Aerospace Engineering Commons^™

Thermal Stress Analysis Of Unidirectional Composite Material By Fem Modeling, Gopal D. Gulwani

Mechanical and Aerospace Engineering Theses - Archive

Micromechanics of composite is study of complex mechanism of stress and strain transfer between fiber and matrix within a composite as well as distributions of physical fields inside heterogeneous medium. It was used successfully in predicting accurately physical properties like effective stiffness, effective linear thermal expansion of heterogeneous materials like composite. However, when it comes to strength characteristics of composite especially in transversal direction it failed to predict more accurate results. This thesis is focused on thermally induced stress analysis of unidirectional composite by finite element method. Thermal stresses which are dangerously ignored factor in mechanics of composite usually occur …

Formation Flight For Fuel Saving In Coronet Missions Of Kc-135r And F-15c/E, Christopher Allen Kniffin

Mechanical and Aerospace Engineering Theses - Archive

The fuel saving benefit of formation flight has been demonstrated through theoretical and computational analyses, simulation, wind tunnel and flight tests. When an aircraft flies in a specific region in the wake of another aircraft, it experiences upwash, which results in reduced drag and thus reduced thrust requirement. One specific USAF mission that can potentially benefit from formation flight is coronet missions. In a coronet mission, fighter aircraft are escorted and refueled, as needed, by tanker aircraft over a long range. During the flight, the receiver aircraft fly in formation with the tanker but outside of the wake of the …

Experimental Characterization And Simulation Of Carbon Nanotube Strain Sensing Films, Nagendra Krishna Chaitanya Tummalapalli

Masters Theses

Carbon Nanotubes (CNTs) have excellent mechanical, electrical and electromechanical properties. These properties led to a lot of novel applications. Due to change in electrical properties under mechanical loading, these composites have potential applications in strain sensors, when these are fabricated as films. CNT-based films are commonly fabricated using different physical and chemical techniques based on the property requirements governing those applications. In this work, CNT films were prepared using wet chemical based methods and chemical vapor deposition techniques.

Plasma chemical vapor deposition using microwave power is used in the first method to deposit films on silicon substrates, using Nickel film …

Analytical Modeling And Numerical Simulation Of A Thermoelectric Generator Including Contact Resistances, Shripad Dhoopagunta

Masters Theses

With increasing demand for energy harvesting systems, research has been conducted in different areas in which Thermoelectric Generators (TEG) find their way into the top of many available resources. Out of many energy harvesting systems available, TEGs are comparatively easier to study, to manufacture and also to comprehend while producing enough energy for applications they find use in. They are solid state devices, meaning; they do not have any moving parts and hence makes them durable. Most of the energy that goes out of the automobile as exhaust is reused to power the TEGs. In most of the works that’s …

Development Of Fault Tolerant Adaptive Control Laws For Aerospace Systems, Andres E. Perez Rocha

Doctoral Dissertations and Master's Theses

The main topic of this dissertation is the design, development and implementation of intelligent adaptive control techniques designed to maintain healthy performance of aerospace systems subjected to malfunctions, external parameter changes and/or unmodeled dynamics. The dissertation is focused on the development of novel adaptive control configurations that rely on non-linear functions that appear in the immune system of living organisms as main source of adaptation. One of the main goals of this dissertation is to demonstrate that these novel adaptive control architectures are able to improve overall performance and protect the system while reducing control effort and maintaining adequate operation …

Coupled Fluid-Structure Interaction Modeling Of A Parafoil, Brandon Burnett

Doctoral Dissertations and Master's Theses

In the summer of 2014, Performance Designs, Inc. contacted Embry-Riddle Aeronautical University’s Eagle Flight Research Center to lead an investigation on square parachute design and optimization using modern computational methods to reduce costs in experimental testing. This thesis investigates the foundation for using an implicit fluid-structure interaction computational model to tackle the challenges of modeling a highly-flexible, porous fabric for design optimization of a parafoil parachute’s transient performance. Canopy deformations of a single-cell square parafoil using a fluid-structure interaction (FSI) model with nonlinear material modeling is compared to an experimental setup of matching geometry. The results of this thesis yielded …

