Engineering Commons^™

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 …

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.

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 …

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 …

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 …

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 …

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 …

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 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 …

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 …

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 …

Experiences In The Integration Of Design Across The Mechanical Engineering Curriculum, Ashok Midha, J. M. Starkey, D. P. Dewitt, R. W. Fox

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Faculty of the School of Mechanical Engineering at Purdue University have effected a major change in the Purdue Mechanical Engineering program by integrating design throughout the curriculum. In doing so, a significant level of faculty interaction has been achieved as well. The goals of the curriculum revision are: (1) to improve student skills in how to solve open-ended design problems, (2) to reduce the core of the curriculum to allow flexibility in course selection, and allow time for solving design problems, (3) to improve student skills in team work and communications, and (4) to improve student skills in using …

Use Of Hopfield Neural Networks In Optimal Guidance, S. N. Balakrishnan, James Edward Steck

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A Hopfield neural network architecture is developed to solve the optimal control problem for homing missile guidance. A linear quadratic optimal control problem is formulated in the form of an efficient parallel computing device known as a Hopfield neural network. Convergence of the Hopfield network is analyzed from a theoretical perspective, showing that the network, as a dynamical system approaches a unique fixed point which is the solution to the optimal control problem at any instant during the missile pursuit. Several target-intercept scenarios are provided to demonstrate the use of the recurrent feedback neural net formulation.

Buckling Of A Coating Bonded To A Round Bar Subjected To Axial Extension. Mech. Mater. 15 (1993) 131-138, C. W. Bert, Victor Birman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

Automation Of Formation Flight Control, Vincent P. Reyna

Theses and Dissertations

The research contained in this thesis explores the concepts of Automated Formation Flight Control documented in three previous AFIT theses. The generic formation analyzed consists of a Leader and Wingman, with the Wingman referencing its maneuvers off of Leader maneuvers. Specifically, planar formation flight control concerning only heading and velocity changes is considered. Next, the vertical separation constraint is relaxed to allow wing maneuvers outside of the flight plane of the lead in order to minimize the energy expended by the wing in a maneuver. Analysis of the two forms of formation flight control investigated in this thesis reveals the …

Numerical Simulation Of The Nonlinear Response Of Composite Plates Under Combined Thermal And Acoustic Loading, Jayashree Moorthy

Mechanical & Aerospace Engineering Theses & Dissertations

A time-domain study of the random response of a laminated plate subjected to combined acoustic and thermal loads is carried out. The features of this problem also include given uniform static inplane forces. The formulation takes into consideration a possible initial imperfection in the flatness of the plate. High decibel sound pressure levels along with high thermal gradients across thickness drive the plate response into nonlinear regimes. This calls for the analysis to use von Karman large deflection strain-displacement relationships. A finite element model that combines the von Karman strains with the first-order shear deformation plate theory is developed. The …

Vibration Control With Piezoelectric Actuation Applied To Nonlinear Panel Flutter Suppression, Zhihong Lai

Mechanical & Aerospace Engineering Theses & Dissertations

Panel flutter is a large-deflection limit-cycle motion excited by the airflow, which is only on one side of a panel. The objective of this research is to analytically study the panel flutter limit-cycle suppression using nonlinear vibration control techniques with piezoelectric actuation. It is well known that piezoelectric materials are characterized by their ability to produce an electrical charge when subjected to a mechanical strain. The converse piezoelectric effect can be utilized to actuate a panel by applying an electrical field. Piezoelectric actuators are driven by feedback controllers, and control the panel dynamics. For a simply supported panel with piezoelectric …

Multigrid Acceleration Of Time-Dependent Solutions Of Navier-Stokes Equations, Sarafa Oladele Ibraheem

Mechanical & Aerospace Engineering Theses & Dissertations

Recent progress in Computational Fluid Dynamics is encouraging scientists to look at fine details of flow physics of problems in which natural unsteady phenomena have hitherto been neglected. The acceleration methods that have proven very successful in steady state computations can be explored for time dependent computations. In this work, an efficient multigrid methods is developed to solve the time-dependent Euler and Navier-Stokes equations. The Beam-Warming ADI method is used as the base algorithm for time stepping calculations. Application of the developed algorithm proved very efficient in selected steady and unsteady test problems. For instance, the inherent unsteadiness present in …

Optimal Design Of Laminated Plates And Shells, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Designing structures made out of composite materials represents a challenging task, since not only the thickness of the element must be determined to satisfy the constraints of the problem, but, in addition, the number of plies in the laminate and their relative orientation must also be selected. Because of their strong anisotropy, a careful selection of lay-up is required to make the best use of the capabilities of the material. In this article the optimum design of laminated plates and shells subjected to constraints on strength, stiffness, buckling loads, and fundamental natural frequencies are examined. © 1994.

