Engineering Commons^™

Stanford Space Systems Development Program, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Stanford Space Systems Development Program" from April 21, 1998.

A Study Of The Volume Of Fluid Method For Moving Boundary Problems, Marianne Francois

Master's Theses - Daytona Beach

Moving boundary problems are often encountered in engineering and science. One of the methods to solve such problems numerically is the volume of fluid (VOF) method. The VOF method uses an additional field variable/to track the interface using the Eulerian fixed grid. In this work, the VOF method is combined with the Continuum surface force model. The governing flow equations for Newtonian fluids in incompressible flow in two dimensions are solved using the pressure-based algorithm. A linear interface reconstruction algorithm is developed and improved by interpolations. In order to validate the code, the problem of the convection of a two-fluid …

Reduction Of Thermal Deflection And Random Response Of Composite Structures With Embedded Shape Memory Alloy At Elevated Temperature, Zhiwei Zhong

Mechanical & Aerospace Engineering Theses & Dissertations

A feasibility study on the reduction of thermal deflection and random response of the composite structures using shape memory alloys (SMA) at elevated temperatures is presented in this dissertation. The characteristics of SMA are introduced and the structural problems, static and dynamic, of SMA fiber reinforced composites are investigated. The stress-strain relations are developed for a composite lamina with embedded SMA fibers. The finite element system equations including shape memory effect are derived. A consistent two-step solution procedure is developed for solving the static and dynamic problems of composite structures with embedded SMA fibers subjected to combined acoustic and thermal …

Analysis And Testing Of Plates With Piezoelectric Sensors And Actuators, Jeffrey S. Bevan

Mechanical & Aerospace Engineering Faculty Publications

Piezoelectric material inherently possesses coupling between electrostatics and structural dynamics. Utilizing linear piezoelectric theory results in an intrinsically coupled pair of piezoelectric constitutive equations. One equation describes the direct piezoelectric effect where strains produce an electric field and the other describes the converse effect where an applied electrical field produces strain. The purpose of this study is to compare finite element analysis and experiments of a thin plate with bonded piezoelectric material. Since an isotropic plate in combination with a thin piezoelectric layer constitutes a special case of a laminated composite, the classical laminated plate theory is used in the …

The Airline Quality Rating 1998, Brent Bowen, Dean Headley, Uno Aviation Institute

Faculty Books and Monographs

UNOAI Report 98-1

The Airline Quality Rating (AQR) was developed and first announced in early 1991 as an objective method of comparing airline performance on combined multiple factors important to consumers. Development history and calculation details for the AQR rating system are detailed in The Airline Quality Rating issued in April, 1991, by the National Institute for Aviation Research at Wichita State University. This current report, Airline Quality Rating 1998, contains monthly Airline Quality Rating scores for 1997. Additional copies are available by contacting Wichita State University or the University of Nebraska at Omaha.

The Airline Quality Rating 1998 is …

The Design And Testing Of An Inlet-Airfoil For A High Altitude Remotely Piloted Aircraft, Preston Bradley Martin

Mechanical & Aerospace Engineering Theses & Dissertations

The following work describes and validates a methodology for the aerodynamic design of a low drag, efficient inlet-airfoil to be used on the cooling installations of a high altitude remotely piloted aircraft. Owing to the primary aircraft design requirement of subsonic endurance at high altitude (85,000 ft), the flight conditions present an aerodynamically unfavorable combination of low chord Reynolds number (500,000) and high subsonic Mach number (0.5). At this flight condition, the inlet-airfoil must meet the heat exchanger cooling flow requirements while maintaining the aerodynamic performance of the airfoil. As a result, the design method is closely coupled with not …

Experimental Geometry Optimization Techniques For Multi-Element Airfoils, Drew Landman

Mechanical & Aerospace Engineering Theses & Dissertations

A study is reported on geometry optimization techniques for high-lift airfoils. A modern three-element airfoil model with a remotely actuated flap was designed, tested, and used in wind tunnel experiments to investigate optimum flap positioning based on lift. All the results presented were obtained in the Old Dominion University low-speed wind tunnel. Detailed results for lift coefficient versus flap vertical and horizontal position are presented for two airfoil angles-of-attack: 8 and 14 degrees. Three automated optimization simulations, the method of steepest ascent and two variants of the sequential simplex method, were demonstrated using experimental data. An on-line optimizer was demonstrated …

An Evaluation Of Frequency Domain Ensemble Averaging To Improve Aircraft Stability Derivative Estimation, Lawrence M. Hoffman

