Aerospace Engineering Commons^™

Generation Of Premix Laminar Flame Speed Library, Sai Prashanth Kumar

Dissertations, Master's Theses and Master's Reports

The Laminar flame speed is an essential parameter in measuring turbulent premixed combustion applied in Spark ignition engines. Instead of using power-law correlations, which is valid only for particular ranges, the procedure for generating a premixed laminar flame speed library is defined using MTU – Master mechanism for a wide range of charge mixture conditions inside an engine combustion chamber: Temperature (300 – 700 K), Pressure (1 – 70 bar) and reactant mixture composition of equivalence ratio (0.4 – 2.0) Laminar flame speed library is generated for methane. The mechanism's performance was improved by adjusting the pre-exponential factor of the …

Generalization Of Polynomial Chaos For Estimation Of Angular Random Variables, Christine Louise Schmid

Doctoral Dissertations

“The state of a dynamical system will rarely be known perfectly, requiring the variable elements in the state to become random variables. More accurate estimation of the uncertainty in the random variable results in a better understanding of how the random variable will behave at future points in time. Many methods exist for representing a random variable within a system including a polynomial chaos expansion (PCE), which expresses a random variable as a linear combination of basis polynomials.

Polynomial chaos expansions have been studied at length for the joint estimation of states that are purely translational (i.e. described in Cartesian …

Applications Of Information Theory In Filtering And Sensor Management, Matthew James Gualdoni

Doctoral Dissertations

“A classical sensor tasking methodology is analyzed in the context of generating sensor schedules for monitoring resident space objects (RSOs). This approach, namely maximizing the expected Kullback-Leibler divergence in a measurement update, is evaluated from a probabilistic perspective to determine the accuracy of the conventional approach. In this investigation, a newdivergence-based approach is proposed to circumvent themyopic nature of the measure, forecasting the potential information contribution to a time of interest and leveraging the system dynamics and measurement model to do so. The forecasted objective exploits properties of a batch measurement update to frequently exhibit faster optimization times when compared …

Forming And Processing Of Advanced Fiber Reinforced Polymer Composites, Robert Meinders

Doctoral Dissertations

“Composite materials are commonly used in industry to manufacture strong and lightweight structures. Composites feature a large degree of flexibility in materials selection and manufacturing processes to tailor the strength of manufactured parts. This study examines different manufacturing aspects of composites. In Part I, the fabrication of composite parts using the compression forming process is examined. During compression forming, metal dies are used to apply large deformations to prepreg material to fabricate composite parts. The high stresses and deformations of this process can yield manufacturing defects. T650/5320-1 prepreg is subjected to material characterization to develop simulations of large deformation forming …

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 …

Finite Time Suboptimal Control Design Of Nonlinear Systems With Θ-D Technique And Implementation To Aerospace Applications, Jie Yao

Doctoral Dissertations

“A finite time suboptimal control strategy (named θ - D approximated algorithm) was proposed in this study, which can provide the control engineers with a novel effective and efficient design tool from the finite time optimal perspective. Based on the framework of this proposed method, the original nonlinear dynamics were formulated in pseudo-linear form, and the performance index was denoted by a linear quadratic regulator prototype in this research. After that, the approximated solutions to intractable Hamilton-Jacobi-Bellman (HJB) equation were acquired by putting vanishing perturbation terms into the performance index. By tuning the parameters in perturbation terms, semi-global stability and …

A Cfd Study Investigating Drag Reduction For Different Offset And Inline Distance For Two Trucks Platooning, Wael Mokhtar, Kyle Dinger, Shardul Kachare, Mdrazib Hossain, Colin Britcher

Mechanical & Aerospace Engineering Faculty Publications

The automotive industry invests huge resources to improve fuel consumption of commercial vehicles by improving their aerodynamic efficiency. Recently, numerous studies investigating the effect of platooning on aerodynamic drag of semi-trucks have been performed by researchers indicating a positive impact. For the present study, a three-dimensional computational study was performed to investigate the effect of varying offset and linear distance during platooning on the total drag of two semi-trucks. The study was conducted on a full-scale model using Reynold’s Averaged Navier-Strokes governing equations for a moving ground simulation using the STAR-CCM+ computational package. Furthermore, for turbulence, the standard k- …

Reliable Navigation For Suas In Complex Indoor Environments, Andrew J. Fabian

Theses and Dissertations

Indoor environments are a particular challenge for Unmanned Aerial Vehicles (UAVs). Effective navigation through these GPS-denied environments require alternative localization systems, as well as methods of sensing and avoiding obstacles while remaining on-task. Additionally, the relatively small clearances and human presence characteristic of indoor spaces necessitates a higher level of precision and adaptability than is common in traditional UAV flight planning and execution. This research blends the optimization of individual technologies, such as state estimation and environmental sensing, with system integration and high-level operational planning.

