and are used in a variety of applications. With recent progress and transition toward more autonomous systems, the usage of optical systems will be common and widespread. Applications of the optical systems range from autonomous vehicles, home security systems, aviation, extraterrestrial vehicles, spacecraft, and satellites. Imaging systems are used in decision-making in many of these applications. Fouling of the field of view of the imaging system can impede the decision process. An active autonomous cleaning method for the optical surface of the optical systems reliably would be advantageous. The research work focuses on developing …

Quantum Inspired Concepts In Decision Making, Qizi Zhang

Doctoral Dissertations

"In this study, several new applications of quantum-inspired techniques are presented to advance the state of the art in decision making. In the first part, a quantum boost scheme for multiple-model filters based on extended Grover’s algorithm is presented for fault detection and parameter estimation. The quantum boost scheme accelerates the convergence of the posterior probabilities in the multiple-model filter. Stability proofs for the quantum boost scheme is presented and its performance is analyzed using benchmark examples. In the second part, the scope of application is extended to modeling human decision making. The open quantum system cognition model is applied …

Reveal Wind Loading Of Tornadoes And Hurricanes On Civil Structures Towards Hazard-Resistant Design, Ryan Honerkamp

Doctoral Dissertations

"Extreme winds impacting civil structures lead to death and destruction in all regions of the world. Specifically, tornadoes and hurricanes impact communities with severe devastation. On average, 1200 tornadoes occur in the United States every year. Tornadoes occur predominantly in the Central and Southeastern United States, accounting for an annual $1 billion in economic losses, 1500 injuries, and 90 deaths. The Joplin, MO Tornado in 2011 killed 161 people, injured more than 1000, destroyed more than 8000 structures, and caused $2.8 billion of property loss. Hurricanes occur predominantly on the United States East coast regions and along the coast of …

Cooperative Navigation Of Small Satellites In The Deep Space Environment, Jill Christine Davis

Doctoral Dissertations

“The continued development of small satellites (SmallSats) has made them an increasingly viable mission alternative to traditional monolithic spacecraft. Constellations, swarms, and formations of these small spacecraft have the potential to fill unique gaps in the space systems architecture, while reducing overall mission costs and increasing mission redundancy. Cooperative navigation between spacecraft within swarms and formations is critical to mission success, but poses many challenges for SmallSats due to their size, mass, power, and computing constraints. While Earth orbiting missions can rely on GNSS data for high-accuracy inertial and relative navigation, deep space missions require new navigation techniques. In this …

Composite-Based Additive Manufacturing Applications In The Polymer Injection Molding Cycle, Cody Bivens

Masters Theses

“The experimental method utilized in this research was the application of composite-based additive manufacturing (CBAM) mold plates in the injection molding process. The mold plates comprised carbon fibers and polyether ether ketone (PEEK) matrix. Modifications were made to the mold plates post manufacturing in order to properly adapt to the rest of the injection molding die. A custom cooling system was engineered and integrated into the injection molding machine for the CBAM mold plates. The polymer processed in the injection molding cycle for this study was Lustran 348 acrylonitrile butadiene styrene (ABS). The result of the trials conducted in this …

Multiple-Site Fatigue Cracking Methodology To Assess Structural Integrity Of Aircraft Riveted Panels, Haroldo Chacon

Masters Theses

“Multiple Site Damage (MSD) is the most common source of Widespread Fatigue Damage (WFD) affecting structural integrity of aging aircraft fleets. Therefore, an understanding of its progression, the development of methods to prevent the onset, and the maintenance procedures precluding WFD are important to improve aircraft fleet longevity. A reliable and efficient numerical methodology to perform detailed Multiple Site Damage assessment in riveted structural joints was developed. A probabilistic methodology was employed in conjunction with Monte Carlo simulation technique; the fatigue initiation life at every potential crack initiation site was determined and initial damage scenarios were generated. Probabilistic crack growth …

Coalescence Speed Of Two Equal-Sized Nanobubbles, Eric Bird, Jun Zhou, Zhi Liang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In This Work, We Use Molecular Dynamics (MD) Simulations Coupled with Continuum-Based Theoretical Analysis to Study the Coalescence Dynamics of Two Equal-Sized Nanobubbles (NBs). We First Derive a Governing Equation for the Evolution of the Capillary Bridge Radius between Two Coalescing NBs from the Axisymmetric Navier-Stokes Equation. to Verify the Prediction from the Governing Equation, We Carry Out MD Simulations of the Coalescence of Two NBs in a Lennard-Jones Fluid System and Directly Measure the Bridge Radius, Rb, as a Function of Time, T. by Varying the Bubble Diameter, We Change the NB Ohnesorge Number from 0.46 to 0.33. in …

