Aerospace Engineering Commons^™

Data Center Cooling Augmentation Using Micro-Encapsulated Phase Change Material, Ruddhi Shashikumar Deshmukh

Mechanical and Aerospace Engineering Theses - Archive

The ever increasing information technology heat load and data center cooling energy are the main reasons to investigate the performance of microencapsulated phase change slurry over other heat transfer fluids. In recent years, more effort is being made on the development of a new technique to use the phase change materials as pump-able heat transfer fluid and as heat storage system. Thermal Energy Storage (TES) using Phase Change Materials for data centers offers a very effective method of cutting electric power costs for owners and easing demand on the power grid. Thermal storage systems have been around for decades and …

Phoresis Of A Solid Particle In Real Fluid, Yuan Ting Wu

Mechanical and Aerospace Engineering Dissertations - Archive

For micro- and nano-scale particles driven by interfacial non-contact forces in fluid, known as phoresis, this dissertation provides a general formulation and a systematic investigation. It starts with an analytical continuum-mechanics formulation that covers various important aspects of an interfacial structure, including viscosity and mass density variations as well as a body force field, in real fluid. It then reduces to specific solutions due to characteristic mechanisms. A closed-form analytical solution to the case of viscosity variation (which manifests itself as Navier's slip boundary condition) is derived. Furthermore, a novel mechanism for thermophoretic mobility driven by near-surface phase transition is …

Moving Obstacle Detection And Avoidance For Unmanned Ground Vehicle, Gangadhar Rajashekaraiah

Mechanical and Aerospace Engineering Theses - Archive

This thesis presents the development and implementation of an autonomous obstacle avoidance algorithm for UGV (Unmanned Ground Vehicle). The research improves the prior work by enhancing the obstacle avoidance capability to handle moving obstacle as well as stationary obstacles. A mathematical representation of the area of operation with obstacles is formulated by PTEM (Probabilistic Threat Exposure Map). The PTEM quantifies the risk in being at a position in an area with different types of threat. Threat in this context means UGV getting close to or running into stationary and moving obstacles. A LRF (Laser Range Finder) sensor mounted on the …

Computational Flow Analysis Of A Flapping Micro-Flyer Wing For Cycle-Averaged Force Production, Nitesh Rajendra Rajput

Mechanical and Aerospace Engineering Theses - Archive

Human engineers have been trying long to mimic creations of nature for their own benefits. One such area of interest is the insect based micro flapping wing flyers for their wide employment in commercial as well as military applications. These micro air vehicles (MAVs) are capable of performing acts that can be too dangerous for humans to perform, such as tactical reconnaissance in a combat zone. The maneuverability required of these MAVs call for a careful design and thorough study of their aerodynamic performance. This research goal is to provide an estimation of the forces generated during the flapping motion …

Scaling Laws For Radial Foil Bearings, Srikanth Honavara Prasad

Mechanical and Aerospace Engineering Theses - Archive

The effects of fluid pressurization, structural deformation of the compliant members and heat generation in foil bearings make the design and analysis of foil bearings very complicated. The complex fluid-structural-thermal interactions in foil bearings also make modeling efforts challenging because these phenomena are governed by highly non-linear partial differential equations. Consequently, comparison of various bearing designs require detailed calculation of the flow fields (velocities, pressures), bump deflections (structural compliance) and heat transfer phenomena (viscous dissipation in the fluid, frictional heating, temperature profile etc.,) resulting in extensive computational effort(time/hardware). To obviate rigorous computations and aid in feasibility assessments of foil bearings …

Precipitation, Orientation And Composition Effects On The Shape Memory Properties Of High Strength Nitihfpd Alloys, Emre Acar

Theses and Dissertations--Mechanical and Aerospace Engineering

NiTiHf high temperature shape memory alloys are attractive due to their high operating temperatures (>100 ^oC) and acceptable transformation strain compared to NiTi. However, NiTiHf has limitations due to their lack of ductility and low strength, resulting in poor shape memory properties. In this study, Pd has been added to NiTiHf alloys in an attempt to improve their shape memory behavior. A combined approach of quaternary alloying and precipitation strengthening was used.

