Aerospace Engineering Commons^™

Mixed H2-H∞ Optimization With Multiple H Infinity Constraints, Julio C. Ullauri

Theses and Dissertations

A general mixed H₂/H_∞ optimal control design with multiple H_∞ constraints is developed and applied to two systems, one SISO and the other MIMO. The SISO design model is normal acceleration command following for the F- 16. This design constitutes the validation for the numerical method, for which boundaries between the H₂ design and the H_∞ constraints arc shown. The MIMO design consists of a longitudinal aircraft plant (short period and phugoid modes) with stable weights on the H₂ and H_∞ transfer functions, and is linear- time-invariant. The controller order is reduced …

Design And Analysis Of A Mode B And Mode Jd Satellite Earth Station, Dennis J. Hance

Theses and Dissertations

This thesis focuses on the design, integration, and analysis of an amateur radio service mode B and mode JD satellite earth station. Preliminary designs were investigated to determine the optimum configuration for the earth station. Modern digital modems, cabling structures, an 80386-based computer system, satellite tracking software, transmission and reception antennas, preamplifiers, and sophisticated performance measurement technologies were integrated into a functioning earth station. Initially, component availability and station design dictated the selection and acquisition of the requisite station equipment, integration of the transmitter, receiver preamplifiers, antennas, and computer equipment followed. Preliminary testing of the various components in the integration …

Calibration And Initial Testing Of A New Hydraulic Simulator, Cristian A. Puebla

Theses and Dissertations

In the present research, the flow field associated with the ejection of a crew capsule from the fuselage of a high speed generic aircraft was experimentally investigated by means of the modified gas hydraulic analogy. For this, an existing hydraulic simulator was calibrated and modified to adapt it to the needs of the experiment. The analogy was evaluated for a five-sided capsule alone, and good quantitative agreement with the 2-D shock-expansion theory was obtained. It was found that the size of the model played a key role in the determination of good quantitative data. The analysis of the capsule interacting …

Computational Investigation Of An Improved Cowl Concept For Hypersonic Propulsive Nozzles, Mark C. Butler

Theses and Dissertations

The effects of placing a gas generator into the cowl of a hypersonic nozzle/afterbody were investigated computationally. Gas generator mass flow and deflection angle effects were analyzed for two nozzle/cowl geometries; an experimentally validated nozzle/cowl configuration evaluated at off-design conditions and a generic hypersonic propulsive nozzle evaluated at more realistic on design conditions. A combination of Van Leer flux-vector splitting and Roe flux-difference splitting finite volume computational algorithms were used to solve the unsteady two-dimensional Navier-Stokes equations based on planar, laminar flow, perfect gas equation of state assumptions. For the low speed off-design cases analyzed, gas generator effects on nozzle …

Nonlinear Finite Element Analysis Of Laminated Composite Beams Subjected To Harmonic Excitations Using A 20 Dof Beam Element, Mansour Nosrati Kenareh

Master's Theses - Daytona Beach

The purpose of this thesis is to study the nonlinear analysis of antisymmetrically laminated composite beams including shear deformation subjected to harmonic excitation, using a 20-degree of freedom finite element beam. The beam has 10 degrees of freedom at each node: The axial displacements, the transverse deflection due to bending and transverse shear, the twisting angle, the in-plane shear rotation, and their derivatives along the axial direction. In this study, the effect of different parameters such as damping, shear deformation and different edge conditions on the steady-state frequency-responce will be investigated. The analysis was based on the use of finite …

Nonlinear Forced Vibration Of An Unsymmetrically Laminated Composite Beam, Marie Helene Pompei

Master's Theses - Daytona Beach

The purpose of this thesis is to study the nonlinear forced vibration of an unsymmetrically laminated composite beam. Two cases are considered: unsymmetrical angle-ply and unsymmetrical cross-ply composite beams. The nonlinear governing partial differential equations of motion are obtained by taking into account the von-Karman geometrical nonlinearity. These equations are transformed into nonlinear ODE (Ordinary Differential Equations) by means of the Galerkin method. For both cases the forced Duffing equation was obtained. It is to be noted that only for the unsymmetrical cross-ply laminate simply-supported case are both quadratic and cubic nonlinearities present. The resulting equations for both cases are …