Model Predictive Control Of A Nonlinear Aeroelastic System Using Volterra Series Representations, Wai Leuk Law

Doctoral Dissertations and Master's Theses

The purpose of this study is to investigate the potential effectiveness of using a Volterra-based Model Predictive Control strategy to control a nonlinear aeroelastic system. Model Predictive Control (MPC), also known as Receding Horizon Control (RHC), entails computing optimal control inputs over a finite time horizon, applying a portion of the computed optimal control sequence, and then repeating the process over the next time horizon. The Volterra series provides input-output models of a dynamical system in terms of a series of integral operators of increasing order, where the first-order Volterra operator models the linear dynamics and the higher-order operators model …

Effect Of Slot Span On Wing Performance, Juan F. Granizo

Doctoral Dissertations and Master's Theses

This report presents new numerically-derived correlations to estimate the aerodynamic properties of a three-dimensional wing that features a partial to full span fixed slot. Fixed slots have been thoroughly studied in the past with regards to their operation and the relation between slot geometry and wing performance. There have also been many studies on the advantages and disadvantages of tip-slotted wings and the comparison between these and full-slotted wings. Up to this point however, a study on the effects of slot span on wing performance has not been performed. Effect of slot span on wing performance is evaluated in an …

Effect Of Flow-Acoustic Resonant Interactions On Aerodynamic Response Of Transitional Airfoils, Joseph Hayden

Doctoral Dissertations and Master's Theses

A high-accuracy numerical study is conducted to examine the impact of flow-acoustic resonant interactions on the aerodynamic response of symmetric and cambered airfoils in the realistic transitional flow regimes with Rec=140,000 and M=0.0465 as well as the low Reynolds number flow regime with Rec=10,000 and M=0.2. The symmetric NACA-0012 and the cambered SD7003 airfoils are investigated at various angles of attack that have been found previously to include both the tone and no-tone producing regimes, with specific focus on the aerodynamic lift response. Additional simulations are conducted with a low-intensity synthetic turbulence introduced upstream of the airfoils in order to …

More Electric Systems Architecture Effect On Business Jet Performance, Kelsey M. Mazur

Doctoral Dissertations and Master's Theses

A more-electric systems architecture, using current state of the art components, is proposed for the business jet Dassault Falcon 2000. A model of the existing aircraft, both of its overall flying characteristics and performance and of its detail systems layout, is created using Pacelab APDc and SysArcc programs. The model is validated with respect to the aircraft published data. Then, another model of the same aircraft is created but, this time, it is for the aircraft with the new architecture and their respective performance is compared. In particular, this results in changes in mission range and the overall system's weight. …

A Detailed Uncertainty Analysis Of Heat Transfer Experiments Using Temperature Sensitive Paint, Anish Prasad

Doctoral Dissertations and Master's Theses

Heat transfer experiments for different cooling techniques for a gas turbine blade are performed and the data are collected via temperature sensitive paint, ammeter, thermocouple and manometer measurement techniques. These data are subjected to uncertainty analysis and the major contributing parameter in the uncertainty is found. A tool to identify the major contributing parameter is devised to reduce the uncertainty in the experiment. Further the effect of temperature difference (surface temperature to bulk temperature) is studied to determine the impact on uncertainty and to determine its importance. The analysis between various implementations of the student’s t distribution are conducted to …

Configuration Validation Of A Novel In-Space Propellant Storage And Transfer System, Priyadarshan Sundararaju

