Aerospace Engineering Commons^™

Examination Of Micromotion-Induced Transient Effects Of Brain Tissue Interfaced With A Neural Probe, Michael A. Polanco

Mechanical & Aerospace Engineering Theses & Dissertations

Neural probes are utilized to obtain information regarding the activity of brain cells for neural stimulation. The functional longevity of a probe is dependent upon its ability to minimize injury risk during insertion and the recording period in vivo, which could be related to micromotion-related strain between the probe and surrounding tissue. A series of finite element analyses were conducted using the nonlinear transient dynamic code LSDYNA (LSTC, Livermore, CA) to study the strain induced within the brain in an area around a neural probe. A variety of displacement pulses were input into the brain, first where a high magnitude, …

An Investigation Of Unsteady, In-Cylinder Flows Of A Mock-Up Internal Combustion Engine Using Particle Image Velocimetry, David Schleeper

Mechanical & Aerospace Engineering Theses & Dissertations

Particle Image Velocimetry is frequently used in fluid mechanics and aerodynamics research to provide accurate, quantitative information on the instantaneous structure of a variety of flow fields. This technique provides a nonintrusive means of capturing vital, whole-field details of internal and external flows, such as vortex size and strength, not usually possible through other flow investigation techniques. Due to practical difficulties, the utilization of this method for the study of combustion chamber flow within an internal combustion engine is still relatively uncommon. This study used a TSI Particle Image Velocimetry system to identify two-dimensional flow patterns and velocities on a …

Identifiability Of Additive, Time-Varying Actuator And Sensor Faults By State Augmentation, Jason M. Upchurch

Electrical & Computer Engineering Theses & Dissertations

Faults in dynamical systems can have serious safety and reliability implications. For example, actuator and sensor faults have been factors in past incidents and mishaps in many aerospace systems. A large body of research is devoted to developing methods to detect and identify actuator and sensor faults in such systems.

One fault detection and identification menthol employs state augmentation, whereby a set of time-varying faults of interest are modeled as outputs of exogenous linear, time-invariant systems and augmented to the state of the nominal system model. The resulting model represents the system dynamics due to a particular actuator-sensor fault configuration. …

Correlational Study Of Open Circuit Resonant (Sansec) Sensor’S Electric Field Distribution On Lightning Attachment, Kayla M. Farrow, Linda L. Vahala

Electrical & Computer Engineering Faculty Publications

NASA Langley Research Center (LaRC) is conducting research to develop an open circuit SansEC (Sans Electric Connection) sensor to provide lightning strike protection (LSP) in conjunction with damage detection and diagnosis for composite aircraft. SansEC sensors are simplistic devices consisting of an open circuit conductive trace shaped in a planar geometric spiral. The length and width of the conductive trace as well as the gap separation between adjacent turns determines the inductance, resistance and capacitance of the LRC circuit and its associated resonant response. When the sensor is placed on a composite substrate, the electric impedance of the substrate is …

Conceptual Design Of A Reusable Mars Aircraft, Bryce L. Horvath

Mechanical & Aerospace Engineering Theses & Dissertations

This study assumes that the launch vehicles and precision Mars entry descent and landing systems, required for eventual crewed missions to the surface, have been developed, motivating the rapid build-up of a fixed surface base to enable extended human stays. During the time interval between the first successful placement of a heavy (between 20 and 80 metric ton) payload and completion of the baseline human-rated Mars outpost, it will be possible to utilize this large payload delivery capability to accelerate robotic exploration of the surface from the fixed base location.