Neural Network Detection Of Fatigue Crack Growth In Riveted Joints Using Acoustic Emission, Adriano F. De Almeida

Master's Theses - Daytona Beach

The purpose of this research was to demonstrate the capability of neural networks to discriminate between individual acoustic emission (AE) signals originating from crack growth and rivet rubbing (fretting) in aluminum lap joints. AE waveforms were recorded during tensile fatigue cycling of six notched and riveted 7075-T6 specimens using a broadband piezoelectric transducer and a computer interfaced oscilloscope. The source of 1,311 signals was identified based on triggering logic, amplitude relationships, and time of arrival data collected from the broad-band transducer and three additional 300 Hz resonant transducers bonded to the specimens. The power spectrum of each waveform was calculated …

The Effects Of Channel Curvature And Protusion Height On Nucleate Boiling And The Critical Heat Flux Of A Simulated Electronic Chip, John E. Leland

Office for Research Publications and Presentations

The quest for higher power yet smaller electronics has given rise to the need for very effective cooling of these electronics. Because one of the foremost problems in electronics cooling is achieving high heat flux cooling within small packages while expending minimal pumping power, one focus of this study was to investigate the effects of channel curvature on the CHF. Experimental data were obtained for flow rates of 1-7 m/s, subcoolings of 5-35"C, and radii of curvature of 25.4 and 50.8 mm. A correlation was obtained for these data which provided an excellent fit.

One condition that has been ignored …

An Aerodynamic And Static-Stability Analysis Of The Hypersonic Applied Research Technology (Hart) Missile, Kenneth J. Moran

Theses and Dissertations

The flow about the complete Hypersonic Applied Research Technology (HART) missile is simulated for inviscid, laminar, and turbulent conditions and Mach numbers from 2 to 6. An explicit, second-order-accurate, flux-difference-splitting, algorithm is implemented and employed to solve the Navier-Stokes equations. The formulation models turbulence with the zero-equation, Baldwin-Lomax turbulence model, accounting for pressure-gradient and compressibility effects. The equations are solved using a finite-volume methodology. In the first part of the study, numerical experiments are performed using an infinitely thin-fin approximation. The aerodynamic and static-stability characteristics are investigated to determine if conventional supersonic missile configurations can be flown at Mach numbers …

Three-Dimensional Aerodynamic Shape Optimization Using Discrete Sensitivity Analysis, Gregory Wayne Burgreen

Mechanical & Aerospace Engineering Theses & Dissertations

An aerodynamic shape optimization procedure based on discrete sensitivity analysis is extended to treat three-dimensional geometries. The function of sensitivity analysis is to directly couple computational fluid dynamics (CFD) with numerical optimization techniques, which facilitates the construction of efficient direct-design methods. The development of a practical three-dimensional design procedures entails many challenges, such as: (1) the demand for significant efficiency improvements over current design methods; (2) a general and flexible three-dimensional surface representation; and (3) the efficient solution of very large systems of linear algebraic equations. It is demonstrated that each of these challenges is overcome by: (1) employing fully …

Unsteady Flow Simulations About Moving Boundary Configurations Using Dynamic Domain Decomposition Techniques, Guan-Wei Yen

Mechanical & Aerospace Engineering Theses & Dissertations

A computational method is developed to solve the coupled governing equations of an unsteady flowfield and those of rigid-body dynamics in six degrees-of-freedom (6-DOF). This method is capable of simulating the unsteady flowfields around multiple component configurations with at least one of the components in relative motion with respect to the others. Two of the important phenomena that such analyses can help us to understand are the unsteady aerodynamic interference and the boundary-induced component of such a flowfield. By hybridizing two dynamic domain decomposition techniques, the grid generation task is simplified, the computer memory requirement is reduced, and the governing …

Implementation Of A Multiblock Sensitivity Analysis Method In Numerical Aerodynamic Shape Optimization, James Matthew Lacasse

Mechanical & Aerospace Engineering Theses & Dissertations

A multiblock sensitivity analysis method is applied in a numerical aerodynamic shape optimization technique. The Sensitivity Analysis Domain Decomposition (SADD) scheme which is implemented in this study was developed to reduce the computer memory requirements resulting from the aerodynamic sensitivity analysis equations, Discrete sensitivity analysis offers the ability to compute quasi-analytical derivatives in a more efficient manner than traditional finite-difference methods, which tend to be computationally expensive and prone to inaccuracies.