The characterization of a Ni_45.3Ti_29.7Hf₂₀Pd₅ (at. %) polycrystalline alloy was performed in compression after selected aging treatments. Transmission electron …

A Design Pathfinder With Material Correlation Points For Inflatable Systems, Jared T. Fulcher

Theses and Dissertations--Mechanical and Aerospace Engineering

The incorporation of inflatable structures into aerospace systems can produce significant advantages in stowed volume to mechanical effectiveness and overall weight. Many applications of these ultra-lightweight systems are designed to precisely control internal or external surfaces, or both, to achieve desired performance. The modeling of these structures becomes complex due to the material nonlinearities inherent to the majority of construction materials used in inflatable structures. Furthermore, accurately modeling the response and behavior of the interfacing boundaries that are common to many inflatable systems will lead to better understanding of the entire class of structures. The research presented involved using nonlinear …

Filtered-Dynamic-Inversion Control For Fixed-Wing Unmanned Aerial Systems, Jon Mullen

Theses and Dissertations--Mechanical and Aerospace Engineering

Instrumented umanned aerial vehicles represent a new way of measuring turbulence in the atmospheric boundary layer. However, autonomous measurements require control methods with disturbance-rejection and altitude command-following capabilities. Filtered dynamic inversion is a control method with desirable disturbance-rejection and command-following properties, and this controller requires limited model information. We implement filtered dynamic inversion as the pitch controller in an altitude-hold autopilot. We design and numerically simulate the continuous-time and discrete-time filtered-dynamic-inversion controllers with anti-windup on a nonlinear aircraft model. Finally, we present results from a flight experiment comparing the filtered-dynamic-inversion controller to a classical proportional-integral controller. The experimental results show …

Multidimensional Modeling Of Pyrolysis Gas Transport Inside Orthotropic Charring Ablators, Haoyue Weng

Theses and Dissertations--Mechanical and Aerospace Engineering

During hypersonic atmospheric entry, spacecraft are exposed to enormous aerodynamic heat. To prevent the payload from overheating, charring ablative materials are favored to be applied as the heat shield at the exposing surface of the vehicle. Accurate modeling not only prevents mission failures, but also helps reduce cost. Existing models were mostly limited to one-dimensional and discrepancies were shown against measured experiments and flight-data. To help improve the models and analyze the charring ablation problems, a multidimensional material response module is developed, based on a finite volume method framework. The developed computer program is verified through a series of test-cases, …

Load Transfer In An Isolated Particle Embedded Within An Epoxy Matrix, Erik Durnberg

Electronic Theses and Dissertations

Particulate composites are widely used in many aerospace applications such as protective coatings, adhesives, or structural members of a body and their mechanical properties and behavior have gained increasing significance. The addition of modifiers such as alumina generally leads to improved mechanical properties. This addition also enables the non-invasive study of the load transfer between the particle and the matrix. Understanding the load transfer between the particulate and the matrix material is the first step to understanding the behavior and mechanical properties of the composite as a whole. In this work, samples with an isolated alumina particle embedded in an …

Ignition Studies Of Diisopropyl Ketone, A Second-Generation Biofuel, Owen Pryor

HIM 1990-2015

This thesis focuses on ignition of diisopropyl ketone (DIPK), a new biofuel candidate that is produced by endophytic conversion. The ignition delay times behind reflected shockwaves were modeled in a high-pressure shock tube. The ignition delay times were compared to other biofuels and gasoline surrogates. Parametric studies of the ignition delay experiments were performed between 1-10 atm and 900 -1200K. An OH optical sensor was developed in conjunction for the ignition delay experiments. The OH optical sensor uses a microwave discharge lamp to generate light at 308 nm that will then be shined through the combustion reaction. Using Beer-Lambert law …

Nondestructive Analysis Of Advanced Aerospace Materials Via Spectroscopy And Synchrotron Radiation, Albert Manero

Electronic Theses and Dissertations

Advanced aerospace materials require extensive testing and characterization to anticipate and ensure their integrity under hostile environments. Characterization methods utilizing synchrotron X-Ray diffraction and spectroscopy can decrease the time required to determine an emerging material's readiness for application through intrinsic information on the material response and failure mechanisms. In this study, thermal barrier coating samples applicable to turbine blades of jet engines were studied using Raman and Photoluminescence spectroscopy as well as Synchrotron X-ray diffraction while Kevlar based fiber composites applicable to ballistic resistant armor were studied using Raman spectroscopy to investigate the mechanical state and corresponding damage and failure …

Keeping The Skies Safe, Massood Towhidnejad, Andrew J. Kornecki

Department of Electrical Engineering and Computer Science - Daytona Beach

Professors Massood Towhidnejad and Andrew Kornecki shine a light on how their lab is helping government and the aviation industry to enhance the safety and security of software-intensive systems.