Doctoral Dissertations and Master's Theses

The concept of developing a new technology for on-orbit storage and refueling system has been a great interest among scientists for many decades. This study is about Centaur-based on-orbit propellant storage and transfer. This system takes the advantage of rotational settling to a simple fluid management (FM) system. Specifically, enabling settled fluid transfer and settled pressure control between two tanks. This thesis work focuses on configuration and validation of static and dynamic stability, mass gauging and CFD analysis of the rotational propellant transfer method in space. The application of this technology in Low Earth Orbit (LEO) and Geo-Synchronous Orbit (GEO) …

Turbulence Control In Wall Jets, Jonathan Latim

Doctoral Dissertations and Master's Theses

The turbulent boundary layer has been the focus of many studies over the last century or so due to its engineering significance. Recent studies have shown that the turbulent boundary layer encapsulates extremely energetic large-scale structures which play a much more significant role in its dynamics than has been previously thought. Further, these large scales amplitude and frequency modulate the finer scales of turbulence. This offers a path to control wall turbulence by controlling the large-scales of the flow. The focus of this thesis is to establish ways to manipulate the energy of the large-scale structures in a model turbulent …

Virginia Space Pocketqube Launch Opportunity, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs titled "Virginia Space PocketQube Launch Opportunity" from December 1, 2016.

Optimization Methodology For Cvt Ratio Scheduling With Consideration Of Both Engine And Cvt Efficiency, Steven Beuerle

Masters Theses

A transmission ratio schedule is developed to optimize the fuel consumption for an automotive continuously variable transmission (CVT) connected to an internal combustion engine (ICE). Although the optimal operating line (OOL) generated from an engine brake specific fuel consumption (BSFC) map can be used to generate a CVT ratio schedule that yields maximum engine efficiency, it was found that OOL-based CVT ratio scheduling does not necessarily offer the best fuel economy because optimal CVT efficiency does not always correspond to OOL tracking. To develop a CVT ratio schedule that can offer the best fuel economy, a novel ratio-scheduling methodology is …

Modeling And Analysis Of A Novel Imbedded Organic Thermal Cycle, Joel Maker Faure

Theses and Dissertations

A thermal cycle is a device that converts thermal energy into work energy. There is a strong need in the United States and the world for a cycle that can have viable performances with low-grade temperature heat sources to increase the supply of power generation. There are many cycles with different configurations, however most do not involve mixing. Generally speaking this is due to modeling difficulties with multiple constituents, phases, and the technology available that lose performance under these mixed conditions. The gap in technology for mixed flow and phase components is getting smaller due to the need. Current cycles …

Assessing Fuel Burn Inefficiencies In Oceanic Airspace, Stephen Builta

Open Access Theses

Increasing the efficiency of aircraft operations offers a shorter term solution to decreasing aircraft fuel burn than fleet replacement. By estimating the current airspace inefficiency, we can get an idea of the upper limit of savings. Oceanic airspace presents a unique opportunity for savings due to increased separation differences vs. overland flight.

We assess fuel burn inefficiency by comparing estimated fuel burn for real world flights with the estimated optimal fuel burn. For computing fuel burn, we use the Base of Aircraft Data (BADA) with corrections based on research by Yoder (2005). Our fuel burn results show general agreement with …

Mechanism Of Shot Peening Enhancement For The Fatigue Performance Of Aa7050-T7451, Daniel James Chadwick

Open Access Theses

Shot peening is a dynamic cold working process involving the impingement of peening media onto a substrate surface. Shot peening is commonly employed as a surface treatment technique within the aerospace industry during manufacturing, in order to improve fatigue performance of structural components. The compressive residual stress induced during shot peening is understood to result in fatigue crack growth retardation, improving the performance of shot peened components. However, shot peening is a compromise between the benefit of inducing a compressive residual stress and causing detrimental surface damage. Due to the relatively soft nature of AA7050-T7451, shot peening can result in …