The direct optimization procedure couples CFD analysis based on the two-dimensional thin-layer Navier-Stokes equations with a gradient-based numerical optimization technique. The linking mechanism is the sensitivity equation derived from …

Flow Simulations About Steady-Complex And Unsteady Moving Configurations Using Structured-Overlapped And Unstructured Grids, James Charles Newman Iii

Mechanical & Aerospace Engineering Theses & Dissertations

The limiting factor in simulating flows past realistic configurations of interest has been the discretization of the physical domain on which the governing equations of fluid flow may be solved. In an attempt to circumvent this problem, many Computational Fluid Dynamic (CFD) methodologies that are based on different grid generation and domain decomposition techniques have been developed. However, due to the costs involved and expertise required, very few comparative studies between these methods have been performed. In the present work, the two CFD methodologies which show the most promise for treating complex three-dimensional configurations as well as unsteady moving boundary …

The Feasibility Of Using Piezoelectric Flap Actuation In The Active Control Of Flutter, Aaron Laws

Opportunities for Undergraduate Research Experience Program (OURE)

Wing flutter is one of the most important and dangerous phenomenon faced by aircraft structural design engineers. Flutter is a self exciting aeroelastic phenomenon in which portions of an aircraft structure begin to oscillate with exponentially growing amplitudes, produced by the changing aerodynamic forces and moments brought about by the deformation of the structure. There exists a characteristic flight speed, known as the flutter speed, where the structure exhibits sustained harmonic motion, ie. zero damping. Below this velocity, the vibration of the structure due to a perturbation will decrease exponentially, while above this velocity, the vibration will increase exponentially, eventually …

Preliminary Efforts Towards The Analysis Of Unsteady Pressure Measurements Around Wing Models In Transonic Flow, Stephen Witherspoon

Opportunities for Undergraduate Research Experience Program (OURE)

A computer code was developed to implement methods of analyzing unsteady pressure measurements acquired from a wing model immersed in transonic flow. The code uses the fast Fourier Transform to identify phase changes and magnitudes of dominant frequencies over time in the unsteady pressure coefficients. The transformed data, as well as the raw data, are graphed and the results explained in detail identifying features depicted in the graphs. Also, the code performs some simple statistical calculations and smoothes the data to remove insignificant noise in the signal, if desired.

Determination Of Flow Quality And Boundary Layer Thickness In Variable Density Wind Tunnel, Marshall Philips

Opportunities for Undergraduate Research Experience Program (OURE)

The purpose of this paper is to measure the velocity profile in the test section of the Variable Density Wind Tunnel (VDWT). The hot wire anemometer is chosen to measure the velocity profile because of its accuracy and its ability to be moved relatively close to the upper and lower surfaces of the wind tunnel. Special attention is paid to the uniformity of flow velocity in the free stream and whether it varies with position in the tunnel. The measurements were taken at two different stations, two different temperatures, and three different speeds.

Results indicate that the velocity profiles are …

Development Of A Launch System For Performance Studies Of Small Aircraft Models, James J. Schneider

Opportunities for Undergraduate Research Experience Program (OURE)

This paper presents a design of a launching system that can be employed for performance studies on small aircraft models. Further the article describes a design and development of an aircraft model for use with the system. initial analysis and testing of the system using the designed aircraft model will be presented.

The Effect Of Spatial Variation Of The Turbulent Prandtl Number And Calculation Methods For Heat Transfer In High Mach Number Flows, Thomas W. Scott

Opportunities for Undergraduate Research Experience Program (OURE)

The effect of using various spatial distributions of the turbulent Prandtl number on the predicted surface heat transfer in the numerical simulation of Mach 4 flat plate flow is studied. The spatial distribution of the turbulent Prandtl number is shown to have a small effect on surface heat transfer, hence suggesting that the standard assumption of a constant turbulent Prandtl number is acceptable for high Mach number boundary layer type flows. In addition, a wall-cell control volume technique for computing heat transfer shows superior predictive capacity across the Reynolds number range when compared to the conventional calculation of surface heat …

Direct Reduced Order Mixed H2/H∞ Control For The Short Take-Off And Landing-Maneuver Technology Demonstrator (Stol-Mtd), William C. Reigelsperger Jr.

