Aerospace Engineering Commons^™

Dynamic Aeroelastic Analysis Of Wing/Store Configurations, Gregory H. Parker

Theses and Dissertations

Limit-cycle oscillation, or LCO, is an aeroelastic phenomenon characterized by limited amplitude, self-sustaining oscillations produced by fluid-structure interactions. In order to study this phenomenon, code was developed to interface a modal structural model with a commercial computational fluid dynamics program. LCO was simulated for a rectangular wing, referred to as the Goland⁺ wing. It was determined that the aerodynamic nonlinearity responsible for LCO in the Goland+ wing was the combination of strong trailing-edge and lambda shocks which periodically appear and disappear. This mechanism limited the flow of energy into the structure which quenched the growth of the flutter, resulting …

An Automated Optimal Design Of A Fan Blade Using An Integrated Cfd/Mdo Computer Environment, Uyi O. Idahosa

Master's Theses - Daytona Beach

The objective of the investigation is the development of more efficient design methodologies based on the applications of established design tools including Computational Fluid Dynamics (CFD) and non-linear Multidisciplinary Design Optimization (MDO) algorithms. Well known evolutionary type optimization algorithms include the Particle Swarm Optimization (PSO), Response Surface Optimization (RSO) and Genetic (GA) Algorithms. The benchmark case study is the optimal design of a low speed fan for an industrial air-conditioning application using the Response Surface Optimization (RSO) algorithm.

The optimization algorithm controls the variations of parameters that describe the three-dimensional geometry of the blade while applying performance and geometrical constraints …

Approaches For Autonomous Vehicles In Civil Airspace: Giving Sight To The Blind, Nicholas Scott Hardman

Masters Theses

The growing prevalence of unmanned aerial vehicles (UAVs) brings great potential for public benefit, but in order to fly in civil airspace UAVs must avoid traffic without the benefit of an onboard human. Developing this capability presents many system integration challenges.

This report examines the integration of automated detect, see, and avoid (DSA) systems on aircraft. For context, the need for UAV operations is reviewed. The report then examines how DSA fits into the entire framework for aviation safety. The research, test results, and conclusions that follow provide the necessary information to decide:

• how to test and evaluate new …

An Experimental Study Of Axisymmetric Cavity Oscillations In Low Speed Incompressible Flow, Jeremy David Brice Smith

Masters Theses

This study is the latest increment of an ongoing research effort at the University of Tennessee Space Institute with the goal of accomplishing a greater understanding of cavity instabilities and or making use of the instabilities to amplify their effects on the flows. An experimental procedure was designed to examine the unsteady pressure pulses that occur when an incompressible fluid (water) flows through an axisymmetric cavity. The length to depth ratios (L/D) examined ranged from about 0.69 to about 6.2, and the average flow Reynolds numbers ranged from 0 to 1.2 million.

Results show that large amplitude oscillations are generated …

Experimental Aerodynamic Analysis Of A Wing-Flap System With Delta Vortex Generators, Charles Roy Mcconnell

Masters Theses

The principle idea upon which the use of vortex generators (VGs) is based has been to control flow separation. The characteristic of VGs has been used to improve lift and alter the stall characteristics of aircraft and has been a relatively common practice for many years. Due to the seemingly limitless range of VG geometries and arrangements, which are largely dependant upon the desired aerodynamic performance, there has been a broad investigation into VG application.

The purpose of this experimental investigation has been to collect data to be used to establish the effects of various delta shaped vortex generators (delta-VGs) …

Managing The Remaining Service Life Of The T-34c Aircraft, John Howard Rousseau

Masters Theses

The T-34C Airplane has been the primary trainer aircraft of the United States Navy for more than twenty-five years and is reaching the end of its service life. The Navy has delayed the procurement of the replacement T-6A Texan II aircraft for five years, yet does not expect the future training requirements to diminish. This delay in T-6A procurement along with recent observed increases in primary trainer aircraft usage have resulted in the need for the Navy to pay considerable attention to the remaining service life of the T-34C aircraft.