Flammability Limits Of Alternative Aviation Fuels, Ang Li

Open Access Theses

Alternative aviation fuels are being developed recently to partially replace the limited resources of traditional liquid fuels in the aviation industry. The fire-safety properties of these fuels, however, are unknown. Especially, the flammability limit of a fuel is a crucial parameter. The present work focuses on measurements of concentration and temperature flammability limits of four pure hydrocarbon fuels, as well as traditional and alternative aviation fuels, including Jet-A, HEFA, SIP, and FT-S8. The lower and upper concentration flammability limits of these selected fuels were determined under specific temperatures and pressures. An experiment including a customized power supply system to generate …

Characterization Of A Hypersonic Quiet Wind Tunnel Nozzle, Cameron J. Sweeney

Open Access Theses

The Boeing/AFOSR Mach-6 Quiet Tunnel at Purdue University has been able to achieve low-disturbance flows at high Reynolds numbers for approximately ten years. The flow in the nozzle was last characterized in 2010. However, researchers have noted that the performance of the nozzle has changed in the intervening years. Understand ing the tunnel characteristics is critical for the hypersonic boundary-layer transition research performed at the facility and any change in performance could have signif icant effects on research performed at the facility. Pitot probe measurements were made using Kulite and PCB pressure transducers to quantify the performance changes since characterization …

Helical Strakes On High Mast Lighting Towers And Their Effect On Vortex Shedding Lock-In, Ayah Zahour

Open Access Theses

An experimental study on the effect of helical strakes on vortex induced vibrations and the lock-in phenomenon in High Mast Lighting Towers (HMLTs) is investigated. Two multi-sided tapered scaled models are clamped in place in a subsonic wind tunnel that is equipped with a hot-wire sensor and a traverse mechanism. The shedding frequency data is collected for the models with and without helically patterned strakes with the use of two different ropes. The responses of the tower models, for a Reynolds number of 44, 000, are compared and discussed under different configurations including: two directions of the model with respect …

Metrics Of Critical Pair Identification, Zixu Zhang

Open Access Theses

Critical Pair Identification works as a potential assistive tool for human air traffic controllers by identifying potentially dangerous situations that are not detected by proposed automated separation assurance systems. This concept specifically considers conflicts that might arise if aircraft unexpectedly deviate from their planned flight path in the near future. Five metrics of the critical pair concept, Critical Pair Count, Time to Risk Exposure, Lead Time, Risk Exposure Duration and Blunder Sensitivity Index, have been developed and mathematically defined to characterize the safety level of an aircraft pair or a volume of air space. Algorithm that computes proposed metrics is …

Analysis Of Composite Plates By Using Mechanics Of Structure Genome And Comparison With Ansys, Banghua Zhao

Open Access Theses

Motivated by a recently discovered concept, Structure Genome (SG) which is defined as the smallest mathematical building block of a structure, a new approach named Mechanics of Structure Genome (MSG) to model and analyze composite plates is introduced. MSG is implemented in a general-purpose code named SwiftComp™, which provides the constitutive models needed in structural analysis by homogenization and pointwise local fields by dehomogenization. To improve the user friendliness of SwiftComp™, a simple graphic user interface (GUI) based on ANSYS Mechanical APDL platform, called ANSYS-SwiftComp GUI is developed, which provides a convenient way to create some common SG models or …

Free Edge Stress Analysis Of Laminated Structures With Arbitrary Cross Sections Using Mechanics Of Structure Genome, Lingxuan Zhou

Open Access Theses

Composite laminates have been increasingly used in advanced structural applications, due to their excellent strength-to-weight properties and considerable flexibility on designing with respect to the laminate layup. However, the heterogeneity and anisotropy of composite laminates have brought many challenges for analysis and numerous researches have been devoted in this field. A well known problem which has been studied intensively is the so-called free-edge problem. It states that due to the mismatch in elastic properties of adjacent layers, full-scale three-dimensional (3D) and highly concentrated stress fields will occur in the vicinity of the free edges. The interlaminar stresses grow very rapidly …

