Engineering Commons^™

A Full-Wave Investigation Of The Use Of A 'Cancellation Factor' In Gw-Airglow Interaction Studies, Yonghui Yu

Master's Theses - Daytona Beach

Atmospheric gravity waves (GWs) perturb minor species involved in the chemical reactions of airglow emissions in the mesopause region of the earth's atmosphere. The so-called 'Cancellation Factor' (CF) is defined as a transfer function relating the amplitude of airglow brightness fluctuation to the amplitude of GW-induced fluctuation in temperature [Swenson and Gardner, 1998]. This transfer factor can be used to determine GW fluxes and the forcing effects of GWs on the mean state through airglow observations, because GW fluxes are proportional to the square of GW amplitude.

Numerical models [Walterscheid et al., 1987; Schubert et al., 1991] have previously shown …

Utilization Of A Piezoelectric Polymer To Sense Harmonics Of Electromagnetic Torque, Jason Neely, Steven Pekarek, Daniel S. Stutts, Philip Beccue

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, the use of a piezoelectric polymer material to measure the harmonics of electromagnetic torque produced by a permanent magnet synchronous machine is described. The advantages of the polymer include low cost, durability, and flexibility. In addition, wide-bandwidth sensors are relatively easy to design and couple to drive system hardware for harmonic evaluation or to use in feedback-based control. To illustrate the use of the polymer, the electrical and mechanical properties of three sensors are described. The results of time-domain simulation and hardware experiments are used to validate that the voltage obtained from the sensors is linearly related …

Microburst Recovery For Jet Transport Aircraft: A Comparison Between Constant And Variable Pitch Guidance Trajectories, Mark Cadmus

Master's Theses - Daytona Beach

The purpose of this research was to compare, in a simulator, the safety of a variable pitch strategy with the established constant pitch strategy in transitioning through a microburst during an abort maneuver in the approach to landing phase of flight. In numerous mathematical and computer studies of microburst penetrations, the variable pitch strategy provided a greater recovery altitude than the constant pitch strategy. A Boeing 737 level C aircraft simulator was employed to evaluate these findings in a dynamic environment. Three appropriately qualified subjects piloted 35 flights through a microburst, while computer generated data were collected. "Safety", defined as …

Cooperative Control Simulation Validation Using Applied Probability Theory, Christopher S. Schulz

Theses and Dissertations

Several research simulations have been created to support development and refinement of teamed autonomous agents using decentralized cooperative control algorithms. Simulation is the necessary tool to evaluate the performance of decentralized cooperative control algorithms, however these simulations lack a method to validate their output. This research presents a method to validate the performance of a decentralized cooperative control simulation environment for an autonomous Wide Area Search Munition (WASM). Rigorous analytical methods for six wide area search and engagement scenarios involving Uniform, Normal, and Poisson distributions of N real targets and M false target objects are formulated to generate expected numbers …

Fifty Years Of Hypersonics: Where We've Been, Where We're Going, John J. Bertin, Russell M. Cummings

Aerospace Engineering

Hypersonic flight has been with us since 22 September 1963, when Robert M. White flew the North American X-15 at 4520 mph at an altitude of 354,200 ft—a Mach number of 6.7! This remarkable achievement was accomplished over six decades due to intensive research and development by a large number of scientists and engineers. In spite of that momentous achievement, designers have found the hypersonic environment to be harsh and non-forgiving. New programs since the 1960s have often uncovered the unknown unknowns, usually the hard way—early flights of new systems have often revealed problems of which the designers were …

An Original Method For Computing Complex Non-Premixed Flows In Chemical Equilibrium, Raphael Cioffl

Master's Theses - Daytona Beach

A novel method for computing chemical equilibrium reactions in three-dimensional reacting fluid flows is introduced in this paper. The originality of the method is that continuity equations are solved for the atomic densities rather than for the molecular species densities, as is the case for non-equilibrium flow calculations. The method is suited for applications to mixing flows in rocket engine combustors, where, due to the typical low convective speed, chemical reaction is best modeled as an equilibrium process. Equilibrium formulations usually describe the flow as a perfect, atomically uniform mix between the fuel and the oxidizer. This assumption tends to …

Design And Development Of A Low-Cost High Range Resolution X-Band Radar, Paul C. Cantu

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Synthetic Aperture Radar (SAR) is one of the main tools for microwave remote sensing because of its multi-dimensional high resolution characteristics and the capability to operate in nearly all weather conditions, day and night. The University of Nebraska-Lincoln (UNL) initiated the design and development of a low-cost airborne SAR in January 2001 to support our Airborne Remote Sensing Program. The objectives of this project are separated into various evolutionary stages. This thesis will focus on the initial phase of design and construction of an X-band high range resolution radar (HRR) using basic RF /microwave and digital components. The following stages …

Special Article. Space Security In A World Of Security And Insecurity, Ibpp Editor

International Bulletin of Political Psychology

This article provides a theoretical analysis from which a space security expert could appreciate the complexity and richness of the space security challenge.

