Engineering Commons^™

Computation Of Planar Store Trajectories Using An Adaptive Grid Procedure, William D. Hack

Theses and Dissertations

The objective of this research was to compare a quasi-analytical, potential flow/three-degree-of-freedom model to an implicit-Euler algorithm for the calculation of store trajectories. The implicity algorithm uses a cell- centered, finite-volume, spatial discretization applied to the Euler equations, written in time-dependent, curvilinear-coordinates. A flux-differencing Roe scheme is employed to find the split-fluxes and the Steger/Warming flux-vector method is used to calculate the flux-Jacobians. The potential flow and implicit- Euler algorithm are combined with a three-degree-of-freedom algorithm to evaluate the planar, freefall trajectories of a simple store shape. The research uses two different grid-modification techniques in the implicit algorithm evaluation. Data …

Tensile Strength Characterization Of A Metal Matrix Composite With Circular Holes, Jeffrey Rattray

Theses and Dissertations

Static tensile testing conducted at room temperature and 650 C shows notch sensitivity for a quasi-isotropic lay-up of a titanium alloy metal matrix composite. The specific material used was SCS-6/Beta 21S. Some unnotched specimens were tested and then the diameter-to-width ratio was varied from 0.1 to 0.4. The room temperature unnotched strength is 840 MPa, and the strength falls to less than half this value at 650 C. The off-axis plies of the (0, + or - 45, 90)s lay-up exhibit debonding of the fibers from the matrix at only ten percent of failure stress. This debonding is shown with …

The Use Of A Higher Order Kinematic Relationship On The Analysis Of Cylindrical Composite Panels, Kathleen V. Tighe

Theses and Dissertations

An analytical study was performed to determine the critical buckling loads and natural frequencies for composite cylindrical shells, including transverse shear effects and constant through the thickness direct strain ε_z. A linearized form of Sanders shell equations are derived, including a parabolic transverse shear strain distribution. Higher order laminate constitutive relations are developed. Hamilton's Principle is applied to derive five partial differential equations of motion and the associated boundary conditions, which are then solved using the Galerkin technique. Ply layups of (0/90), (45/-45), and (0/45/-45/90) were investigated under three boundary conditions, simply supported, clamped, and a combination simple- …

A Comparison Of Fractional Order Time Derivative Models Of The Viscoelastic Stress Relations In Thermorheologically Complex Materials, Victor B. Chambers

Theses and Dissertations

The purpose of this thesis was to examine the viscoelastic behavior of thermorheologically complex materials, a typical example of which is a soft, rubbery material. Materials such as these are very useful in damping vibrations in structures, but the relaxation moduli of these materials change significantly with temperature and frequency. In the case of space structures applications where temperatures vary greatly and a stable platform is necessary, a method to predict this changing modulus is needed. The original approach was to validate a previously developed viscoelastic model, but the task expanded to include extending the model to materials with two …

Application Of Finite Element Modeling And Analysis To The Design Of Positive Pressure Oxygen Masks, Bruce H. Bitterman

Theses and Dissertations

This study investigated tools and techniques for performing finite element analysis of the MBU-20/P pilot's oxygen mask. The problem which was investigated was the fit of the mask to the face at Positive Pressure Breathing (PPB) pressures. Deformed geometry of the mask and reaction forces on the face were calculated to provide a measure of the fit. The MBU-20/P mask was first digitized by 3-D digitizer. A computer program was written to translate the digitized coordinate data to a finite element format for two commercial packages. The packages targeted were SDRC I-DEAS and PDA PATRAN. Other supplementary programs were written …

Navigation Of A Satellite Cluster With Realistic Dynamics, J. Timothy Middendorf

Theses and Dissertations

Previous work in the area of estimation of relative positions within a satellite cluster showed favorable results. However, the work was done using point mass orbits in the truth model. This thesis investigates the estimation of relative satellite positions operating in near circular orbit including the J₂ term in Earth's geopotential. The iterated, extended Kalman filter is used as the on-board estimator in order to gain better performance in the face of the non-linearities. The dynamics in the estimator are based on the Clohessy- Wiltshire equations for relative orbital motion. Inputs to the host estimator are range measurements from …