This thesis will discuss the methodology used to determine future …

Airy Stress Function For Two Dimensional Inclusion Problems, Dharshini Rao Kavati

Mechanical and Aerospace Engineering Theses

This thesis addresses a problem of finding the elastic fields in a two-dimensional body containing an inhomogeneous inclusion using the Airy stress function which is determined so that the prescribed boundary condition at a far field and the continuity condition of the traction force and the displacement field at the interface are satisfied exactly. All the derivations and solving simultaneous equations are carried out using symbolic software.

Structural Optimization Using Ansys And Regulated Multiquadric Response Surface Model, Ajaykumar Menon

Mechanical and Aerospace Engineering Theses

The high computational expense of large non-linear and complex finite element analysis limits or often prohibits the use of conventional codes in engineering design and multidisciplinary optimization. Consequently alternate methods such as Design of experiments (DOE) and Response surface approximation are commonly used to minimize the computational cost of running such analysis and simulation. The basic approach of such methods is to construct a simplified mathematical approximation of the computationally expensive simulation and analysis code, which is then used in place of the original code to facilitate multidisciplinary optimization, design space exploration, reliability analysis etc. When such codes along with …

Failure Analysis Of Composite Laminates With A Hole By Using Finite Element Method, Moumita Roy

Mechanical and Aerospace Engineering Theses

Predicting the strength of a given laminate has been extensively studied. There have been several fracture models proposed but still the immense tests of composite laminates are still needed. Different material systems or lay-ups exhibit different failure modes and failure mechanisms. This thesis focuses in investigation of the failure mechanism of the [±?/02]s and [02/±?]s laminates with a hole. ANSYS finite element models with and without a crack in vicinity of hole were developed to investigate the effect of the stress distribution due to the presence of the angle ply crack. The stress concentrations were obtained. It is found that …

Modular Multi-Scale Assembly System For Mems Packaging, Rakesh Murthy

Mechanical and Aerospace Engineering Theses

A multi-scale robotic assembly problem is approached here with focus on mechanical design for precision positioning at the microscale. The assembly system is characterized in terms of accuracy/repeatability and calibration via experiments. The MEMS packaging requirements are studied from an assembly point of view. The tolerance budget of the assembly ranges from 4 microns to 300 microns. The system components include robots, microstages, end-effectors and fixtures that accomplish the assembly tasks. Task assignment amongst this hardware has been accomplished based on precision and dexterity availability. Various end-effectors and fixtures have been designed for use with off-the-shelf hardware (robots and microstages) …

Parametric Cycle Analysis For Pulse Detonation Engines, Haider Hekiri

Mechanical and Aerospace Engineering Theses

The performance of an ejector-driven pulse detonation engine (PDE) with an afterburner is analytically estimated. In the analysis, the PDE was modeled as a straight tube, closed at the front end and open at the other. A detonation wave starts to travel after it is ignited at the closed end, causing a Chapman-Jouguet detonation wave followed by a Taylor rarefaction to travel to the open end. At that point, rarefaction waves are reflected back to the closed end. The result is a high thrust due to both the primary and secondary flows of the ejector-driven PDE. A theoretical analysis is …

Design And Analysis Of Multi-Functional Laparoscopic Tool, Vadakkapattu Candadai Venkat Raghavan

Mechanical and Aerospace Engineering Theses

Laparoscopic tools have been developed over many years, but there is a need for a laparoscopic tool that can be used for multiple purposes without the need to be removed and reinserted in the body. This thesis discusses the design of such a multi-functional laparoscopic tool with the ability to independently actuate grasping and shearing mechanisms, and is modular enough to be easily adapted to robot assisted surgical techniques. The envisioned tool can be divided into three main sections - the surgeon interface, the transmission mechanism, and the end effector. The surgeon interface mainly consists of a handle and two …

Reliability Of Lead-Free Solder Under Cyclic Bending, Fahad Zahedi

Mechanical and Aerospace Engineering Theses

To characterize particular compositions of lead free solder, four point cyclic bending test was conducted to study the affects of accelerated stress testing on the package to board interconnects. Nine CTBGA packages with 0.5 mm ball pitch and 12 x 12 mm package size were reflowed on 8 layered PWB's using solder balls with lead free composition alloys and different PWB copper pad finishes. The boards were subjected to test conditions based on proposed standards by JEDEC. Strain gages were mounted at different locations on the test boards as well as on bare boards in order to observe the difference …