Efficient Yield Estimation Of Multiband Patch Antennas By Polynomial Chaos-Based Kriging, Leifur Leifsson, Xiaosong Du, Slawomir Koziel

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Yield estimation of antenna systems is important to check their robustness with respect to the uncertain sources. Since direct Monte Carlo sampling of accurate physics-based models can be computationally intensive, this work proposes the use of the polynomial chaos–Kriging (PC-Kriging) metamodeling method for fast yield estimation of multiband patch antennas. PC-Kriging integrates the polynomial chaos expansion (PCE) as the trend function of Kriging metamodel since the PCE is good at capturing the function tendency and Kriging is good at matching the observations at training points. The PC-Kriging method is demonstrated on two analytical cases and two multiband patch antenna cases …

Maximum Evaporating Flux Of Molecular Fluids From A Planar Liquid Surface, Eric Bird, Zhi Liang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In This Work, We Use the Kinetic Theory of Gases (KTG) to Develop a Theoretical Model to Understand the Role of Internal Motions of Molecules on the Maximum Evaporation Flux from a Planar Liquid Surface. the Kinetic Theory is Applied to Study the Evaporation of Molecular Fluids into a Vacuum and Predict the Dimensionless Maximum Evaporation Flux (JR,max, I.e., the Ratio of the Maximum Evaporation Flux to the Molar Flux Emitted from a Liquid Surface). the Key Assumptions Regarding the Velocity Distribution Function (VDF) of Polyatomic Molecules in the Highly Nonequilibrium Vapor Near the Evaporating Surface Are Validated by the …

Application Of Quantum-Markov Open System Models To Human Cognition And Decision, Jerome Busemeyer, Qizi Zhang, S. N. Balakrishnan, Zheng Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Markov processes, such as random walk models, have been successfully used by cognitive and neural scientists to model human choice behavior and decision time for over 50 years. Recently, quantum walk models have been introduced as an alternative way to model the dynamics of human choice and confidence across time. Empirical evidence points to the need for both types of processes, and open system models provide a way to incorporate them both into a single process. However, some of the constraints required by open system models present challenges for achieving this goal. The purpose of this article is to address …

Thermal Transport Across The Interface Between Liquid N-Dodecane And Its Own Vapor: A Molecular Dynamics Study, Eric Bird, Jesus Gutierrez Plascencia, Zhi Liang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

There Are Two Possible Thermal Transport Mechanisms at Liquid-Gas Interfaces, Namely, Evaporation/condensation (I.e., Heat Transfer by Liquid-Vapor Phase Change at Liquid Surfaces) and Heat Conduction (I.e., Heat Exchange by Collisions between Gas Molecules and Liquid Surfaces). using Molecular Dynamics (MD) Simulations, We Study Thermal Transport Across the Liquid-Vapor Interface of a Model N-Dodecane (C12H26) under Various Driving Force Conditions. in Each MD Simulation, We Restrict the Thermal Energy to Be Transferred Across the Liquid-Vapor Interface by Only One Mechanism. in Spite of the Complex Intramolecular Interactions in N-Dodecane Molecules, Our Modeling Results Indicate that the Schrage Relationships, Which Were Shown …

A Molecular Dynamics Study Of Transient Evaporation And Condensation, Zhi Liang, Anirban Chandra, Eric Bird, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We Use Molecular Dynamics (MD) Simulations to Study the Transient Evaporation and Condensation of a Pure Fluid Ar in a Nanochannel. in the MD Model, the Evaporation and Condensation of Fluid Ar is Initiated by a Sudden Increase of the Temperature or Periodically Varying the Temperature in the Solid Substrate on One Side of the Nanochannel. in Both Cases, We Find the Transient Evaporation and Condensation Rates Obtained Directly from MD Simulations Are in Good Agreement with the Predictions from the Schrage Relationships. Furthermore, Our Analyses Show that the Kinetics of the Transient Heat and Mass Transfer between the Evaporating …