The combination of AprilTag visual markers, multi-camera Visual Odometry, and IMU data can be used …

The Use Of Polyvinyldene Fluoride (Pvdf) Films For Pressure Measurement, Patrick Smith

Summer Community of Scholars Posters (RCEU and HCR Combined Programs)

No abstract provided.

Unsteady Aerodynamic Analysis Of Wind Harvesting Aircraft, Judd Mehr, Eduardo Alvarez, Andrew Ning

Faculty Publications

Airborne Wind Energy (AWE) technology aspires to provide increased options for wind energy harvesting. This includes increased feasibility for temporary and remote installations, as well as the ability to operate at wind speeds both lower and higher than traditional turbines. Additionally, the hope is to be able to produce these extensions of wind energy technology at a lower cost than conventional technologies. As AWE technology is still in its infancy, however, there is very little published information concerning the aerodynamic details of the technology. We have created a set of aerodynamic analysis tools which we apply to wind harvesting aircraft, …

Efficiency Of Gas Turbine Engines, Tahir A. Upshaw

The Kennesaw Journal of Undergraduate Research

The following research involves conducting a confirmation of test bench results, and parametric cycle analysis. The results from these two methods of data collection is meant to show relationship between both. Where the data of the price induction can be verified with the parametric cycle analysis of the individual components to calculate the thrust and efficiency. Once we compare both methods, it will allow us to move on to part two of the research which involves determining how to make gas turbine engines more efficient based on the collected data.

Design And Development Of Power Processing Units For Applications In Electrically-Propelled Satellite Systems, Kartikeya Jayadurga Prasad Veeramraju

Masters Theses

"Electrospray technology provides a way to ionize specialized liquids by applying high voltages across a sharp porous tip and a metallic mesh. This technology is widely used in the field of mass spectroscopy for generating ions for testing purposes. The dawn of nano-satellites posed new challenges in the miniaturization of many conventional satellite sub-systems. One significant challenge faced in such a process was the miniaturization of the propulsion system. Electrosprays have started to find their application in the field of Aerospace Engineering and now are formally known as Electrospray Thrusters. These thrusters provide high specific impulse and are attractive substitutes …

Assessment And Applications Of The Conversion Of Chemical Energy To Mechanical Energy Using Model Rocket Engines, Hüseyin Sarper, Nebojsa I. Jaksic, Ben J. Stuart, Karina Arcaute

Mechanical & Aerospace Engineering Faculty Publications

To provide the first-year engineering students with a hands-on experience in an engineering application using both chemistry and physics, this team project uses a set of chemical and physical energy concepts and MS Excel based analysis. The main objective of the project is to calculate how much of the potential maximum possible chemical energy is converted into propulsion when using model rocket engines with solid fuel. The secondary objective is to determine the effects of increasing conversion rates on the performance of a model rocket. The solid fuel or propellant used in common model rocket engines is black powder. Compared …

Ensuring Positive Definiteness In Linear Viscoelastic Material Functions Based On Prony Series, Christopher D. Rehberg

Honors Undergraduate Theses

This thesis presents a method to correct for non-positive-definiteness in linear viscoelastic material functions. Viscoelastic material functions for anisotropic materials need to be interconverted in a matrix coefficient prony series form, with a requirement of positive definiteness. Fitting is usually done as a uniaxial prony series, resulting in scalar coefficients. When these uniaxial coefficients are placed in a coefficient matrix, the required positive definiteness cannot be guaranteed. For those matrices that do not meet this requirement, finding the nearest symmetric semi-positive definite form of the matrix results in a viable prony series matrix coefficient with the required positive definiteness. These …

Degradation From Cmas Infiltration In 7ysz Eb-Pvd Thermal Barrier Coatings, Zachary Stein