Modeling Methods For Merging Computational And Experimental Aerodynamic Pressure Data, Jacob Courtney Haderlie

Open Access Dissertations

This research describes a process to model surface pressure data sets as a function of wing geometry from computational and wind tunnel sources and then merge them into a single predicted value. The described merging process will enable engineers to integrate these data sets with the goal of utilizing the advantages of each data source while overcoming the limitations of both; this provides a single, combined data set to support analysis and design. The main challenge with this process is accurately representing each data source everywhere on the wing. Additionally, this effort demonstrates methods to model wind tunnel pressure data …

Gravity-Assist Trajectories To Venus, Mars, And The Ice Giants: Mission Design With Human And Robotic Applications, Kyle M. Hughes

Open Access Dissertations

Gravity-assist trajectories to Uranus and Neptune are found (with the allowance of impulsive maneuvers using chemical propulsion) for launch dates ranging from 2024 to 2038 for Uranus and 2020 to 2070 for Neptune. Solutions are found using a patched conic model with analytical ephemeris via the Satellite Tour Design Program (STOUR), originally developed at the Jet Propulsion Laboratory (JPL). Delivered payload mass is computed for all solutions for select launch vehicles, and attractive solutions are identified as those that deliver a specified amount of payload mass into orbit at the target body in minimum time. The best cases for each …

Development Of Inverse Methods For Reconstruction Of Flight Environments On Ablators, A. Brandon Oliver

Open Access Dissertations

Obtaining measurements of flight environments on ablative heatshields is both critical for spacecraft development and extremely challenging due to the harsh heating environment and surface recession. Thermocouples installed several millimeters below the surface are commonly used to measure the heatshield temperature response, but an ill-posed inverse heat conduction problem must be solved to reconstruct the surface heating environment from the embedded thermocouple measurements. The material properties of typical ablators make the reconstruction process more challenging when the measurements are deep, but measurements often must be located deep to allow for surface recession. Compounding the complexity of the surface reconstruction problem, …

A New Approach To Modeling Aviation Accidents, Arjun Harsha Rao

Open Access Dissertations

General Aviation (GA) is a catchall term for all aircraft operations in the US that are not categorized as commercial operations or military flights. GA aircraft account for almost 97% of the US civil aviation fleet. Unfortunately, GA flights have a much higher fatal accident rate than commercial operations. Recent estimates by the Federal Aviation Administration (FAA) showed that the GA fatal accident rate has remained relatively unchanged between 2010 and 2015, with 1566 fatal accidents accounting for 2650 fatalities. Several research efforts have been directed towards betters understanding the causes of GA accidents. Many of these efforts use National …

Nanostructured Morphologies In Glassy Polymer Networks, Brian Greenhoe

Dissertations

The body of this work describes a novel approach for the dispersion of multi-walled carbon nanotubes in a high T_g epoxy prepolymer matrix using a twin screw high-shear continuous reactor. The method demonstrated improves on previous dispersion methods in several ways. It offers increased efficiency through excellent heat transfer, while being solvent-less, scale-able, and tailorable to drive dispersion states to judiciously chosen dispersion states. Furthermore, it was shown that dispersion state and agglomerate morphology can be directed, in several ways, through processing conditions and also by controlling the matrix viscosity profile through cure. Broadband dielectric spectroscopy, optical hot-stage microscopy, …

Assessment Of Asymmetric Flight On Solar Uas, Eric Belfield

Master's Theses

An investigation was conducted into the feasibility of using an unconventional flight technique, asymmetric flight, to improve overall efficiency of solar aircraft. In this study, asymmetric flight is defined as steady level flight in a non-wings-level state in- tended to improve solar incidence angle. By manipulating aircraft orientation through roll angle, solar energy collection is improved but aerodynamic efficiency is worsened due to the introduction of additional trim drag. A point performance model was devel- oped to investigate the trade-off between improvement in solar energy collection and additional drag associated with asymmetric flight. A mission model with a focus on …