Theses and Dissertations

One of the conclusions from the STOL/MTD program was the need for a multivariable method of designing controllers of low order. This research investigated that problem by studying reduced order mixed H₂/H_∞ control theory applied to the STOL Landing configuration which employs both thrust vectoring and the use of a canard. Model matching techniques were used to obtain responses that met handling qualities criteria and reduced pilot workload by decoupling pitch rate and velocity commands. The time responses were found through nonlinear simulation and showed that the full order designs did match the ideal models very well …

A Handling Qualities Investigation Of Conventional, Rate Command- Attitude Hold, And Attitude Command-Attitude Hold Response-Types In The Probe And Drogue Air Refueling Task, Michael J. Taschner

Theses and Dissertations

This investigation examines the suitability of conventional, rate command/attitude hold (RCAH), and attitude command attitude hold (ACAH) response-types for the probe and drogue air refueling task. Data from a 1974 Calspan handling qualities investigation involving conventional response-types in the probe and drogue air refueling task were analyzed using the Bandwidth and STI Dropback criterions. Flight control laws were developed to achieve twelve superaugmented and two conventional configurations. The NT-33A analog variable stability system was used to simulate a relaxed static stability fighter and the NT-33A programmable digital flight control computer simulated the desired response-types. The handling qualities of the fourteen …

A Heuristic Approach To Determining Cargo Flow And Scheduling For Air Mobility Command's Channel Cargo System, John Fitzsimmons Jr., John Walker

Theses and Dissertations

This research investigated a heuristic approach to schedule aircraft for the channel cargo system of the Unit States Air Forces Air Mobility Command AMC. Given cargo frequency of visit requirements, a fleet of aircraft, and possible routes, the objective of this research was to develop, implement, and test an iterative procedure to efficiently schedule and load aircraft in order to maximize the flow of cargo through the channel cargo system. Once a level of flow was established, attempts were made to minimize cost in terms of cumulative weighted time-in-system CWTIS. A minimum cost flow heuristic, incorporating a successive shortest path …

Optimization Of The Air Apportionment In A Tac Thunder Scenario Using Response Surface Methodology, Steven L. Forsythe

Theses and Dissertations

To effectively compare different sets of available aircraft, it is necessary to find the apportionment that maximizes the effectiveness of each set of aircraft. This research effort uses an unclassified TAC THUNDER scenario to show how an analyst can use response surface methodology RSM techniques to estimate the relationship between aircraft apportionment and campaign outcomes. The optimal apportionments for one phase of a hypothetical conflict was found by using a steepest-gradient search of the constrained response surfaces. The results are illustrated by illuminating charts showing the various relationships between the number of aircraft in the theater and measures of effectiveness …

Compression Of A Radar Track Of A Near Earth Satellite Into An Earth Centered Inertial State Vector Using Least Squares Differential Correction, Garry L. Hall

Theses and Dissertations

This study investigated the use of a least squares differential corrector to compress the information contained in a single radar track of a Near Earth satellite into a six element, Earth Centered Inertial state vector and associated covariance matrix. Observations were generated using a truth model program based on two body, J2 geopotential, and atmospheric drag dynamics and consisted of simulated range, azimuth and elevation. Random Gaussian noise was added to the data to simulate real world random errors. The orbital dynamics used in the estimator consisted of two body and J2 geopotential effects which were approximated using a Taylor …

A Shock Tube Study Of Aerodynamic Heating Of Gaps In A Cylinder Subjected To Supersonic Cross Flow, Douglas D. High