Honors Undergraduate Theses

The lifetime of the high temperature ceramic coating 7 wt.% yttria-stabilized zirconia (7YSZ) is reduced when calcium-magnesium-alumino-silicate (CMAS) particulates enters aero-engines during operation in a sandy or dusty environment, melts, and infiltrates into the coating. 7YSZ undergo both chemical and mechanical degradation from CMAS infiltration during cycling. Characterization methods with synchrotron X-ray diffraction (XRD) provides a non-destructive means to measure the impact of time and temperature on coating degradation with high spatial resolution of 7YSZ coatings infiltrated and annealed by CMAS for 1 hour and 10 hours as well as at 1225 °C and 1250 °C. Additionally, qualitative results of …

Development Of A Computationally Inexpensive Method Of Simulating Primary Droplet Breakup, Brendon A. Cavainolo

Honors Undergraduate Theses

Liquid droplet impingement on aircraft can be problematic as it leads to ice accretion. There have been many incidents of aircraft disasters involving ice accretion, such as American Eagle Flight 4184. Understanding liquid droplet impingement is critical in designing aircraft that can mitigate the damages caused by icing. However, the FAA's regulations are only specified for "Appendix C" droplets; thus, aircraft designs may not be safe when accounting for droplets such as Supercooled Large Droplets. The assumptions of many models, such as the Taylor-Analogy Breakup (TAB) model, are no longer accurate for Supercooled Large Droplets, and the physics of those …

Evaluation Of Convective Heat Transfer Numerical Methods On Rough Surfaces From Additive Manufacturing, Jose Urcia

Electronic Theses and Dissertations, 2020-2023

The high versatility of additive manufacturing has led to an increase in use in a number of different fields. Surface roughness then comes as a natural consequence of additive manufacturing which interferes with a smooth wall assumption such as those found in gas turbine blades. The Discrete Element Roughness Method (DERM) has been used to improve convective heat transfer predictions on surface roughness. This work aims to validate the core momentum and heat transfer correlation of DERM through an evaluation of Computational fluid dynamics (CFD)-based solution of the flow around individual roughness elements with the goal of improving the correlations. …

Atv Dynamics And Pediatric Rider Safety, James T. Auxier Ii

Theses and Dissertations--Biomedical Engineering

It has been observed through numerous academic and governmental agency studies that pediatric all-terrain vehicle ridership carries significant risk of injury and death. While no doubt valuable to safety, the post-hoc approach employed in these studies does little to explain the why and how behind the risk factors. Furthermore, there has been no prolonged, widespread, organized, and concerted effort to reconstruct and catalog the details and causes of the large (20,000+) number of ATV-related injuries that occur each year as has been done for road-based motor vehicle accidents. This dissertation takes the opposite approach from a meta-analysis and instead examines …

Influence Of Size Effects On Surface Generation During Finish Machining And Surface Integrity In Ti-6al-4v, Ian S. Brown

Theses and Dissertations--Mechanical and Aerospace Engineering

Finish machining is an essential manufacturing process that is used to enhance the mechanical characteristics of critical components. The deformation that occurs at the tool and workpiece interface in finish machining significantly affects a host of component properties, commonly referred to as “surface integrity” properties. Surface roughness is a machining deformation-affected characteristic that is of high relevance in contemporary manufacturing. However, over recent decades it has been made clear that the material properties of the deformed surface layers are relevant to component performance as well. Predicting the overall surface quality of a machined component is of great relevance to the …

Flame Stabilization Of A Premixed Jet In Vitiated Coflow, Tyler Owens

Theses and Dissertations--Mechanical and Aerospace Engineering

Premixed staged combustion in gas turbine engines can reduce emissions by lowering peak flame temperatures but can also lead to different stability characteristics when compared to traditional combustors. High pressure ratio and subsequently high temperatures can lead to conditions suitable for both autoignition and premixed flame propagation in an environment where spatial fuel/air variations are present.