One element of such an expanded robotic exploration program will …

Use Of A Rolling Road System In Crosswind Conditions, Mau-Kuo Chen

Mechanical & Aerospace Engineering Theses & Dissertations

Wind tunnel testing continues to play an important role in vehicle aerodynamic development. Accurate results are strongly associated with whether the wind tunnel can closely simulate the on-road conditions, including the Reynolds number and all boundary conditions. Rolling road systems (or moving belts) have been a successful tool for many auto makers and racing teams to simulate the relative motion between the stationary vehicle model and the floor in the test section. The mechanism of the rolling road system is simple, but how it affects the adjacent flow field and how this flow interacts with the flow underneath the vehicle …

Control Design And Implementation For An Autonomous Surface Vehicle Using Azimuth Thrusters, Stanton James Coffey

Mechanical & Aerospace Engineering Theses & Dissertations

Autonomous Surface Vehicle research for water applications is inspired by a technological push to create more automated robotics that can perform functions too menial for a human to spend time on as well as too complex, difficult, or dangerous for a person to perform. The development objective is to construct, program, and test an autonomous surface vehicle that can perform precision hold maneuvers independent of human control. This capability would be useful in many situations where it is desirable to freeze the current position of the boat in order to perform some duty task. To conduct the research for this …

Design Advantages Of Skin Friction Drag Reduction Using Riblets, John Michael Gregory

Mechanical & Aerospace Engineering Theses & Dissertations

The research reported here has examined the potential improvements in overall aircraft performance that can result from integrating skin friction reduction technology, such as riblets, early in the aircraft design cycle. This study has shown that riblets can improve the payload capacity, increase the range, and improve performance of transport aircraft. If recent advances in fabrication techniques make it possible to create aluminum wing surfaces with integral riblet geometries, the applications could be widespread and the gains significant.

Active-Twist Rotor Blades Design, Analysis, And Testing, Andrew Randall Kreshock

Mechanical & Aerospace Engineering Theses & Dissertations

The subject of this thesis is the design, analysis, and experimental assessment of active-twist rotors. These active rotors use piezoelectric actuators embedded in the skins to twist the blade to reduce vibratory loads in the fixed system. First, the design and optimization of the twist response within the geometric and structural constraints of a rotor blade is presented. A parametric analysis is conducted varying the airfoil thickness, active-material placement, and structural plies to determine the maximum static twist response. A Macro-Fiber Composite (MFC), which is a fibrous piezoelectric device is used as the active material. Analyses of the cross-section are …

Section Abstracts: Aeronautical And Aerospace Sciences

Virginia Journal of Science

Abstracts of the Aeronautical and Aerospace Sciences Section for the 91st Annual Virginia Journal of Science Meeting, May 2013

Characterization Of A Spiral Microfluidic Focusing Device For Continuous Single Cell Impedance-Based Cytometry Applications, Daniel Riley

Mechanical & Aerospace Engineering Theses & Dissertations

A major focus in the field of cell characterization is the quantification of cell dielectric properties in order to develop low-cost, portable microfluidic devices that can, among other things, perform point-of-care detection of rare diseases and complete blood counts. Impedance-based cytometry has become an advantageous tool to ascertain these properties, wherein it is important that cells pass through the same point in a channel cross-section one at a time to ensure accurate and repeatable readings. This study documents the assessment of an 8-loop 160 μm (W) x 80 μm (H) spiral microchannel used to focus 10 μm polystyrene particles. In …

Micro--Piv Measurements And Numerical Simulations Of Induced Charge Electro-Osmosis Around A Conducting Metal Rod, William George Rosen

Mechanical & Aerospace Engineering Theses & Dissertations

The induced charge electro-osmotic (ICEO) flow around a conducting metal rod positioned in the center of a microchannel was analyzed through physical experimentation and numerical simulation. The experimental set up consisted of a straight microchannel connecting two fluid reservoirs with a square wave AC electric field applied across the microchannel. The electric field for the experimental tests ranged from 100 V /cm to 200 V/cm at frequencies from 500 Hz to 1.5 kHz. The numerical simulations used a similar geometric setup but were exposed to both a direct current (DC) and alternating current (AC) applied electric field. The electric field …

Nonlinearity Index Analysis Of Periodic-Chaotic Stall-Spin Aircraft Motion, Daniel Paul Tapolcai