A History Of Space Security, Ibpp Editor

International Bulletin of Political Psychology

This article provides a conceptual infrastructure for thinking about the history of space security.

Computational Challenges In High Angle Of Attack Flow Prediction, Russell M. Cummings, James R. Forsythe, Scott A. Morton, Kyle D. Squires

Aerospace Engineering

Aircraft aerodynamics have been predicted using computational fluid dynamics for a number of years. While viscous flow computations for cruise conditions have become commonplace, the non-linear effects that take place at high angles of attack are much more difficult to predict. A variety of difficulties arise when performing these computations, including challenges in properly modeling turbulence and transition for vortical and massively separated flows, the need to use appropriate numerical algorithms if flow asymmetry is possible, and the difficulties in creating grids that allow for accurate simulation of the flowfield. These issues are addressed and recommendations are made for further …

Numerical Analysis Of An Airfoil Response To An Impinging Gust, Claire M. Lessiau

Master's Theses - Daytona Beach

The BASS code, a nonlinear high-order prefactored compact code is validated on a benchmark problem. The nonlinear response of a loaded airfoil to an impinging vertical gust is investigated in the parametric space of gust intensity and frequency. Computational resources, involving a Linux cluster, were set up and maintained. The code was corrected and adapted to this particular problem. Results are compared with linear solution from the GUST3D solver.

Calibrating Expert Assessments Of Advanced Aerospace Technology Adoption Impact, Bruce A. Conway

Engineering Management & Systems Engineering Theses & Dissertations

This dissertation describes the development of expert judgment calibration methodology as part of elicitation of the expert judgments to assist in the task of quantifying parameter uncertainty for proposed new aerospace vehicles. From previous work, it has been shown that experts in the field of aerospace systems design and development can provide valuable input into the sizing and conceptual design of future space launch vehicles employing advanced technology. In particular (and of specific interest in this case), assessment of operations and support cost implications of adopting proposed new technology is frequently asked of the experts. Often the input consisting of …

Atmospheric Water Vapor Lidar Measurements Using Analog And Photon Counting Techniques, Anuj Maheshkumar Shah

Electrical & Computer Engineering Theses & Dissertations

Atmospheric water vapor measurements are essential for the understanding of Earth's weather and radiation budget, along with the water cycle. The remote sensing Differential Absorption Lidar (DIAL) technique is a commanding method used for water vapor measurements from aircraft, spaceborne, and ground-based platforms. The new unmanned aerial vehicle (UAV) water vapor DIAL system provides great feasibility due to the weight and size limitations. The system has significantly less weight, power consumption, and noise presence, thus making it great for UAV applications.

This thesis discusses a UAV water vapor DIAL system that was designed, developed, and evaluated. The research effort was …

An Experimental Study Of Automotive Wakes For Drag Breakdown, Ilteris Koc

Mechanical & Aerospace Engineering Theses & Dissertations

A key to better performance and fuel economy for both road vehicles and aerospace vehicles is better understanding of the drag and lift mechanisms. Drag and lift can be evaluated computationally or experimentally by using various methods, such as wake surveys. Wake surveys with total pressure rakes, 5-hole rakes, and Particle Image Velocimetry techniques are routinely conducted in wind tunnels to provide insight into the flow field and hence to improve the design of the road vehicles or aircraft. However, systematic decomposition of the wake into components such as profile, induced, or wave drag appears to be further advanced in …

The Conference Proceedings Of The 2003 Air Transport Research Society (Atrs) World Conference, Vol. 2, Brent Bowen, Sveinn Gudmundsson, Tae Hoon Oum, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 03-6

The Conference Proceedings Of The 2003 Air Transport Research Society (Atrs) World Conference, Volume 3, Brent D. Bowen, Sveinn Gudmundsson, Tae Hoon Oum, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 03-7

The Conference Proceedings Of The 2003 Air Transport Research Society (Atrs) World Conference, Volume 5, Brent Bowen, Sveinn Gudmundsson, Tae Hoon Oum, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 03-9

The Conference Proceedings Of The 2003 Air Transport Research Society (Atrs) World Conference, Volume 1, Brent Bowen, Sveinn Gudmundsson, Tae Hoon Oum, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 03-5

Hypersonic Boundary-Layer Stability Across A Compression Corner, Hongwu Zhao

Mechanical & Aerospace Engineering Theses & Dissertations

Stability of a hypersonic boundary-layer over a compression corner was investigated numerically. The three-dimensional compressible Navier-Stokes equations were solved using a fifth-order weighted essentially non-oscillating (ArENO) shock capturing scheme to study the shock wave and boundary-layer interactions. The boundary-layer stability was studied in three distinct regions: upstream of the separation region, inside the separation region and downstream of the separation region. After the mean flow field was computed, linear stability theory was employed to predict the unstable disturbance modes in different flow regions and also to find the most amplified disturbance frequency across the compression corner. Gortler instability computations were …

Piezoelectric Sensor In The Application Of Rolling Bearing Health Monitoring, Yinyin Liu

Mechanical & Aerospace Engineering Theses & Dissertations

A condition-based monitoring concept for rolling element bearings in machinery utilizing a piezoelectric load sensor is investigated in this thesis. The radially polarized cylindrical piezoelectric sensor is modeled in its specific coordinates. The sensor registers the stress occurring in all directions around it. The sensor's behavior due to several typical loads is analyzed. Based on the induced stresses in the sensor, the sensor's output as an electric charge can be obtained using the method of integration.