An experimental facility which issues a premixed jet into a coflowing vitiated mixture was studied to examine the stability behavior, resulting in a lifted flame. The effective ignition delay observed flame was much greater than homogeneous ignition delay calculations for the same conditions. It …

Development Of Universal Solver For High Enthalpy Flows Through Ablative Materials, Umran Duzel

Theses and Dissertations--Mechanical and Aerospace Engineering

Atmospheric entry occurs at very high speeds which produces high temperature around the vehicle. Entry vehicles are thus equipped with Thermal Protection Systems which are usually made of ablative materials. This dissertation presents a new solver that models the atmospheric entry environment and the thermal protection systems. In this approach, both the external flow and the porous heat shield are solved using the same computational domain. The new solver uses the Volume Averaged Navier-Stokes Equations adapted for hypersonic non-equilibrium flow, and is thus valid for both domains. The code is verified using analytical problems, set of benchmarks and also a …

Carbon Oxidation At The Atomic Level: A Computational Study On Oxidative Graphene Etching And Pitting Of Graphitic Carbon Surfaces, Simon Schmitt

Theses and Dissertations--Mechanical and Aerospace Engineering

In order to understand the oxidation of solid carbon materials by oxygen-containing gases, carbon oxidation has to be studied on the atomic level where the surface reactions occur. Graphene and graphite are etched by oxygen to form characteristic pits that are scattered across the material surface, and pitting in turn leads to microstructural changes that determine the macroscopic oxidation behavior. While this is a well-documented phenomenon, it is heretofore poorly understood due to the notorious difficulty of experiments and a lack of comprehensive computational studies. The main objective of the present work is the development of a computational framework from …

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 …

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 …

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 …

Erratum: Minimization Of The Kullback-Leibler Divergence For Nonlinear Estimation (Journal Of Guidance, Control, And Dynamics, (2017), 10.2514/1.G002282), Jacob E. Darling, Kyle J. Demars

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Erratum Notice In the original article [https://doi.org/10.2514/1.G002282], Eqs. (16b) and (18b) were typeset as (Formula Presented) which incorrectly show that the posterior covariance at time tk, denoted by Pk, is calculated about the prior mean, m−k. The correct forms of these equations are given by (Formula Presented) which show that Pk is calculated about the posterior mean, mk. All resulting analyses and simulations reported in the article were performed using the correct forms of the equations.

Impartial Sensor Tasking Via Forecasted Information Content Quantification, Matthew J. Gualdoni, Kyle J. Demars

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The consistently increasing population of space debris in orbit about the Earth is becoming an increasingly unavoidable problem, necessitating a proper handling of the problem of sensor tasking to effectively and efficiently obtain observations of space objects to maintain catalogs of their positions and velocities. A variety of approaches have been explored to achieve this in an autonomous fashion, assisting with space traffic management. This work presents new statistical analysis of the Kullback–Leibler divergence justifying the use of its expected value in generating sensor schedules. This divergence's use as an objective measure is extended to simultaneously consider, in an impartial …

Information-Based Particle Flow For High Uncertainty Estimation, Kari C. Ward, Kyle J. Demars

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This work presents a new formulation of the Gaussian particle flow filter derived using an information theoretic approach. The developed information flow addresses two problems with Gaussian particle flow: the lack of inherent meaning in the flow parameters and the inability to easily include modifications for a non-Bayesian update. Equivalency between Gaussian particle flow and information flow is established using a linear, Gaussian example. An orbit determination simulation with high initial uncertainty is used to demonstrate the consistent, robust performance of the information flow filter in situations where the extended Kalman filter fails.

Propagation Of Errors Through Coning, Sculling, And Scrolling Correction Algorithms, James D. Brouk, Kyle J. Demars

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper investigates the propagation of estimation errors through a common coning, sculling, and scrolling architecture used in modern day inertial navigation systems. Coning, sculling, and scrolling corrections often have an unaccounted-for effect on the error statistics of inertial measurements used to describe the state and uncertainty propagation for position, velocity, and attitude estimates. Through the development of an error analysis for a set of coning, sculling, and scrolling algorithms, mappings of the measurement and estimation errors through the correction term are adaptively generated. Using the developed mappings, an efficient and consistent propagation of the state and uncertainty, within the …

Optimization Strategies For Myopic And Forecasted Divergence-Based Sensor Tasking Objectives, Matthew J. Gualdoni, Kyle J. Demars

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In light of the ever-increasing value of space assets operating in the presence of a continuously growing population of space objects in orbit about Earth, space situational awareness is becoming more crucial than ever. The process of tracking and maintaining estimates for the numerous assets and space objects is a complex and highly demanding problem, as it requires robust state estimates in the presence of sparse data. As the number of space objects greatly outweighs the number of available sensors, a sensor tasking policy is necessary to properly utilize the available sensor resources in a way that ensures targets are …