On The Propagation Of A Shear Band In A Steel Tube, R. C. Batra, Xiangtong Zhang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Marchand and Duffy tested thin-walled steel tubes in a split Hopkinson torsion bar at a nominal strain-rate of approximately 1600/s and could not determine conclusively whether a shear band initiating at a point in the tube propagated around the circumference in one direction or in both directions. They estimated the speed of propagation to be 520 m/s in the former case and 260 m/s in the latter. Here we simulate their test numerically and find that the shear band propagates in both directions around the circumference of the tube. When the tube is twisted at a nominal strain-rate of 5000/s, …

Approximate Analytical Guidance Schemes For Homing Missiles, S. N. Balakrishnan, Donald T. Stansbery

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Closed form solutions for the guidance laws are developed using modern control techniques. The resulting two-point boundary value problem is solved through the use of the state transition matrix of the intercept dynamics. Results are presented in terms of a design parameter.

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 …

Impact On Laminated Composites: Recent Advances, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Impact damage in structures made out of composite materials is a major concern since such damage can be introduced during the life of the structure, and its mechanical properties can be drastically reduced as a result. In a previous review of the literature on impact on composite materials, this author considered 285 published before 1989. In this article over 300 articles most of which appeared after 1989 are reviewed. These figures indicate that this is a very active area of research, and the present paper seeks to present a comprehensive view of the latest developments. Taken together, these two reviews …

On The Interface Stability Of A Neck Propagating In A Sheet Reinforced With Shape-Memory Fibers, C. Q. Ru, R. C. Batra

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We propose a simple model of necking in a sheet reinforced with straight fibers made of a shape-memory alloy and examine conditions under which the interface between the necked and the unnecked region is morphologically stable. We use the Mullins and Sekerka (1963, J. Appl. Phys. 34, 323-330; 1964, J. Appl. Phys. 35, 444-450) method, established for studying the stability of a moving interface in a solidification problem, to investigate the interface stability of a propagating neck. It is found that the moving straight interface is morphologically stable for several typical cases even in the absence of surface-tension effects, and …

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 …

Comparison Of Air Traffic Control Candidate Ability With Simulator-Based Training Measures, Lawrence A. Tomaskovic

Master's Theses - Daytona Beach

The purpose of this study was to determine if the utilization of an experimental computer-based selection test battery would aid in the prediction of a candidate's performance when using an air traffic control computer-based simulation program. Each candidate completed the selection test battery, and then received air traffic control instruction using the air traffic control simulation program incorporated in the TRACON/Pro™ simulator system. The selection test battery results were correlated with the subsequent simulator scoring results.

The Effect Of Active And Passive Control On Air Traffic Controller Dynamic Memory, Esa M. Rantanen

Master's Theses - Daytona Beach

The purpose of this study was to investigate the effect of automated and passive control on air traffic controller dynamic memory. The study consisted of two experiments, each involving a realistic ATC scenario for radar approach control with a mix of arriving and departing traffic. In Experiment I, the subjects performed manual control of the traffic while, in Experiment II, the scenario was highly automated and the subjects were tasked with only monitoring the situation. The dynamic memory performance was measured by interrupting the scenario and having the subjects recall the traffic situation at the moment of simulation interruption. The …

An Approximate Solution For The Spinup Dynamics Of Near Axisymmetric Axial Gyrostats Using The Method Of Multiple Scales, Stewart J. Kowall

Theses and Dissertations

Approximate solutions for the spinup of a near axisymmetric gyrostat are derived using the straightforward expansion method and the method of multiple scales. Two method of multiple scale solutions are presented. The first is derived using cartesian coordinates while the second is derived using cylindrical coordinates. The multiple scales solutions are compared to numerically integrated results for oblate and prolate configurations. A comparison for flat spin recovery is also accomplished. Excellent results are obtained for oblate configurations. Trajectory separatrix crossings hindered the results for prolate configurations and flat spin recoveries.