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Mechanical and Aerospace Engineering Theses - Archive

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Articles 601 - 630 of 683

Full-Text Articles in Aerospace Engineering

High Temperature Microporous Coatings: The Effects Of Wetting And Wicking On Nucleate Boiling And Chf, Ross Evan Pivovar Jan 2009

High Temperature Microporous Coatings: The Effects Of Wetting And Wicking On Nucleate Boiling And Chf, Ross Evan Pivovar

Mechanical and Aerospace Engineering Theses - Archive

Porous coatings have long been a method to enhance boiling heat transfer. Previous researchers have thoroughly explained most of the physics behind the enhancement, but some holes still exist. Correlations, setup to predict nucleate boiling, are often only accurate in specific scenarios. CHF correlations that take into account wettability do not consider microstructure changes that decrease contact angle, but do not enhance CHF. A solution to these problems is presented via the wicking and wetting of liquid on a porous surface. CHF is found to be enhanced with increases in wicking speeds and flow rate. Wetting, measured by apparent contact …


Transient Flow Analysis Of Filling In Pulse Detonation Engine, Veera Venkata Suneel Jinnala Jan 2009

Transient Flow Analysis Of Filling In Pulse Detonation Engine, Veera Venkata Suneel Jinnala

Mechanical and Aerospace Engineering Theses - Archive

The Pulse Detonation Engine (PDE) is considered to be a propulsion system of future air vehicles. The objective of the present study is to model an efficient inlet system for filling the detonation tube completely with the fuel/air mixture. In the present study the filling processes is modeled numerically using CFD code FLUENTTM. Calculations for the gas flow are carried out by solving the Navier-Stokes equations coupled with the k- ? turbulence model. Five different inlet configurations were proposed and simulated in both two-dimensionally and three-dimensionally. The model with an orifice plate at the inlets ensured the desired optimum results. …


Guidance Of Receiver Aircraft To Rendezvous With Tanker In The Presence Of Wind, Jane-Wit Kampoon Jan 2009

Guidance Of Receiver Aircraft To Rendezvous With Tanker In The Presence Of Wind, Jane-Wit Kampoon

Mechanical and Aerospace Engineering Theses - Archive

This thesis work addresses the problem of aircraft rendezvous in the presence of prevailing wind for automated aerial refueling operations. A modified point-parallel rendezvous procedure is defined. The tanker aircraft performs a racetrack maneuver along a pre-specified refueling orbit. The receiver aircraft enters the refueling area through a fixed point and flies along the refueling line that is aligned with on of the straight legs of the race track. It is the responsibility to meet the tanker at the rendezvous point. A virtual target is used to define the trajectory of the refueling orbit. A nonlinear guidance algorithm is used …


On-Chip Liquid-Liquid Extraction And Separation Using Digital Microfluidics, Praveen Kunchala Jan 2009

On-Chip Liquid-Liquid Extraction And Separation Using Digital Microfluidics, Praveen Kunchala

Mechanical and Aerospace Engineering Theses - Archive

In this thesis, on-chip liquid-liquid microextraction and separation using electrowetting on dielectric (EWOD) digital microfluidics was demonstrated by considering room temperature ionic liquid (RTIL) and DI water as two liquid phases, which form immiscible interface with each other. Room temperature ionic liquids (RTILs) have been actively investigated as replacements for the organic solvents and various "task-specific" ionic liquids (TSIL) are being developed which exhibit many attractive properties such as selectivity to specific biomolecules. Liquid-liquid extraction and separation using EWOD digital microfluidic device with model extraction experiments have been demonstrated, one was extraction of organic dye from RTIL (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [bmim][NTf2]) …


Algorithm Developement For Adaptive Grid Generation Using Galerkin Finite Element Method, Monalkumar Patel Jan 2009

Algorithm Developement For Adaptive Grid Generation Using Galerkin Finite Element Method, Monalkumar Patel

Mechanical and Aerospace Engineering Theses - Archive

The adaptive grid concept is developed in order to achieve more accurate and stable results for the numerical simulations of Partial Differential Equations (PDEs). There are two main types of strategies used for adaptive grids: local refinement by increasing the number of elements (h-refinement) and deforming grids where the number of elements remains fixed (r-refinement). The h-refinement method requires inserting additional elements and nodes in a certain region of the mesh. This significantly affects the software data structure and makes programming more difficult. To maintain the same data structure, the method must delete the same number of nodes from another …