Theses and Dissertations

This research evaluated a process to improve aircraft stability derivative estimation results. The Have Derivatives process used overlap ensemble averaging in the frequency domain to minimize noise on the original time domain signals. The process estimated average complex frequency response functions that were then transformed back into the time domain as a set of discrete pulse responses with far less noise than the original signals. These clean signals were used in a parameter estimation program to estimate better stability derivatives than were estimated with the original noisy signals. Both simulation and flight test data were used to study the effects …

Optimizing The Efficiency Of A Multi-Stage Axial-Flow Compressor: An Application Of Stage-Wise Optimization, Shawn A. Miller

Theses and Dissertations

The development of jet engines has become an integral part of maintaining air superiority. In order to achieve the most advanced engine, research has turned to traditional optimization methods to aid in creating new engine designs. To develop simplified mathematical models representative of the engine, the engine can be separated into its components. A jet engine has three major elements, the compressor, combustion chamber and turbine. This research attempts to make an initial analysis of a two stage compressor to determine values of blade angles and spacing to chord ratios for both stages that produce the highest possible efficiency for …

Improved Mathematical Modeling For Gps Based Navigation, Salvatore Nardi

Theses and Dissertations

This thesis is concerned with the development of new closed form GPS position determination algorithms that work in the presence of pseudorange measurement noise. The mathematical derivation of two closed form algorithms, based on stochastic modeling and estimation techniques, is presented. The algorithms provide an estimate of the GPS solution parameters (viz., the user position and the user clock bias) as well as the estimation error covariance. The experimental results are analyzed by comparison to the baseline results from the conventional Iterative Least Squares (ILS) algorithm. In typical GPS scenarios, the closed form algorithms are extremely sensitive to noise, making …

Effect Of High Free Stream Turbulence On Film Cooling Using Double Row Of 30° Slant-Hole Injectors, Lilith I. Sorensen

Theses and Dissertations

In this study free stream turbulence levels from 7.3% to 17.8% are applied to film cooling over a flat plate with two rows of 30° slant holes using a wall jet as the main stream air supply and source of turbulence. Blowing ratios are varied from 0.25 to 2.0 and free stream velocities at injection range from 10 m/s to 85 m/s. A constant density ratio of 1.07 is kept throughout the experiment. Results show that for different magnitudes of blowing ratio free stream turbulence has a different influence on effectiveness. At the forward stations, where blow off was present …

A Variable-Complexity Modeling Approach To Scramjet Fuel Injection Array Design Optimization, Michael D. Payne

Theses and Dissertations

The analysis of fuel air mixing in a scramjet is often accomplished either with Computational Fluid Dynamics (CFD) algorithms or through experimental research. These approaches, while accurate and reliable, are extremely expensive and thus not well suited for use with conventional design optimization methods. In this investigation, Variable Complexity Modeling (VCM) is used to significantly reduce the number of complex, expensive analyses required to optimize the design of a scramjet fuel injection array. A design problem formulation for a lateral transverse injection array is developed and a VCM approach to design optimization is conducted in two stages. Initially, a simplified …

Damage Detection Using Pattern Classifiers, Eric D. Swenson

Theses and Dissertations

The research focused on developing and tuning finite element models to train pattern classifiers to detect and locate damage in a real structure. The research was broken into three distinct phases: finite element (FE) model development, FE model tuning, and pattern classifier training and testing. In the finite element development phase, a low order FE model called the baseline model and a high order model called the stiff model were created. In the FE model tuning phase, these FE models were tuned using measured Frequency Response Functions (FRFs), and the results were compared with previous research in which tuning was …

The Influence Of Surface Roughness On Supersonic High Reynolds Number Turbulent Boundary Layer Flow, Robert M. Latin

Theses and Dissertations

A comprehensive study of rough-wall high speed (M=2.9) high Reynolds number (R_e/m = 1.9 x 10⁷) turbulent boundary layer flow was performed consisting of experimental, analytical, and numerical methods. Six wall topologies consisting of a smooth and five rough surfaces (two and three dimensional machined roughness plates; and 80, 36, and 20 grit sand-grain roughened plates) were studied. A confocal laser scan microscope was used to measure the topography of the sand grain roughnesses. The experimental measurement techniques included a convention Pitot pressure probe, laser Doppler velocimetry, hot wire anemometry; color schlieren and laser …

Analysis Of Turbulence Models As Applied To Two- And Three-Dimensional Injection Flows, Clarence R. Chenault