Theses and Dissertations

The effects of localized aerodynamic heating in cylinder expansion gaps positioned in cross flow were investigated in a shock tube. For this study, Mach number and Reynolds number were varied from 1.04 to 1.38 and 5 x 105 to 9 x 105, respectively. The cylinder was instrumented with quick response time thermocouples positioned on the surface of the cylinder, the wall of the gap, and the gap floor. Gap aspect ratios varied from 1.23 to 3.69. Pressure gauges were used to measure wave shock speeds, pressure ratios, and transient pressure conditions. Surface temperatures were measured and converted to heat fluxes …

Resonance Capture In Unbalanced Dual-Spin Spacecraft, Raymond Tsui

Theses and Dissertations

This study examines the spinup dynamics of dual-spin spacecraft having an imbalanced rotor. Of particular interest is a phenomenon called 'resonance capture' during which the spinup motor torque induces uncontrolled growth of nutation. A captured spacecraft tumbles end-over-end, while an escaped spacecraft experiences little nutation growth. The conditions which lead to both state are analyzed. A set of criteria based on the spacecraft's kinetic energy at the of spinup is used to determine whether or not it has been captured. To calculate the final energies against which these criteria are compared, a set of nondimensional equations of motion are numerically …

Free Vibrations Of A Piezoelectric Body, J. S. Yang, R. C. Batra

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We present a systematic analysis of the eigenvalue problem associated with free vibrations of a finite piezoelectric body. The analysis is based on an abstract formulation of the three-dimensional theory of piezoelectricity. A series of fundamental properties of free vibrations of a piezoelectric body are proved concisely. The problem of free vibrations of a piezoelectric plate governed by the two-dimensional plate equations due to Mindlin is treated in a similar manner. © 1994 Kluwer Academic Publishers.

A Genetic Algorithm Approach To Automating Satellite Range Scheduling, Donald A. Parish

Theses and Dissertations

Satellite range scheduling involves scheduling satellite supports in which a satellite and a specific remote tracking station communicate with each other within a specified time window. As the number of satellite supports continue to increase, more pressure is placed on the current manual system to generate schedules efficiently. Previous research efforts focused on heuristic and mixed-integer programming approaches which may not produce the best results. The objective of this research was to determine if a genetic algorithm approach to automating the generation of 24 hour schedules was competitive with other methods. The goal was to schedule as many supports as …

Interactive Learning: The Casewriting Method As An Entire Semester Course For Higher Education Teacher's Manual, Brent D. Bowen, Rebecca K. Lutte, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 94-2

This guide explains the reasons for employing the case method as a tool in the academic discipline of aviation. It promotes the use of case writing as a unique opportunity to derive even further benefits from case analysis. The benefits to students of using case writing as a learning strategy include a focus on the strategy of a real situation; development of an ownership interest; and development of reasoning, decision making, judgment, group dynamics, formal written and oral communication ability, and organizational skills. This is a teacher's guide that includes the course syllabus, schedule and practical tips …

Interactive Learning: The Casewriting Method As An Entire Semester Course For Higher Education, Brent D. Bowen, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 94-1

This guide explains for reasons for employing the case method as a tool in the academic discipline of aviation. It promotes the use of case writing as a unique opportunity to derive even further benefits from case analysis. The benefits to students of using case writing as a learning strategy include a focus on the strategy of a real situation; development of an ownership interest; and development of reasoning, decision making, judgement, group dynamic, formal written and oral communication ability, and organizational skills. Issues related to computerization, research, and internalization are also addressed. Among the topics covered …

Finite Element Analysis For Nonlinear Flutter Suppression Of Composite Panels At Elevated Temperatures Using Piezoelectric Materials, Run Chen Zhou

Mechanical & Aerospace Engineering Theses & Dissertations

Nonlinear coupled finite element equations of motion are derived for composite panels with embedded piezoelectric layers subjected to aerodynamic, thermal loads and applied electric fields. The nonlinear equations of motion describe the coupling between a structure and an electrical network through the piezoelectric effect. The von Karman large-deflection strain-displacement relations, quasi-steady first-order piston theory aerodynamics, quasi-steady thermal stress theory and linear piezoelectricity theory are used to formulate the nonlinear coupled panel flutter finite element equations of motion in nodal displacements. The governing equations, which are referred to actuator and sensor equations, form a basis for piezoelectric actuation and sensing. Following …