Perturbation Theory For Restricted Three-Body Orbits, David A. Ross

Theses and Dissertations

A perturbation theory for restricted three-body orbits, using a periodic trajectory as a reference solution, is investigated. The nearly- periodic equations of motions are derived by analogy to a linearization about an equilibrium point. In this case, the linearization produces a set of time- periodic equations of motion that, according to Floquet, are completely solved by a periodic trajectory. The four-dimensional phase space of the restricted three-body problem is the first surveyed for regions of periodic motion, via the surface of section phase plot. Upon extraction of a periodic orbit, nearly- periodic orbits are integrated. The integrated state vector is …

Thrust Vector Control Of An Overexpanded Supersonic Nozzle Using Pin Insertion And Rotating Airfoils, Curtis R. Amble

Theses and Dissertations

An experimental study of probe thrust vector control of overexpanded supersonic flow in nozzles using movable probes as the vectoring mechanism is presented. Two type of movable probes were used. The first inserted cylindrical proves through the wall of the nozzle to set depths relative to the nozzle wall; the second used rotating airfoils, inserted within the nozzle flow, rotated to various angles of attack relative to the nozzle centerline. Effectiveness of these probe thrust vector control mechanisms was investigated for a confined jet and conical nozzle. The study objective was to evaluate performance and transient characteristics of these probe …

Effect Of Nonuniform Entrance Flow Profile On Hypersonic Nozzle Pitching Moment, Sandra L. Snelling

Theses and Dissertations

The Scramjet Hypersonic Nozzle (SCHNOZ) parabolized Navier-Stokes computer code was used to model turbulent, chemically reacting flow present in a hypersonic nozzle. Two nozzle configurations were considered, an isolated nozzle (no external flow) and a nozzle with a finite length cowl. A single nonuniform entrance flow profile was generated and an equivalent uniform flow profile calculated for input into the nozzle code. Uniform and nonuniform cases for each nozzle were run using both frozen and finite rate chemistry. An increased grid resolution in the computer code was necessary to eliminate numerically induced anomalies in the results of the nonuniform cases …

Application Of Mixed H2/H∞ Optimization, John J. Kusnierek

Theses and Dissertations

A non-conservative optimization technique is utilized to examine the problem of minimizing the 2 norm of one transfer function subject to an ∞-norm bound on another transfer function. For single exogenous input/ single exogenous output systems this non conservative mixed solution is shown to be up to 5% better in a specific example. For single exogenous input/two exogenous output systems the mixed solution is shown to be up to 27% better than a previous technique for a specific example. Finally, a two exogenous input/two exogenous output practical system is examined to demonstrate the utility of this mixed optimization technique.

Application Of Low Thrust Propulsion Techniques To Satellite Attitude Control Systems, Jeffrey J. Abbott

Theses and Dissertations

Equation of motion for a satellite controlled through continuous, low thrust propulsion systems are analyzed through numerical integration techniques. The equations of motion are derived using the Euler Moment Equations. The properties of the satellite model are based upon the Intelsat VII design of communications satellite. A simple rate and error feedback controller is used in providing active attitude control about two and three axes. Perturbation models are created and applied based upon the satellite model. Parameters varied include thrust levels and controller deadband widths. System response times, pointing accuracy, and total impulse required for attitude control are determined as …

Comparative Analysis Of Guidance Algorithms For The Hyper Velocity Missile And Afti/F-16, Edward G. Rice