Finite Element Analysis Of Bio-Heat Transfer For Magnetic Fluid Hyperthermia Application, Kamalkumar N. Chauhan Jan 2009

Finite Element Analysis Of Bio-Heat Transfer For Magnetic Fluid Hyperthermia Application, Kamalkumar N. Chauhan

Mechanical and Aerospace Engineering Theses - Archive

Finite Element solution for the multi-region bio-heat Equation is present to model magnetic fluid hyperthermia. This study solves the Penne's two dimensional bio-heat equation using finite element method and develops the thermal behavior of the tumor and healthyportion of the composite tissue using low curie nanoparticles.The inner cylinder represents the tumor tissue containing low Curie temperature nanoparticles. Low Curie temperature nanoparticles generate heat due to the Neel and Brownian relaxation when a magnetic field is applied. The outer cylinder represents the healthy tissue.First part of this thesis discusses about the background related to the nanoparticles heat dissipation and finite element …


Modeling And Simulation Of The Flight Dynamics Of Morphing Wing Aircraft, Borna Obradovic Jan 2009

Modeling And Simulation Of The Flight Dynamics Of Morphing Wing Aircraft, Borna Obradovic

Mechanical and Aerospace Engineering Theses - Archive

Aircraft with variable wing geometry (morphable wings) are of considerable interest, not only for mission-specific optimization, but for enhanced maneuverability as well. In the nascent field of mini- or micro-Unmanned Aerial Vehicles (UAVs), large and rapid changes in wing geometry are achievable, resulting in significant changes of the dynamics of the vehicle. In this thesis, we present a simulation methodology suitable for such aircraft, accounting for the changes in both the aerodynamic and inertial properties. Due to the complexity of the possible wing configurations, the aerodynamics are simulated using an unsteady Vortex-Lattice approach, solved concurrently with six(+) degrees of freedom …


Direct Numerical Simulation Of Interaction Of Detonation Wave With Homogeneous Isotropic Turbulence, Hari Narayanan Nagarajan Jan 2009

Direct Numerical Simulation Of Interaction Of Detonation Wave With Homogeneous Isotropic Turbulence, Hari Narayanan Nagarajan

Mechanical and Aerospace Engineering Theses - Archive

The propagation of a shock or detonation wave through a reactive mixture has been the subject of research for over a century. The basic understanding has been shaped by one-dimensional Euler models, namely, those of Chapman-Jouguet and Zeldovich-Neumann-Doring, despite the fact that the detonation front is multidimensional. Other complications include observations of detonation instability, and spinning and galloping detonations. Recent advances in CFD have made it possible to examine detonation waves in great detail. These studies have revealed the complex nature of detonations that were observed experimentally. Some outstanding issues include the influence of inhomogeneities in the reactive mixture on …


Thermo-Mechanical Interaction Within Engineered Tissue During Freezing, Tenok Dehoyos Jan 2009

Thermo-Mechanical Interaction Within Engineered Tissue During Freezing, Tenok Dehoyos

Mechanical and Aerospace Engineering Theses - Archive

Cryopreservation is the preserving of biological tissues at sub zero temperature. There are many useful applications to cryopreservation such as storing donated organs till they are needed rather than letting them go to waste. When tissues are frozen and thawed, their original functionality and vitality are not usually maintained. It's been shown that when tissue is frozen its mechanical properties change, such as tensile strength and modulus. Each tissue has an extra cellular matrix made up of many collagen fibrils that is responsible for the structural integrity of the tissue. This study is to investigate the structural changes of ECM …


Analytical Thermal Model Of A Generic Multi-Layer Spacerless 3d Package, Erantha Nuwan Rodrigo Aug 2008

Analytical Thermal Model Of A Generic Multi-Layer Spacerless 3d Package, Erantha Nuwan Rodrigo