Propeller Development Process: Conflict And Cooperation Between The Department Of Defense And Civil Aviation, Nathan Grant Neblett

Masters Theses

The purpose of this thesis was to compare and contrast the acquisition of the Electronic Propeller Control System through both the Department of Defense and Civil Aviation processes controlled by the Federal Aviation Administration (FAA). The author was a planner and participant in the Department of Defense (DoD) process. Information about the Civil Aviation process was obtained via email and telephone communication with participants, some of whom aided both processes.

Strong similarities existed in system design and prototype manufacture for both processes. A large portion of developmental flight test was similar, if not identical. In particular, both the DoD and …

Modeling, Stability, And Control Of A Rotatable Tail On A Micro Air Vehicle, Travis J. Higgs

Theses and Dissertations

This research uses existing experimental wind tunnel data to develop a non-linear model that is used to characterize the stability of a flexible wing Micro Air Vehicle (MAV) with a rotatable tail. The experimental data are curve fit based on either angle of attack or angle of sideslip, and the coupled effect of tail rotation and tail deflection on the force and moment coefficients. Static optimization trims the input and state variables for Steady Level Unaccelerated Flight (SLUF). The resulting initial conditions are fed to an open loop non-linear Simulink/Matlab simulation. The study found that the bare MAV design is …

Bio-Derived Fuels For Hybrid Rocket Motors, Joshua David Scholes

Masters Theses

Two bio-derived fuels have been successfully tested in a laboratory scale hybrid rocket combustion chamber located at the University of Tennessee, Knoxville. Pure lard soaked in an open cell sponge matrix and beeswax were both tested using gaseous oxygen as the oxidizer. Given similar testing conditions, these fuels exhibit higher regression rates than the common hybrid rocket propellant HTPB (hydroxyl-terminated polybutadiene), thus overcoming one of the main shortcomings of hybrid rocket fuels. These fuels also have similar or higher regression rates than paraffin-based fuels recently tested by a Stanford University/NASA Ames team. Measured thrusts ranged from 20-140 Newtons, and calculated …

Performance Measurements Of Direct Air Injection In A Cavity-Based Flameholder For A Supersonic Combustor, Scott G. Edens

Theses and Dissertations

For several years the Air Force Research Lab Propulsion Directorate has been studying the difficulties in fueling supersonic combustion ramjet engines with hydrocarbon based fuels. Recent investigations have focused on the use of direct air injection into a directly-fueled cavity-based flameholder. Direct air injection has been shown qualitatively to be a valuable tool for improving cavity combustion. Little quantitative data is available that characterizes the performance of cavity-based flameholders. The objective of this research was to quantitatively determine the specific advantages and disadvantages of the direct air injection scheme. This was accomplished via intrusive probing into a supersonic free stream …

Arc-Heated Gas Flow Experiments For Hypersonic Propulsion Applications, Christopher Matthew Roseberry

Mechanical and Aerospace Engineering Dissertations

Although hydrogen is an attractive fuel for a hypersonic air-breathing vehicle in terms of reaction rate, flame temperature, and energy content per unit mass, the substantial tank volume required to store hydrogen imposes a drag penalty to performance that tends to offset these advantages. An alternative approach is to carry a hydrocarbon fuel and convert it on-board into a hydrogen-rich gas mixture to be injected into the engine combustors. To investigate this approach, the UTA Arc-Heated Wind Tunnel facility was modified to run on methane rather than the normally used nitrogen. Previously, this facility was extensively developed for the purpose …

Numerical Study Of Chemically Reacting Viscous Flow Relevant To Pulsed Detonation Engines, Tae-Hyeong Yi