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis explores the application of nonlinearity index theory to the nature of stalling and spinning aircraft motions. Nonlinear dynamic phenomena related to stall and spin have been a concern to flight engineers and pilots for generations. Considerable past work has been directed to detect and understand the cause and nature of these phenomena. Methods such as bifurcation analysis, Volterra expansion series, and nonlinear simulation are a few of the nonlinear approaches developed to study this topic. Traditionally, however, linear analysis is the most widely used approach for studying aircraft dynamical behavior under a given set of acceptable conditions. This …

Investigation Of Buoyant Transport Systems For Martian Exploration, Jake A. Tynis

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis has investigated the feasibility of utilizing hydrogen-filled balloons as transport systems to accelerate robotic exploration of Mars. Assuming that a fixed robotic base is established at a Mars surface location that is accessible to water ice, electrolysis of in situ water to produce hydrogen is straight forward. A recent Master's thesis determined that global wind patterns at Mars were strong at most times of the year and predictable. On that basis, it was possible to investigate the feasibility of employing surface-launched, hydrogen-filled balloons to transport 100 kg payloads over great distances and to otherwise inaccessible locations throughout Mars. …

Non-Equilibrium Pressure Control Of The Height Of A Large-Scale, Ground-Coupled, Rotating Fluid Column, R. L. Ash, I. R. Zardadhkan

Mechanical & Aerospace Engineering Faculty Publications

When a ground-coupled, rotating fluid column is modeled incorporating non-equilibrium pressure forces in the Navier-Stokes equations, a new exact solution results. The solution has been obtained in a similar manner to the classical equilibrium solution. Unlike the infinite-height, classical solution, the non-equilibrium pressure solution yields a ground-coupled rotating fluid column of finite height. A viscous, non-equilibrium Rankine vortex velocity distribution, developed previously, was used to demonstrate how the viscous and non-equilibrium pressure gradient forces, arising in the vicinity of the velocity gradient discontinuity that is present in the classical Rankine vortex model, effectively isolate the rotating central fluid column from …

Modelling And Configuration Control Of Wing-Shaped Bi-Stable Piezoelectric Composites Under Aerodynamic Loads, Andres F. Arrieta, Onur Bilgen, Michael I. Friswell, Paolo Ermanni

Mechanical & Aerospace Engineering Faculty Publications

Bi-stable composites have been considered for morphing applications thanks to their ability to hold two statically stable shapes with no energy consumption. In this paper, the modelling of the dynamic response of cantilevered wing-shaped bi-stable composites is presented. To this end, an analytical model approximating the dynamic response about each statically stable shape of wing-shaped bi-stable composites is derived. Theoretical modal properties are obtained to attain or stabilise a desired configuration following a previously introduced resonant control strategy. The resonant control technique is evaluated for a wing-shaped bi-stable composite subject to aerodynamic loads. Wind tunnel experiments are conducted on a …

Unmanned Autonomous Object Retrieval: Old Dominion University 2013 International Aerial Robotics Competition Entry, Johnathan Bailey, Austin Boyd, Chung-Hao Chen, Stephen Dailey, Lisa Henderson, Jeremy Stuart, Christina Williams

Electrical & Computer Engineering Faculty Publications

This paper describes the design implementation of a Quadrotor Unmanned Aerial Vehicle (UAV) with the capability of exploring indoor locations without the assistance of external aids. For relative position, the use of a laser range sensor, an optical flow sensor, and sonar sensor combined allows for the vehicle to generate mapping information. With relative position in mind, the vehicle uses vision algorithms to recognize immediate obstacles, sign, and entry ways to allow for quick movement responses and object recognition. A proportional-integral-differentiator controller allows for flight stability and mitigation in the tight confines of the indoor spaces. A mapping algorithm allows …

Modeling Martian Planetary Entry Descent And Landing Using Monte Carlo Driven Response Surface Methodology, Narcrisha S. Norman

Mechanical & Aerospace Engineering Theses & Dissertations

Response surface methodology (RSM) is a statistical method that explores the relationships between several descriptive variables and one or more response variables. For over sixty years, among other areas, it has been utilized in quality engineering, process engineering, aircraft engineering, economics, chemical engineering, automotive engineering and design/technique optimization. In this dissertation, RSM is utilized to produce regression models that represent the planetary entry, descent and landing (EDL) process. A complete understanding of EDL process is an essential component of any planetary exploration. Research in this area is ongoing and confidence in the ability to explore known celestial bodies is growing. …