Mechanical and Aerospace Engineering Theses - Archive

Analytical Thermal Model of a Generic Multi-Layer Spacerless 3D Package Abstract The need for more functions in a single device has lead to die stacking architecture. Although the number of functional die increases further to accommodate package functionality, the overall package dimensions have not increased, they have stayed the same or decreased. Recently, Samsung announce a 16 die stacked device. In order to keep the same package height, alternate stacking structures need to be investigated. One suck opportunity is spacerless die stacking architecture. Using dummy silicon spacers add cost to a package and do not increase the memory of functionality. …


The Lattice Boltzmann Method For Computational Fluid Dynamics Applications, Chinmay Adhvaryu Aug 2008

The Lattice Boltzmann Method For Computational Fluid Dynamics Applications, Chinmay Adhvaryu

Mechanical and Aerospace Engineering Theses - Archive

An analysis of lattice Boltzmann method is presented in this thesis. This analysis contrast with the traditional lattice Boltzmann work, where complex fluids are considered with extended properties. Focus of the current thesis is on the validation and use of lattice Boltzmann method for traditional fluid dynamics. In first part of the document a historical and theoretical background of lattice Boltzmann method is presented. In this part some conclusions are drawn about the stability and other physical characteristics of the lattice Boltzmann method. Second part deals with the computer implementation of the LBM. It also discusses some aspect about practical …


The Development Of A Finite Element Tool For The Calculation Of Beam Cross Section Properties, Bryan Dale Mixon Aug 2008

The Development Of A Finite Element Tool For The Calculation Of Beam Cross Section Properties, Bryan Dale Mixon

Mechanical and Aerospace Engineering Theses - Archive

Cross section properties are crucial in the analysis and design of beams as they play a key role in the determination of the stress state encountered. The development of an FEM tool in MATLAB for the calculation of beam cross section properties will be discussed. Properties of interest include general cross section properties as well as the non-trivial warping-dependent properties for both the unrestrained and restrained cross section conditions for solid and hollow, open and closed sections.


Flip Chip Back End Design Parameters To Reduce Bump Electromigration, Vishal Nagaraj Aug 2008

Flip Chip Back End Design Parameters To Reduce Bump Electromigration, Vishal Nagaraj

Mechanical and Aerospace Engineering Theses - Archive

The advancement in flip chip technology has enabled us to meet the requirement of smaller die size along with the increased functionality. Due to this development in flip chip packaging technology along with higher current carrying requirement of solder bumps, electromigration has now become a reliability concern. In this research, a commercially available finite element tool is adopted in order to study the distribution of current density in eutectic solder bump for variety of back end design parameters. Geometries needed were generated by using Pro/Engineer® Wildfire 3.0 as a Computer-Aided-Design (CAD) tool and were transferred to ANSYS® 10.0, where meshed …


Analysis And Design Of A Hypersonic Scramjet Engine With A Starting Mach Number Of 4.00, Kristen Nicole Roberts Aug 2008

Analysis And Design Of A Hypersonic Scramjet Engine With A Starting Mach Number Of 4.00, Kristen Nicole Roberts

Mechanical and Aerospace Engineering Theses - Archive

When pressures and temperatures become so high in supersonic flight that it is no longer efficient to slow the oncoming flow to subsonic speeds for combustion, a scramjet (supersonic combustion ramjet) is used in place of a ramjet. Currently, the transition to supersonic combustion generally occurs at a freestream Mach number around 5.0 to 6.0. This research details analysis completed towards extending scramjet operability to lower Mach numbers, while maintaining performance at higher Mach numbers within the same flowpath as detailed in the Air Force solicitation AF073-058. The specific goal is to determine whether the scramjet starting Mach number can …


Comparison Of Cooling Performance Of Overhead And Underfloor Supply With Rear Door Heat Exchanger In High Density Data Center Clusters, Ravi K. Udakeri Jul 2008

Comparison Of Cooling Performance Of Overhead And Underfloor Supply With Rear Door Heat Exchanger In High Density Data Center Clusters, Ravi K. Udakeri

Mechanical and Aerospace Engineering Theses - Archive

The power trend for server systems continues to grow thereby making thermal management of Data centers a very challenging task. Although various configurations exist, the raised floor plenum with Computer Room Air Conditioners (CRACs) providing cold air is a popular operating strategy. In prior work, numerous data center layouts employing raised floor plenum and the impact of design parameters such as plenum depth, ceiling height, cold isle location, tile openings and others on thermal performance of data center was presented. The air cooling of data center however, may not address the situation where more energy is expended in cooling infrastructure …