Mechanical and Aerospace Engineering Dissertations

A computational fluid dynamics code for two-dimensional, multi-species, laminar Navier-Stokes equations is developed to simulate a recently proposed engine concept for a pulsed detonation based propulsion system and to investigate the feasibility of the engine of the concept.The governing equations that include transport phenomena such as viscosity, thermal conduction and diffusion are coupled with chemical reactions. The gas is assumed to be thermally perfect and in chemically non-equilibrium. The stiffness due to coupling the fluid dynamics and the chemical kinetics is properly taken care of by using a time-operator splitting method and a variable coefficient ordinary differential equation solver. A …

Experimental Characterization Of Femtosecond Laser Micromachining For Silicon Mold Fabrication And Hot Embossing For Polymer Microreplication, Sunil Ranganath Belligundu

Mechanical and Aerospace Engineering Dissertations

Hot embossing is a fabrication technique employed for replicating microfeatures on a polymer surface that was primarily developed to fabricate MEMS devices for microfluidic applications. This manuscript deals with characterization of the femtosecond laser micromachining (FLM) and hot embossing (HEMM) processes for master mold fabrication on silicon and polymer replication respectively. Given the required size of the features to be fabricated or replicated, process parameters for FLM can be determined using the derived empirical equations, process parameters for the HEMM process can be established using the characteristic plots. A novel two-stage embossing process is developed and introduced that employs polymer …

Wind Tunnel Study Of Interference Effects Relating To Aft Supersonic Ejection Of A Store, Timothy P. Jung

Theses and Dissertations

An investigation into the issues surrounding the release of a store into a supersonic wake was conducted. A 10-degree half-angle cone was used to model the carrier vehicle as well as the store. The store was 42% than the vehicle. The experiments were conducted at a freestream Mach number of 2.93 and at zero degrees angle of attack. This study analyzed the effects of a support or strut mounted under the wind tunnel model. Research was conducted on the effects of a store at various positions in the wake, as well as the effects of a rear cavity in the …

Viscosity Measurement Technique By Merging Liquid Drops Aboard The International Space Station, Daniel Aaron Lehman

Masters Theses

The efforts reported in this thesis has been to analyze the data from two "Fluid Merging Viscosity Measurement" experiments in order to validate this as a viable method for measuring the viscosity of fluids with known surface tensions. This method involves simultaneously using a numerical analysis code and experimental data to produce matching curves of contact radius versus time and from that a determination of viscosity. Two experiments that were performed, used different liquids (glycerin and 125 Poise silicon oil) and different size ratios between the two drops ( 1 to 1 and O. 3 3 to 1 respectively). The …

The Thermal Characteristics Of Liquid-Heat-Spreader, Sang Muk Kwark

Mechanical and Aerospace Engineering Theses

The present study is an experimental research of a liquid-heat-spreader (LHS) with saturated water at ~2.29 psia. A LHS, indirect liquid cooling module, was successfully fabricated using thin copper blocks and copper tubes using solder. Three types of LHS, Flat-type, L-type, and T-type, were developed for different orientations and were compared with solid metal blocks such as aluminum and copper. The Flat-type LHS, 100 (W) × 254 (L) × 3 (T) mm3, was designed for vertical orientation. It showed a remarkable thermal performance by dissipating heat flux of 119 W/cm2 with below 100? chip temperature at the typical condition. The …

Investigation Of Pool Boiling Heat Transfer With Nanofluids, Gilberto Moreno

Mechanical and Aerospace Engineering Theses

This investigation conducts pool boiling experiments under saturated conditions (Tsat=60°C) using nanofluids as coolants. Four different nanofluids were tested including zinc oxide (ZnO)-water, aluminum oxide (Al2O3)-water, aluminum oxide (Al2O3)-water+ethylene glycol (ethylene glycol solution) and gold (Au)-water. At saturation (Tsat=60 °C), the pool boiling performance of Al2O3-water and ZnO-water nanofluids were similar. The maximum CHF enhancement as compared to predicted Zuber's [1] CHF evaluated at an equivalent saturation temperature is about 180% for Al2O3-water nanofluids and about 240% for ZnO-water nanofluids. In both cases, no degradation in the boiling heat transfer rate was observed for lower nanoparticle concentrations. The dispersion of …

Tools For Analysis Of Complex Geometries For A Combined Cycle Scram Jet / Rocket, James Moss

Master's Theses - Daytona Beach

A preliminary design for a variable geometry combined cycle supersonic combustion ram jet (SCRAM jet) / rocket was developed. A precise geometry was selected by parametric analysis and the resultant geometry was analyzed using a computational fluid dynamics (CFD) code developed by Dr. Eric Perrell, and modified by, among others, the author.