Theses and Dissertations

A steady state solution of the full, three dimensional Favre averaged Navier Stokes equations, coupled with a second order Reynolds stress turbulence model (RSTM) and an eddy viscosity model were used to numerically simulate oblique injection into supersonic flow. Numerical results were compared to experimental data and the turbulence models were evaluated for accurate prediction of thermomechanical mean flow variables, Reynolds stresses, flowfield shock structure and boundary layer phenomena. The RSTM simulation resulted in physically consistent and accurate predictions for the mean flow and turbulent quantities. Simulations with the eddy viscosity model resulted in non-physical and inconsistent turbulence predictions. RSTM …

Flight Test And Handling Qualities Analysis Of A Longitudinal Flight Control System Using Multiobjective Techniques, John R. Anderson

Theses and Dissertations

This thesis addresses the application of optimal, multiobjective control theory control theory to flight control design for the approach and landing phase of flight. Five flight control systems were designed using classical, H2, H infinity, and Mixed H2/H infinity methods. The MATLAB™ MUTOOLS™ and AFIT MXTOOLS toolboxes were used to produce the optimal, multiobjective designs. These designs were implemented for flight test on the Calspan VSS I Learjet, simulating the unstable longitudinal dynamics of an F-16 type aircraft. A limited handling qualities investigation was performed. Model following was used in the design phase to meet handling qualities specifications. The designs …

A Model For Calculating Acoustic Gravity Wave Energy And Momentum Flux In The Mesosphere From Oh Airglow, Gary R. Swenson, Alan Z. Liu

Physical Sciences - Daytona Beach

Acoustic gravity and tidal waves propagating in the mesosphere/lower thermosphere (80-110 km) perturb the airglow layer intensities. The OH airglow has recently been modeled to determine the relationship between the relative perturbed atmospheric density and temperature (ρ’/ ρ, T’/T) to the OH intensity ( I’_OH/I_OH ) at the OH emission altitudes [Swenson and Gardner, 1997]. A model is presented here which relates wave perturbed OH airglow to the wave energy and momentum flux as they propagate through the emission layer. The model is dependent on the wave horizontal and vertical wavelengths (or phase speed as related through …

The Restoration Of A Wwii Avenger Provides Projects For Wpi Students, Donald N. Zwiep, William W. Durgin, Nathan H. Mayo

Office of the Provost Scholarship

In 1970 WPI completely revised its traditional approach to engineering education. The resulting program, the WPI Plan, emphasized the use of projects as a distinctive process for achieving educational goals. Every student, as a degree requirement, had to successfully complete two major projects: one in a student's major field, the Major Qualifying Project (MQP) and the second, the Interactive Qualifying Project (IQP), which related science and technology to societal issues.

The IQP's related to the restoration of the WWII Avenger at Mayocraft, Inc. for the Collings Foundation in Stow, Massachusetts enabled the students working with the authors as advisors to …

Battery-Operated Atomic Force Microscope, Burford J. Furman, J. Christman, M. Kearny, F. Wojcik, M. Tortonese

Faculty Publications, Mechanical Engineering

The design of a battery-operated atomic force microscope (AFM) using a piezoresistive cantilever is described. The AFM is designed so that all power to drive the scanning tube and detection electronics comes from a self-contained battery. The prototype AFM uses a 6 V, Ni–Cd, camcorder battery, however, any battery that supplies between 6 and 12 V may be used. Scanner control and data acquisition are implemented using commercially available software running on an external computer. The prototype AFM achieves a scan area of 53 by 53 μm, consumes 1.8 W of power, and can scan continuously for about 7 h …

A Class Of Modified Hopfield Networks For Control Of Linear And Nonlinear Systems, Jie Shen, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper presents a class of modified Hopfield neural networks (MHNN) and their use in solving linear and nonlinear control problems. This class of networks consists of parallel recurrent networks which have variable dimensions that can be changed to fit the problems under consideration. It has a structure to implement an inverse transformation that is essential for embedding optimal control gain sequences. Equilibrium solutions are discussed. Numerical results for a motivating aircraft control problem (linear) are presented. Furthermore, we formulate the state-dependent Riccati equation method (SDRE) for a class of nonlinear dynamical system and show how MHNN provides the solution. …

Cell Mapping Based Fuzzy Control Of Car Parking, Tea-Quin Kim, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper describes the development of a near-optimal fuzzy controller for maneuvering a car in a parking lot. To generate the rules of the fuzzy controller, a cell mapping method is utilized to systematically generate near-optimal trajectories for all possible initial states in the parking lot. Based on the input-output relations of these trajectories, which represent the states and controls of the corresponding cells, a set of fuzzy rules are generated automatically. In order to result in a small number of fuzzy rules from the large amount of numerical information generated by cell mapping, grouping of trajectories is proposed and …