Thermo-Mechanical Solutions In Electronic Packaging: Component To System Level, Aalok Trivedi Jul 2008

Thermo-Mechanical Solutions In Electronic Packaging: Component To System Level, Aalok Trivedi

Mechanical and Aerospace Engineering Theses - Archive

Since the advent of the transistor and integrated circuit, the performance of electronic equipment has increased significantly while footprint of systems at all levels continues to decrease. Recently, the number of transistors on a high end microprocessor has exceeded a billion. All of the above has necessitated considerable improvement in cooling technology and associated reliability. In this era of high heat fluxes, air cooling still remains the primary cooling solution mainly due to its cost and ease of installation and operation. The primary goal of a good thermal design is to ensure that the chip can function at its rated …


Structural Optimization Using Matlab Partial Differential Equation Toolbox And Radial Basis Function Based Response Surface Model, Faisal Tanveer Mosharrof Jul 2008

Structural Optimization Using Matlab Partial Differential Equation Toolbox And Radial Basis Function Based Response Surface Model, Faisal Tanveer Mosharrof

Mechanical and Aerospace Engineering Theses - Archive

As a decision making tool, optimization has become an inseparable part of the modern design process. However, in spite of the advances in computer capacity and speed, the computational time for some complex problems is too high to use conventional solution approach. In order to reduce the computational effort and the cost associated with such type of problems, approximation methods such as response surface methodology (RSM) along with design of experiments (DOE) are used in engineering design optimization. The main idea involves replacing the expensive simulation model during the design and optimization process with a simplified mathematical approximation of the …


Trajectory Optimization Using Collocation And Evolutionary Programming For Constrained Nonlinear Dynamical Systems, Brandon Merle Shippey May 2008

Trajectory Optimization Using Collocation And Evolutionary Programming For Constrained Nonlinear Dynamical Systems, Brandon Merle Shippey

Mechanical and Aerospace Engineering Theses - Archive

Trajectory design and optimization has a broad variety of applications in fields such as aerospace and electrical engineering. The solution of a trajectory that minimizes a cost function subject to nonlinear differential equations of motion and various types of constraints may be obtained by the methods of optimal control theory. A framework is presented for numerical solution of the optimal control problem. The solution is converted to that of a constrained discrete parameter optimization problem. Direct collocation and nonlinear programming are used to perform a local gradient-based search for the optimal solution. A genetic algorithm combined with a shooting method …


Flight Data Analysis And Simulation Of Wind Effects During Aerial Refueling, Timothy Allen Lewis Apr 2008

Flight Data Analysis And Simulation Of Wind Effects During Aerial Refueling, Timothy Allen Lewis

Mechanical and Aerospace Engineering Theses - Archive

This thesis presents an analysis of data obtained in an automated aerial refueling test flight conducted with a KC-135 as the tanker and a Learjet 25 as the surrogate receiver UAV. The purpose is to identify the wind induced by the tanker wake and its effect on the receiver aircraft. From the available flight data, a direct computation of the winds experienced by the tanker and receiver is carried out. The mean variation of the receiver wind is compared with the tanker wind when the receiver is at the observation and contact positions. This results in the identification of the …


Analysis And Optimization Of A Crashworthy Helicopter Seat, Nauman A. L Mhaskar Mar 2008

Analysis And Optimization Of A Crashworthy Helicopter Seat, Nauman A. L Mhaskar

Mechanical and Aerospace Engineering Theses - Archive

The objective of a crashworthy seat is to improve the survivability of occupants (cockpit and cabin) in helicopter crashes. All modern helicopter seats are equipped with an energy absorber to reduce lumbar spine load during crash landing. The main objective of this research is to carry out the structural analysis and optimization of a helicopter crashworthy troop seat assembly using finite element methods. The transient dynamic nonlinear finite element analysis helps in identifying whether the seat structure will survive in a crash landing situation, and optimization helps in reducing the weight of the crashworthy seat. The seat is analyzed using …