Theses and Dissertations

This project has provided me with endless intrigue. In considering the problem of guiding a hyper-velocity missile from a moving platform to a moving target, a common perception said it was just another Kalman Filtration design challenge. I began with lofty intentions of running a full up extended Kalman filter simulation but I became enthralled with the limited work available on the physical limitations of basic guidance algorithms. This became the emphasis of this project. The best filter scheme cannot overcome a guidance algorithms physical limitation. Only with an understanding of these limitations can one effectively integrate a guidance scheme …

Linearized Dynamics Of Space Structures With Articulated Appendages, Gopichand Koganti

Mechanical & Aerospace Engineering Theses & Dissertations

The inherent difficulties of the conventional spacecraft design, which first considered the optimization with respect to structural variables and then with respect to control variables, have led to the concept of Controls-Structures Interactive Design. The success of the CSI design of Space structures without articulated appendages has prompted the extension of the CSI design to systems with articulated appendages. The presentation is of two parts, the first part deals with the derivations of the equations of motion and the second part deals with the eigenvalue/vector approximations.

Three approaches, namely: the multibody approach, the finite element based approach with hinge joints …

Finite Element Frequency Domain Solution Of Nonlinear Panel Flutter With Temperature Effects And Fatigue Life Analysis, David Yongxiang Xue

Mechanical & Aerospace Engineering Theses & Dissertations

A frequency domain solution method for nonlinear panel flutter with thermal effects using a consistent finite element formulation has been developed. The von Karman nonlinear strain-displacement relation is used to account for large deflections, the quasi-steady first-order piston theory is employed for aerodynamic loading and the quasi-steady thermal stress theory is applied for the thermal stresses with a given change of the temperature distribution, ΔΤ (x, y, z). The equation of motion under a combined thermal-aerodynamic loading can be mathematically separated into two equations and then solved in sequence: (1) thermal-aerodynamic postbuckling and (2) limit-cycle oscillation. The Newton-Raphson iteration technique …

Model Identification And Control System Design For The Lambda Unmanned Research Vehicle, Gerald A. Swift

Theses and Dissertations

Research for this thesis centered on the Lambda Unmanned Research Vehicle (URV), an asset of the Flight Dynamics Directorate, Wright Laboratory Patterson AFB. The following tasks were accomplished: (1) a linear, state-space, small perturbation model was developed for both the longitudinal and lateral directional dynamics of the vehicles, and (2) pitch rate roll rate, and yaw rate flight controllers were designed using classical and multivariable feedback methods. The parameters of the linear, state space, small perturbation model were estimated from actual flight test data. Digital Datcom was first used to estimate stability and control derivatives from the vehicle's geometry. Maximum …

Higher-Order Thickness Expansions For Cylindrical Shells, Randy A. Smith

Theses and Dissertations

Eight variations of higher-order transverse shear deformation (HTSD) theory were developed for composite shells. Three attributes were varied to produce the eight variations. These attributes include the order of the thickness expansions used to approximate the shell shape factors and the assumed linear displacement field and the nonlinearity of transverse shear strain. Several cylindrical shell problems were investigated using SHELL, a finite- element code with a 36 degree of freedom cylindrical shell element. MACSYMA, a symbolic manipulation code, was used to formulate the element independent stiffness arrays for each variation of the theory. When all nonlinear strain- displacement terms for …

Investigation Of Advanced Aircraft Performance Measures Of Merit Including New Agility Metrics, Bruce A. Fox

Theses and Dissertations

Advanced aircraft performance measures of merit have been proposed and individually analyzed by various researchers. These metrics have been consolidated into a single computer code as part of this research effort. This code was used to study the relationships between the advanced metrics, aircraft design metrics and an aircraft's trajectory performance. The study found a linear relationship existed between the advanced metrics and the design metrics. This relationship was used to quantify the required levels of the advanced metrics which would give desired changes in trajectory performance. The results showed that advanced metrics could be applied only to very specific …

Finite Element Analysis Of Nonlinear Panel Flutter Of Rectangular Composite Plates Under A Uniform Thermal Load, Lain Ross Dixon