Modification And Application Of A Turbulence Response Analysis Method For Flexible Aircraft Configurations, Christie Jeanne Funk

Mechanical & Aerospace Engineering Theses & Dissertations

A software program and associated methodology to study gust loading on aircraft exists for a classification of geometrically simplified flexible configurations. This program consists of a simple aircraft response model with two rigid and three flexible symmetric degrees of freedom and allows for the calculation of various airplane responses due to a discrete one-minus-cosine gust as well as continuous turbulence. Simplifications, assumptions, and opportunities for potential improvements pertaining to the existing software program are first identified, then a revised version of the original software tool is developed with improved methodology to include more complex geometries, additional excitation cases, and output …

Configuration Studies Of Electrostatic And Magnetostatic Active Space Radiation Shielding, Trac K. Nguyen

Electrical & Computer Engineering Theses & Dissertations

Developing successful and optimal solutions for mitigating the hazards of radiation in deep space is critical for the success of deep-space long duration explorations, including mission to the Moon, Mars and beyond. A recent report (Tripathi et al., 2008) had explored the feasibility of using electrostatic shielding in conjunction with state-of-the-art materials shielding technologies.

In this thesis research, we study the active electrostatic shielding strategy and examine a hybrid configuration that utilizes both electrostatic and magnetostatic fields. The main advantages of this system are shown to be: (i) much lower magnetic fields that could be below the thresholds set for …

The Influence Of Non-Equilibrium Pressure On Rotating Flows, Irfan Rashid Zardadkhan

Mechanical & Aerospace Engineering Theses & Dissertations

This study was undertaken to investigate the influence of pressure relaxation on steady, incompressible flows with strong streamline curvature. In the early part of this dissertation research, the significance of non-equilibrium pressure forces in controlling the structure of a steady, two dimensional axial vortex was demonstrated. In order to extend the study of pressure relaxation influences on more complex rotating flows, this dissertation has examined other rotating flow features that can be associated with hurricanes, tornadoes and dust devils. To model these flows, modified boundary layer equations were developed for a fluid column rotating near a solid plane including the …

Response Surface Optimization Of Electron Beam Freeform Fabrication Depositions Using Design Of Experiments, Patricia A. Quigley

Engineering Management & Systems Engineering Theses & Dissertations

The Electron Beam Freeform Fabrication (EBF³ ) System is a material depositing, layer additive technique that produces three dimensional (3D) parts out of a wide range of metals in high vacuum, using an electron beam and wire feedstock. Screening deposition trials on a titanium alloy, Ti-6Al-4V, at the National Aeronautics Space Administration (NASA) revealed selective vaporization of the aluminum content of linear prototypes when subjected to chemical analysis. In this study, the aluminum content, bead height and bead width output responses were analyzed from a systematic study of the effects that the interactions of the EBF³ processing parameters …

Modeling, Identification, Validation And Control Of A Hybrid Maglev Ball System, Ahmed Elhussein E. Mekky

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, the electrodynamics of a single axis hybrid electromagnetic suspension Maglev system was modeled and validated by applying it to a single axis hybrid maglev ball experiment. By exploring its linearized model, it was shown that the single axis hybrid Maglev ball has inherently unstable dynamics. Three control scenarios were explored based on the linearized model; (1) Proportional, Deferential (PD) control, (2) Proportional, Deferential, Integral (PID) and (3) PID controller with pre-filtering. This thesis has shown that a PID controller with a pre-filtering technique can stabilize such a system and provide a well-controlled response.