Multifidelity Modeling By Polynomial Chaos-Based Cokriging To Enable Efficient Model-Based Reliability Analysis Of Ndt Systems, Xiaosong Du, Leifur Leifsson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This work proposes a novel multifidelity metamodeling approach, the polynomial chaos-based Cokriging (PC-Cokriging). The proposed approach is used for fast uncertainty propagation in a reliability analysis of nondestructive testing systems using model-assisted probability of detection (MAPOD). In particular, PC-Cokriging is a multivariate version of polynomial chaos-based Kriging (PC-Kriging), which aims at combining the advantages of the regression-based polynomial chaos expansions and the interpolation-based Kriging metamodeling methods. Following a similar process as Cokriging, the PC-Cokriging advances PC-Kriging by enabling the incorporation of multifidelity physics information. The proposed PC-Cokriging is demonstrated on two analytical functions and three ultrasonic testing MAPOD cases. The …

Comparison Of Reynolds-Averaged Navier-Stokes Turbulence Models For Simulating Boundary Layers In Hypersonic Flows, Jorge-Valentino Kurose Bretzke

Masters Theses

“This study describes the use of Computational Fluid Dynamics (CFD) codes to simulate hypersonic boundary layers using several different turbulent closure models and comparing Reynolds-Averaged Navier-Stokes (RANS) simulations against Direct Numerical Simulations (DNS) of similar test cases. The test cases in this study consist of a flat plate in a Mach 8 freestream with a zero pressure gradient and wall recovery ratio of 0.48, as well as a Mach 8 axisymmetric nozzle also with a cold wall. The RANS models used in this study are the Spalart-Allmaras model, Baldwin-Lomax model, Menter K-Omega Baseline and Menter K-Omega Shear Stress Transport models. …

Direct Numerical Simulations Of Acoustic Disturbances In Various Rectangular Nozzle Configurations, Nathaniel Hildebrand, Meelan M. Choudhari, Lian Duan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We perform Direct Numerical Simulations (DNS) to study the acoustic freestream disturbances radiating from the turbulent boundary layers along the contoured nozzle walls of a hypersonic wind tunnel with a rectangular test section. To begin with, the effects of the spanwise end walls are suppressed by confining the spanwise computational domain to a finite segment of the overall nozzle cross section and by imposing periodic boundary conditions across that spanwise domain. Besides providing a building-block configuration to reveal partial effects of the enclosed acoustic environment within the wind tunnel, these computations serve as a steppingstone toward the goal of fully-3D …

Direct Numerical Simulation Of Turbulent Pressure Fluctuations Over A Cone At Mach 8, Junji Huang, Lian Duan, Katya M. Casper, Ross M. Wagnild, Neal P. Bitter

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Direct numerical simulations (DNS) were conducted to characterize the pressure fluctuations under the turbulent portion of the boundary layer over a sharp 7◦ half-angle cone at a nominal freestream Mach number of 8 and a unit Reynolds number of Reunit = 13.4 x 106/m. The axisymmetric cone geometry and the flow conditions of the DNS matched those measured in the Sandia Hypersonic Wind Tunnel at Mach 8 (Sandia HWT-8). The DNS-predicted wall pressure statistics, including the root-mean-square (r.m.s.) fluctuations and the power spectral density (PSD), were compared with those measured in the Sandia HWT-8. A good comparison between the DNS …

Simulation And Modeling Of Cold-Wall Hypersonic Turbulent Boundary Layers On Flat Plate, Junji Huang, Gary L. Nicholson, Lian Duan, Meelan M. Choudhari, Rodney D.W. Bowersox

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Direct numerical simulations (DNS) of flat-plate, zero-pressure-gradient turbulent boundary layers are presented for nominal freestream Mach numbers of 11 and 14 and a highly cooled wall (wall-to-recovery temperature of approximately 0.2). The flow conditions of the DNS are representative of the experimental data for a Mach 11.1 turbulent boundary layer on a flat plate that was tested at Calspan–University of Buffalo Research Center (CUBRC) and the operational conditions of the AEDC Hypervelocity Tunnel No. 9 at Mach 14. The wall shear stress and turbulent heat flux predicted by DNS show good comparisons with those measured at CUBRC and those modeled …

Numerical Study Of Paramagnetic Elliptical Microparticles In Curved Channels And Uniform Magnetic Fields, Christopher Sobecki, Jie Zhang, Cheng Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We numerically investigated the dynamics of a paramagnetic elliptical particle immersed in a low Reynolds number Poiseuille flow in a curved channel and under a uniform magnetic field by direct numerical simulation. A finite element method, based on an arbitrary Lagrangian-Eulerian approach, analyzed how the channel geometry, the strength and direction of the magnetic field, and the particle shape affected the rotation and radial migration of the particle. The net radial migration of the particle was analyzed after executing a π rotation and at the exit of the curved channel with and without a magnetic field. In the absence of …