Considering both the normal and tangential loads distributed on the rolling beating's roller-raceway contact surface, the dynamic stress distribution in the outer raceway was …

A Numerical Analysis Of A Non-Porous, Flexible Upper Airfoil Surface, Asao Omura

Mechanical & Aerospace Engineering Theses & Dissertations

The aerodynamic behavior of the early Wright brothers' airfoils is an important element of the history of aeronautics. Their fabric-covered wings were not constrained to maintain the airfoil shape of their wooden rib substructures and therefore differences in performance between rigid and flexible Wright airfoil shapes can be expected. The purpose of this thesis was to develop a systematic numerical approach that allows an assessment of the influence of the fabric on the overall aerodynamic behavior of the Wright Model B airfoil. The Model B airfoil was chosen because it is the earliest "production" airfoil and has sufficient documentation to …

Nonlinear Response And Fatigue Estimation Of Aerospace Curved Surface Panels To Acoustic And Thermal Loads, Adam Przekop

Mechanical & Aerospace Engineering Theses & Dissertations

This work presents a finite element modal formulation for large amplitude free vibration of arbitrary laminated composite shallow shells. The system equations of motion are formulated first in the physical structural-node degrees of freedom (DOF). Then, the system is transformed into general Duffing-type modal equations with modal amplitudes of coupled linear bending-inplane modes. The linear bending-inplane coupling is due to the shell curvature as well as unsymmetric lamination stacking. Multiple modes, inplane inertia, and the first-order transverse shear deformation for composites are considered in the formulation. A triangular shallow shell finite element is developed from an extension of the triangular …

Nasa - Jpl: Space Adventures By Stanford Students & Mentors, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "NASA - JPL: Space Adventures by Stanford Students & Mentors" from June 25, 2003.

The Multi-Application Survivable Tether (Mast) Experiment, Robert J. Twiggs, Robert Hoyt, Jeffrey Slostad

Robert "Bob" Twiggs STEM Education Collection

An article by Bob Twiigs, Robert Hoyt, and Jeffrey Slostad titled "The Multi-Application Survivable Tether (MAST) Experiment" from June 16, 2003.

Crawl, Walk, Run & Fly: Some Experiments To Try, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Crawl, Walk, Run & Fly: Some Experiments to Try" from June 13, 2003.

Multidisciplinary Applications Of Detached-Eddy Simulation To Separated Flows At High Reynolds Numbers, Scott A. Morton, Matt Steenman, Russell M. Cummings, James R. Forsythe, Kenneth E. Wurtzler, Kyle D. Squires, Shawn H. Woodson, Phillippe R. Spalart

Aerospace Engineering

We focus on multidisciplinary applications of detached-eddy simulation (DES), principally flight mechanics and aeroelasticity. Specifically, the lateral instability (known as abrupt wing stall) of the preproduction F/A-18E is reproduced using DES, including the unsteady shock motion. The presence of low frequency pressure oscillations due to shock motion in the current simulations and the experiments motivated a full aircraft calculation, which showed low frequency high-magnitude rolling moments that could be a significant contributor to the abrupt wing stall phenomenon. DES is also applied to the F-18 high angle of attack research vehicle (HARV) at a moderate angle of attack to reproduce …

Cricketsat Project, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "CricketSat Project" from June 4, 2003.

Design, Modeling And Evaluation Of A 2.4ghz Fhss Communications System For Narcissat, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

An article by Bob Twiigs titled "Design, modeling and evaluation of a 2.4GHz FHSS Communications System for NarcisSat" from June 2, 2003.

Investigation Of The Iced Flowfield Characteristics Related To The Stall Margin Instrumentation Used In Icing Conditions, Erik Pederson

Dissertations

The purpose of this dissertation is to investigate the relationship between the flowfield surrounding an iced airfoil and the stall margin instrumentation developed for use in icing conditions. The stall margin system indicates to the pilot the change in available lift due to ice accretions on the leading edge of an airfoil. This system displays the change in the form of a normalized lift coefficient. Four pressure ports are chosen to specifically maintain a constant calibration curve, for pressure versus normalized lift coefficient, regardless of ice shape. This allows these pressures to be used to determine the change in maximum …

Space Radiation Effects In Electronic Components, Len Adams

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation delivered by Professor Len Adams in May of 2003 on "Space Radiation Effects in Electronic Components."