Extremum-Seeking For Nonlinear Discrete-Time Systems With Application To Hcci Engines, H. Zargarzadeh, S. Jagannathan, J. A. Drallmeier

Electrical and Computer Engineering Faculty Research & Creative Works

For many control applications, identifying an optimal operating point by maximizing/minimizing a performance function is important. This paper applies the extremum-seeking method to nonaffine, nonlinear discrete-time systems stabilized by an optimal adaptive controller. First, a novel averaging method is used for the nonlinear discrete-time systems to show that their output unique extrema are stable equilibrium points. Then, a singular perturbation method in discrete time is employed to show that the overall closed loop system will dynamically converge to the extremum. The applicability of this scheme is numerically verified on a Homogeneous Charge Compression Ignition (HCCI) model validated experimentally and expressed …

Space Tourism: Hurdles And Hopes, Robert A. Goehlich

Publications

According to the Space Policy Institute (2002, Bib. section), “Space tourism is the term broadly applied to the concept of paying customers traveling beyond Earth’s atmosphere.” Operating reusable launch vehicles (RLVs) might be a first step toward achieving mass space tourism. Thus, the aim of this article is to investigate the potential hurdles and other aspects of importance that must be overcome in order to use RLVs for space tourism flights. The primary ones are social issues (e.g., “Is space tourism ethically acceptable?”), institutional issues (e.g., “Is environmental pollution caused by space tourism more harmful than other emission sources?”), and …

Robust And Adaptive Nonlinear Control Of Limit Cycle Oscillations In Uavs Using Synthetic Jet Actuators, Natalie Ramos Pedroza

Doctoral Dissertations and Master's Theses

Limit cycle oscillations (LCO), also known as utter, cause significant challenges in fight control of unmanned aerial vehicles (UAVs), and could potentially lead to structural damage and catastrophic failures. LCO can be described as vibrational motions in the pitching and plunging displacements of an aircraft wing. Even in low Reynolds number (low-Re) fight regimes, LCO can exceed the limiting boundary for safe UAV fight. Further, as practical considerations motivate the design of smaller, lighter weight UAVs, there is a growing need for UAV systems that do not require heavy mechanical actuators (e.g., ailerons). To address this, the use of synthetic …

Development And Operation Of The Pocketqube T-Logoqube, Kevin Zack

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Kevin Zack titled "Development and Operation of the PocketQube T-LogoQube" from April 22, 2014.

Identifiability Of Additive Actuator And Sensor Faults By State Augmentation, Suresh M. Joshi, Oscar R. Gonzalez, Jason M. Upchurch

Electrical & Computer Engineering Faculty Publications

A class of FDI (fault detection and identification) methods for bias-type actuator and sensor faults was explored from the point of view of fault identifiability. The methods use banks of Kalman-Bucy filters (KBFs) to detect faults, determine the fault pattern, and estimate the fault values. A complete characterization of conditions for identifiability of bias-type actuator faults, sensor faults, and simultaneous actuator and sensor faults was presented. It was shown that FDI of simultaneous actuator and sensor faults is not possible using these methods when all sensors have unknown biases. The fault identifiability conditions were demonstrated via numerical examples. The analytical …

A Low Cost Implementation Of Autonomous Takeoff And Landing For A Fixed Wing Uav, Thomas Carnes

Theses and Dissertations

The take-off and landing of an Unmanned Aerial Vehicle (UAV) is often the most critical and accident prone portion of its mission. This potential hazard coupled with the time and resources necessary to train a remote UAV pilot makes it desirable to have autonomous take-off and landing capabilities for UAVs. However, a robust, reliable, and accurate autonomous takeoff and landing capability for fixed-wing aircraft is not an available feature in many low-cost UAV flight control systems. This thesis describes the design of an autonomous take-off and landing algorithm implemented on an existing low-cost flight control system for a small fixed …

Improving Plasma Actuator Performance At Low Pressure, And An Analysis Of The Pointing Capabilities Of Cubesats Using Plasmonic Force Propulsion (Pfp) Thrusters, Paul Daniel Friz

Masters Theses

"This thesis details the work done on two unrelated projects, plasma actuators, an aerodynamic flow control device, and Plasmonic Force Propulsion (PFP) thrusters, a space propulsion system for small satellites.

The first half of the thesis is a paper published in the International Journal of Flow Control on plasma actuators. In this paper the thrust and power consumption of plasma actuators with varying geometries was studied at varying pressure. It was found that actuators with longer buried electrodes produce the most thrust over all and that they substantially improved thrust at low pressure. In particular actuators with 75 mm buried …