A parametric system identification …

A Design Of Experiments Approach To Visor Drag Reduction On Heavy Vehicles Using Wind Tunnel Testing, Adam Golembeski

Mechanical & Aerospace Engineering Theses & Dissertations

Drag reduction on a scale wind tunnel model of a tractor and partial trailer was used as a case study to investigate the use of Designed Experiments. Specifically, the drag reduction benefits of replacing a tractor sunvisor with an airfoil shaped sunvisor were investigated. The airfoil-shaped sunvisor was theorized to generate thrust in the direction of travel thus reducing the net drag force. The drag force was measured using a load cell integrated into the tractor-trailer model. The experimental factors were the angle of attack, the horizontal position relative to the surface of the tractor body, the yaw angle and …

A Multi-Objective Differential Evolution Algorithm For Engineering Design Optimization, Shantanu S. Muluk

Mechanical & Aerospace Engineering Theses & Dissertations

The current research investigation focuses on the development of a multi-objective global optimizer based on the differential evolution algorithm. A rotationally invariant version of the original differential evolution algorithm is adopted as the core component of the optimization procedure. The optimizer is applied to a number of multi-objective problems: constrained problems, problems of high dimensionality, and problems with non-convex Pareto fronts.

The effectiveness of the proposed optimization framework in real engineering design problems is demonstrated by carrying out an aerodynamic shape optimization of wind turbine airfoils. The investigation focuses on both thin and thick airfoils. The produced Pareto-optimal airfoil shapes …

Measurement System Characterization In The Presence Of Measurement Errors, Sean A. Como

Mechanical & Aerospace Engineering Theses & Dissertations

In the calibration of a measurement system, data are collected in order to estimate a mathematical model between one or more factors of interest and a response. Ordinary least squares is a method employed to estimate the regression coefficients in the model. The method assumes that the factors are known without error; yet, it is implicitly known that the factors contain some uncertainty. In the literature, this uncertainty is known as measurement error. The measurement error affects both the estimates of the model coefficients and the prediction, or residual, errors. There are some methods, such as orthogonal least squares, that …

Section Abstracts: Aeronautical And Aerospace Sciences

Virginia Journal of Science

Abstracts of the Aeronautical and Aerospace Sciences Section for the 90th Annual Meeting of the Virginia Academy of Science, May 23-25, 2015. Norfolk State University, Norfolk, Virginia.

Effect Of Emergent Technologies On Aircraft Fuel Burn By Seat Class, Lee Matthew Watkins

Mechanical & Aerospace Engineering Theses & Dissertations

In this research, a set of advanced technologies collectively referred to as N+2 technologies, are applied to representative aircraft for seven different seat classes. This study will give a better understanding of which technologies will benefit aircraft of differing sizes compared to current studies which have focused on the fuel efficiency benefits of the N+1 technologies for one size of aircraft. Technologies applied consist of hybrid wing body (HWB) platforms, boundary layer ingestion (BLI) engines, weight reducing technologies, hybrid laminar flow control (HLFC) and advanced engine technologies. The aircraft are modeled in Flight Optimization System (FLOPS), a program developed at …

De-Centralized And Centralized Control For Realistic Ems Maglev Systems, Mohamed M. Aly M. Moawad

Mechanical & Aerospace Engineering Theses & Dissertations

A comparative study of de-centralized and centralized controllers when used with real EMS Maglev Systems is introduced. This comparison is divided into two parts. Part I is concerned with numerical simulation and experimental testing on a two ton six-magnet EMS Maglev vehicle. Levitation and lateral control with these controllers individually and when including flux feedback control in combination with these controllers to enhance stability are introduced. The centralized controller is better than the de-centralized one when the system is exposed to a lateral disturbing force such as wind gusts. The flux feedback control when combined with de-centralized or centralized controllers …

Earth Observation Time Estimates Using Curve Fitted Perturbed Orbit Tracks, Taner Gundogdu

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, time to observation for a generic perturbed low Earth orbit satellite, which is tasked, for reconnaissance of a given surface target is investigated. A curve fitting concept applied to past orbital track data is used to estimate and predict the overflight observation time. The least squares method is selected for the curve fitting process and used for both linear and non-linear aspects. Since orbital track data for actual spacecraft are not widely available, numerical integration of the governing motion equations is used as an alternate data source. One of the numerical integration methods, fourth-order Runge-Kutta, is used …