Effects Of Edge Distance, Hole Size Ratio And Hole Spacing On Peak Stresses Of Composite Laminate With Multiple Holes, Manishkumar Kheradiya Jan 2008

Effects Of Edge Distance, Hole Size Ratio And Hole Spacing On Peak Stresses Of Composite Laminate With Multiple Holes, Manishkumar Kheradiya

Mechanical and Aerospace Engineering Theses - Archive

Unlike isotropic material, the stress distribution of laminate with a hole varies with its size, its material properties and fiber orientations of each layer. Moreover, presence of a hole in the neighborhood of another hole may also affect their stress distribution, too. The major objective of this study is to determine stress distribution of finite width laminated composite having multiple holes. The effect of stress concentration due to presence of holes in each angle ply of laminated composite is a focus of this study. Three dimensional finite element models are developed to determine the stress distribution in laminate using commercial …


Thermal Design Optimization Of Internally Cooled Turbine Blades, James Daniel Ruiz Jan 2008

Thermal Design Optimization Of Internally Cooled Turbine Blades, James Daniel Ruiz

Mechanical and Aerospace Engineering Theses - Archive

This paper outlines the use of Computational Fluid Dynamics (CFD) and Genetic Algorithm (GA) Optimization to enhance the design of a 3-dimensional internally cooled turbine blade. The optimization code utilizes principles of Genetic Algorithms to optimize (i.e. minimize) the integrated heat flux through the turbine blade. The optimization is accomplished by adjusting the size and position (within pre-determined constraints) of cooling passages internal to the turbine blade. Starting with an aerodynamically optimized airfoil shape, cooling passage designs are generated by the optimization process and coupled with boundary and airfoil domains. The analysis becomes a Conjugate Heat Transfer (CHT) problem analyzing …


Development Of Spectral And Wavelet Time-Of-Flight Methods For Propagating Shock And Detonation Waves, Alfredo Albert Ortiz Jan 2008

Development Of Spectral And Wavelet Time-Of-Flight Methods For Propagating Shock And Detonation Waves, Alfredo Albert Ortiz

Mechanical and Aerospace Engineering Theses - Archive

An accurate time delay estimate for a propagating disturbance, including an estimate of its uncertainty, is important in many areas of science. Several techniques were developed for determining the propagation time of a shock and detonation wave. The speed of the propagating wave was then determined by the time delay estimates provided for the best techniques. The techniques used ranged from the commonly used time-of-flight method to a nonstationary cross-spectral density phase method that provided a statistical estimation of the propagation time. The time delay results for a shock tube experiment showed that most of the methods had difficulties in …


Thermal Analysis Of Pulse Detonation Engines, Raghu Raman Ghandikota Jan 2008

Thermal Analysis Of Pulse Detonation Engines, Raghu Raman Ghandikota

Mechanical and Aerospace Engineering Theses - Archive

The pulse detonation engine (PDE) is a compact system that can be modeled thermodynamically by the Humphrey cycle and is capable of high efficiency. The rapid heat release for stochiometric fuel/oxidizer ratios results in developing high temperatures. The high temperatures produced during its operation can cause the engine to fail. Thus, operating this engine for a longer duration would become dubious if the temperatures are not dissipated from it. The current research aims to perform a preliminary thermal analysis. This analysis consists of two steps. The first step is to determine the heat dissipated from the engine using the unsteady …


Effect Of Pullout And Torsional Strength Of Composites With Co-Molded Thread Inserts, Dan L. Reller Jan 2008

Effect Of Pullout And Torsional Strength Of Composites With Co-Molded Thread Inserts, Dan L. Reller

Mechanical and Aerospace Engineering Theses - Archive

Rotorcraft transmission housings and drive system components are typically made from cast metals due to their highly complex geometries. Utilizing composite materials offers potential to reduce weigh and manufacturing cost while increasing corrosive resistance and extending part life. Traditional compression molded composites have not been utilized in aerospace because they typically experience low fiber volume fraction. Currently there are numerous materials which offer opportunities for composites in drive system housing applications and also offer the ability to co-mold details to reduce post mold operations. One of the issues associated with composite structures is the ability to fasten them to one …