A Brief Review On 3d Bioprinted Skin Substitutes, Fateme Fayyazbakhsh, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Global Escalating Cases of Skin Donor Shortage for Patients with Severe Wounds Warn the Vital Need for Alternatives to Skin Allografts. over the Last Three Decades, Research in the Skin Regeneration Area Has Addressed the Unmet Need for Artificial Skin Substitutes. 3D Bioprinting is a Promising Innovative Technology to Accurately Fabricate Skin Constructs based on Natural or Synthetic Bioinks, Whether Loaded or Not Loaded with Native Skin Cells (I.e., Keratinocytes and Fibroblasts) or Stem Cells in the Prescribed 3D Hierarchal Structure to Create Artificial Multilayer and Single Cell-Laden Construct. in This Paper, the Recent Developments in 3D Bioprinting for …

A B-Spline-Based Generative Adversarial Network Model For Fast Interactive Airfoil Aerodynamic Optimization, Xiaosong Du, Ping He, Joaquim R.R.A. Martins

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Airfoil aerodynamic optimization is of great importance in aircraft design; however, it relies on high-fidelity physics-based models that are computationally expensive to evaluate. In this work, we provide a methodology to reduce the computational cost for airfoil aerodynamic optimization. Firstly, we develop a B-spline based generative adversarial networks (BSplineGAN) parameterization method to automatically infer design space with sufficient shape variability. Secondly, we construct multi-layer neural network (MNN) surrogates for fast predictions on aerodynamic drag, lift, and pitching moment coefficients. The BSplineGAN has a relative error lower than 1% when fitting to UIUC database. Verification of MNN surrogates shows the root …

Applications Of Polynomial Chaos-Based Cokriging To Aerodynamic Design Optimization Benchmark Problems, Jethro Nagawkar, Leifur Leifsson, Xiaosong Du

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this work, the polynomial chaos-based Cokriging (PC-Cokriging) is applied to a benchmark aerodynamic design optimization problem. The aim is to perform fast design optimization using this multifidelity metamodel. Multifidelity metamodels use information at multiple levels of fidelity to make accurate and fast predictions. Higher amount of lower fidelity data can provide important information on the trends to a limited amount of high-fidelity (HF) data. The PC-Cokriging metamodel is a multivariate version of the polynomial chaos-based Kriging (PC-Kriging) metamodel and its construction is similar to Cokriging. It combines the advantages of the interpolation-based Kriging metamodel and the regression-based polynomial chaos …

Effect Of Turbulence Model Closure Coefficient Uncertainty On Scramjet Flow Field Analysis, Martin Albert Di Stefano

Doctoral Dissertations

“The numerical modeling of supersonic combustion ramjet (scramjet) engine flow paths plays an important role in the design of hypersonic air-breathing propulsion systems. Due to the complexity of the flow field physics and limited experimental data, numerical models possess uncertainties which should be addressed to improve the prediction accuracy of the simulations. In this study, the effect of turbulence model closure coefficient uncertainty on the Reynolds-averaged Navier-Stokes solution of a scramjet isolator and scramjet strut fuel injector flow field is investigated with an uncertainty quantification and sensitivity analysis study for commonly used turbulence models. Turbulence models considered in this work …

Experimental Investigation Of Ionic Liquid Mixtures For Electrospray Propulsion, Mitchell J. Wainwright

Doctoral Dissertations

"In recent years, there has been a dramatic increase in the number of small satellites (namely MicroSats, NanoSats, and CubeSats) in earth orbit; many of these are launched without propulsion systems. Multi-mode propulsion systems, capable of operating in either chemical or electric mode, have been proposed as attractive candidates for use in small satellites. Such systems are mass and volume optimal and flexible in terms of thrust requirements. Most previous work on multi-mode systems has focused on chemical mode performance.The work in this dissertation focuses on the electric mode performance of these propulsion systems.

The work in this research is …

Fabrication And Characterization Of Multifunctional Composites, Aditya R. Thakur

Doctoral Dissertations

“This study details the research to facilitate fabrication and characterization of novel structural composites reinforced with carbon fibers. Across industries, materials with high performance-to-weight ratio are sought after. Using carbon fibers as secondary phases in these proposed composites, specific characteristics can be tailored in these materials to manufacture strong, lightweight, high performance structures. The first part of the research focused on the improvement in the mechanical properties of the composites using carbon fiber reinforcement. As a part of this study, toughened ceramic composites with predictable failure patterns were produced using carbon fiber inclusions. A closed-form analytical model was developed to …