This paper is broken into several sections discussing, separately, the design innovations used to permit the geometry of the craft to be adjusted to conform to its flight conditions, the 2D analysis tool developed for the parametric analysis, development of the grid for CFD analysis, and modifications made …

A Prediction Code For The Thrust Performance Of Two-Dimensional, Non-Axisynnetric, Converging Diverging Nozzles, Angela M. Geatz

Theses and Dissertations

The objective of this research is to develop a prediction code for the Air Force Research Laboratory Propulsion Directorate that can accurately determine the gross thrust coefficient for a user defined nonaxisymmetric two-dimensional converging diverging nozzle. The code includes the effects of friction, angularity, and expansion losses on nozzle efficiency. To demonstrate the prediction method, the generated computational results were compared to experimental data, as well as computational results from other existing nozzle performance codes, for a number of different nozzle geometries. The nozzle internal performance prediction code showed excellent agreement with experimental data in predicting the gross thrust performance …

Nonlinear Regression Methods For Estimation, Eric B. Nelson

Theses and Dissertations

Regression techniques are developed for batch estimation and applied to three specific areas, namely, ballistic trajectory launch point estimation, adaptive flight control, and radio-frequency target triangulation. Specifically, linear regression with an intercept is considered in detail. An augmentation formulation is developed. Extensions of theory are applied to nonlinear regression as well. The intercept parameter estimate within the linear regression is used to identify the effects of trim change that are associated with the occurrence of a control surface failure. These estimates are used to adjust the inner loop control gains via a feed-forward command, hence providing an automatic reconfigurable retrim …

Operator State Estimation For Adaptive Aiding In Uninhabited Combat Air Vehicles, Christopher A. Russell

Theses and Dissertations

This research demonstrated the first closed-loop implementation of adaptive automation using operator functional state in an operationally relevant environment. In the Uninhabited Combat Air Vehicle (UCAV) environment, operators can become cognitively overloaded and their performance may decrease during mission critical events. This research demonstrates an unprecedented closed-loop system, one that adaptively aids UCAV operators based on their cognitive functional state A series of experiments were conducted to 1) determine the best classifiers for estimating operator functional state, 2) determine if physiological measures can be used to develop multiple cognitive models based on information processing demands and task type, 3) determine …

The Effect Of Aerodynamic Surfaces Versus Thrust Maneuvers On Reentry Vehicles, Meredith M. Albrecht

Theses and Dissertations

This research effort analyzes the effect of aerodynamic surfaces versus thrust maneuvers on a reentry vehicle. At high altitudes the effect of aerodynamic surfaces on the reentry vehicle is small due to low atmospheric density; however as the vehicle reaches lower altitudes a lift maneuver is very successful in deflecting the vehicle and creating a large impact footprint. When a continuous thrust maneuver is input in the place of a lift maneuver the results are very similar at the highest maneuver altitudes, although the impact footprint shrinks rapidly as the maneuver altitude decreases. Additionally, when the thrust maneuver is along …

Effects Of Boundary Layer Flow Control Using Plasma Actuator Discharges, Jeffrey M. Newcamp

Theses and Dissertations

This study addresses the usage and effects of atmospheric plasma discharges on the near wall flow conditions for a Pak-B low-pressure turbine blade. A plasma actuator was built normal to the freestream flow in a low-speed wind tunnel. The test section of the wind tunnel had a contoured upper wall geometry designed to mimic the suction side of a Pak-B turbine blade. A high frequency ac voltage source supplied three voltages in the kilovolt range at four Reynolds numbers in the experiment, between 10,000 and 103,000. The effect of the plasma on the near-wall boundary layer conditions was evaluated at …