Electromagnetic Flow Control: A Review And Experimental Development And Testing Of A Compact Actuator, Eric Braun Jan 2008

Electromagnetic Flow Control: A Review And Experimental Development And Testing Of A Compact Actuator, Eric Braun

Mechanical and Aerospace Engineering Theses - Archive

This thesis is divided into two sections which both relate to the field of magnetohydrodynamics and particularly electromagnetic flow control (EMFC). The first section contains a review of recent research in EMFC. The second section presents the experimental results of a compact EMFC actuator designed for use at low speeds where the flow conductivity is raised by conductive seed particle injection.Fifty years ago, publications began to discuss the possibilities of using EMFC to improve aerodynamic performance. This led to an era of research that focused on coupling the fundamentals of magnetohydrodynamics (MHD) with propulsion, control, and power generation systems. Unfortunately, …


Finite Element Analysis Of Helicopter Main Rotor Hub Plates To Evaluate The Possibility Of Increasing The Time To Retirement, Douglas Wittig Jan 2008

Finite Element Analysis Of Helicopter Main Rotor Hub Plates To Evaluate The Possibility Of Increasing The Time To Retirement, Douglas Wittig

Mechanical and Aerospace Engineering Theses - Archive

Rotorcraft main rotor systems have multiple components that are subject to very high loads and moments. These loads and moments dictate the life expectancy of the parts based upon the components material of composition. This project will primarily focus on the upper and lower hub plates on the main rotor system of a typical four bladed commercial helicopter. The upper and lower plates are machined from 7075-T73 aluminum forgings. The upper and lower plates were laboratory fatigue tested during product development as supporting parts in the test of the main rotor assembly. With recent advances in finite element analysis, there …


Development Of Optical Fiber Sensors For Distance, Refractive Index And Strain Measurement, Ayan Majumdar Jan 2008

Development Of Optical Fiber Sensors For Distance, Refractive Index And Strain Measurement, Ayan Majumdar

Mechanical and Aerospace Engineering Theses - Archive

This thesis is focused on the development of optical fiber based sensors for the measurement of distance, refractive index, and strain. The fabrication, implementation, analysis, and evaluation of the sensors are presented. The Extrinsic Fabry-Perot Interferometric (EFPI) distance sensor is one of the most popular distance sensors but it possesses an inherent drawback. When the free-space cavity distance is very small, the numbers of fringes generated are not sufficient for the distance demodulation algorithm; therefore the smallest distance it can measure is determined by the bandwidth of the light source. An optical fiber based distance sensor is developed in this …


A Process For Ice Detector Placement Using 3-D Eulerian Droplet Impingement Analysis, Glenn T. Lancaster Jan 2008

A Process For Ice Detector Placement Using 3-D Eulerian Droplet Impingement Analysis, Glenn T. Lancaster

Mechanical and Aerospace Engineering Theses - Archive

Ice detectors invoke an aircraft's ice protection systems, which reduce the risks of flight into known icing conditions. A process has been developed to place ice detectors on aircraft using high fidelity computational icing tools. Three-dimensional Eulerian droplet impingement analysis is used to determine the necessary ice detector height and location required to achieve full functionality. This method is applied to the V-22 Osprey tiltrotor aircraft for validation against both tunnel and flight test data. When compared to icing tunnel test data, computational results for the volume of ice accreted on an antenna were within ten percent, validating the computational …


Visualizing The Flow Induced By An Air Curtain Over A Mannequin Using Stereo Particle Image Velocimetry, John Edward Fernandes Jan 2008

Visualizing The Flow Induced By An Air Curtain Over A Mannequin Using Stereo Particle Image Velocimetry, John Edward Fernandes

Mechanical and Aerospace Engineering Theses - Archive

Air curtains find widespread applications in today's world, such as in malls, supermarkets, airports, cold storage, etc., to allow easy pedestrian movement between two different environments. There is interest in understanding the flow induced by traffic through the air curtain in terms of energy efficiency and the ability to provide isolation from contaminants and airborne pathogens. To develop an understanding of the flow, an initial exploratory study was performed using a static mannequin. A stereo particle image velocimetry (SPIV) system was set up to map the flow of the air curtain, installed on top of the doorway, over a mannequin. …