An Mdo-Compatible Method For Robust Design Of Vehicles, Systems, And Components, Leslie D. Liaw, Richard I. Devries, Donald L. Cronin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A CAE simulation process was developed to quantify the variability of vehicle attributes such as safety, durability, vehicle dynamics, NVH and weight. The process was integrated with the Ford multi-function optimization (MFO) tool — MOVE (Multi-Function Optimization Visualization Environments) in order to facilitate the robust design of vehicles, systems and components. The statistics of vehicle attribute responses are computed given the statistics of the design parameters. The response surface approximation was used to simplify the input and output relationships. A variety of statistical distributions can be selected to match the statistics of the design parameters which are continuous or discrete. …

Robustness Analysis Of Hopfield And Modified Hopfield Neural Networks In Time Domain, Jie Shen, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A variant of the Hopfield network, called the modified Hopfield network is formulated. This network which consists of two mutually recurrent networks has more free parameters than the well-known Hopfield network. Stability analysis of this network is presented. The analysis is carried out in the time domain with an application of the Lyapunov method and robust control Lyapunov function. The current flow in the network is treated as a "control". This "controller" is shown to guarantee "a practically stabilizing control". Analysis of the Hopfield network is also included for completion.

Emerald: A Low-Cost Spacecraft Mission For Validating Formation Flying Technologies, Robert J. Twiggs, Jonathan How, Christopher Kitts

Robert "Bob" Twiggs STEM Education Collection

A published report by Bob Twiggs, Jonathan How, and Christopher Kitts titled "EMERALD: A Low-Cost Spacecraft Mission for Validating Formation Flying Technologies" from 1998.

Nanosatellite Program – A Challenge To Amsat For Collaboration To Use The Amateur Bands, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A report published by Professor Bob Twiggs titled "Nanosatellite Program – A Challenge to AMSAT for Collaboration to Use the Amateur Bands" from 1998.

The Effect Of A Baffle On Acoustic Radiation Directivity, Walter Eversman, Indranil Danda Roy

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An investigation is made of the effect of an artificial baffle introduced in Finite Element modeling of acoustic radiation from turbofan inlets. The purpose of the baffle is to limit the extent of the computational domain in order to maximize the efficiency of the scheme. However, the possibility exists that the baffle, if improperly oriented, will generate spurious reflections which interfere with the true radiated acoustic field. A generic example of a turbofan inlet, including typical geometry and non-uniform potential flow in and around the nacelle, is modeled with a baffle as typically introduced limiting the angular extent of the …

Aerodynamic Interference For Hypersonic Missiles At Low Angle Of Attack, Harlan F. Nelson, Derek G. Hillstrom

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A Euler code is used to predict the flow field over a hypersonic missile and to determine the carryover factors KW(B), fin lift in the presence of the body, and KB(W), lift produced by the body in the presence of the fins. The missile is assumed to have cruciform, delta fins in the + orientation and an aspect ratio of 1.529. Results are presented as a function of fin span at Mach 6, 8, and 10, for a 2-deg angle of attack. Two ratios of specific heats, 1.4 and 1.3, are considered to partially account for vibrational excitation effects. Both …

An Integrated Approach To Determining The Sequence Of Machining Operations For Prismatic Parts With Interacting Features, Alan C. Lin, Shou Yee Lin, Das Diganta, Wen F. Lu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper proposed a framework for integrating artificial intelligence (AI) techniques and mechanistic models in the task of generating process plans for prismatic parts. The main issue of process planning addressed in this paper is the determination of the operation sequence for mechanical parts containing interacting features where machining of one feature might adversely affect the surface quality of other features. The informed graph-search strategy in AI is used to achieve the function of operation sequence planning. The search graph is built by considering alternative machining operations in converting a blank stock into the final part configuration. Several heuristic functions …

Placement Of Piezoelectric Actuators For Active Control Of Vibration Using Modal Parameters, Xuegeng Zhu

Mechanical & Aerospace Engineering Theses & Dissertations

An equation is derived to model the piezoelectric actuators incorporation with flexible structures. This equation permits the comparison of the performance indices over the entire structure for a piezoelectric actuator with constant area, which is unachievable if the Finite Element Method is used for complicated structures.

An index has been developed for placement of piezoelectric actuator for control of vibration of a flexible structure. This index is derived from the definition of H2norm. Computation of the proposed index requires only the natural frequencies and corresponding mode shapes of the structures of interest. The method is well suited to large …

Printer Carriage Motion Control Experiment, Burford Furman

Faculty Research, Scholarly, and Creative Activity

No abstract provided.