Mechanical & Aerospace Engineering Theses & Dissertations

A finite element formulation is developed to analyze large-amplitude panel flutter of arbitrarily laminated composite plates subjected to a uniform temperature change. The plates considered are anisotropic composite, thin rectangular panels. The aerodynamic pressure load is modeled through the use of the first-order piston theory. The equations of motion for the oscillating plate are determined from the principle of virtual work. Two different solution procedures are given to determine the panel motions. The first procedure, which considers only the aerodynamic load, solves the panel limit-cycle motions by employing the linearized updated-mode with a nonlinear time function (LUM/NTF) approximation. The second …

Application Of Sensitivity Analysis To The Euler Equations, Vamshi Mohan Korivi

Mechanical & Aerospace Engineering Theses & Dissertations

An approximation method is presented for efficiently predicting the changes which occur in a steady-state numerical solution of the Euler equations as a consequence of a small change in the geometric shape of the domain. The method is extended to develop a general procedure for calculating aerodynamic sensitivity derivatives with respect to variations of geometric shape. The techniques are implemented using an upwind cell centered finite volume formulation, and are applied to two test cases, (1) a subsonic nozzle (M_∞ = 0.85), and (2) a supersonic inlet (M_∞ = 2.0). Conventional numerical solutions are first obtained for flow …

Integrated System Identification And Adaptive State Estimation For Control Of Flexible Space Structures, Chung-Wen Chen

Mechanical & Aerospace Engineering Theses & Dissertations

Accurate state information is crucial for control of flexible space structures in which the state feedback strategy is used. The performance of a state estimator relies on accurate knowledge about both the system and its disturbances, which are represented by system model and noise covariances respectively. For flexible space structures, due to their great flexibility, obtaining good models from ground testing is not possible. In addition, the characteristics of the systems in operation may vary due to temperature gradient, reorientation, and deterioration of material, etc. Moreover, the disturbances during operation are usually not known. Therefore, adaptive methods for system identification …

An Experimental And Analytical Investigation Of Wing Flutter On A Trial Rotor V/Stol Aircraft, David L. Soistmann

Mechanical & Aerospace Engineering Theses & Dissertations

A wind tunnel model based on a trail rotor vehicle concept was tested for wing flutter in the subsonic flow regime. The wind tunnel model was flutter tested in the forward flight mode only. From this test it was determined that this conceptual vehicle may be susceptible to wing flutter. However, the flutter encountered was not catastrophic but was of the limited amplitude type. The trailing rotor blades were found to have a positive aerodynamic damping effect on flutter. The flutter mechanism for each flutter point was due to a coupling of the first wing bending and first wing torsion …

The Solution Of A Singular Integral Equation Arising From A Lifting Surface Theory For Rotating Blades, Mark H. Dunn

Mathematics & Statistics Theses & Dissertations

A technique is presented for the solution of a linear, two dimensional, singular, Volterra integral equation of the first kind. The integral equation, originally developed by Farassat and Myers, is derived from the basic equations of linearized acoustics and models the lifting force experienced by an infinitesimally thin surface moving tangent to itself. As a particular application, the motion of modern high speed aircraft propellers (Advanced Technology Propellers) is considered. The unknown propeller blade surface pressure distribution is approximated by a piecewise constant function and the integral equation is solved numerically by the method of collocation. Certain simplifying assumptions applied …

Cognitive Learning Styles And Their Relation To Air Traffic Control Screening And Training, Vincent P. Galotti

Master's Theses - Daytona Beach

The purpose of this study was to show a relationship between the type of cognitive learning style that an individual possesses and their subsequent success at simulated air traffic control practical exercises. Kolb's Learning Style Inventory was utilized to determine dominant learning styles of 30 college students enrolled in a laboratory-based air traffic control course. The instrument was administered during the first day of classes in the Fall of 1990. Students were placed in one of four groups for statistical purposes according to learning style. The scores of simulated micro-computer based air traffic control practical exercises given at semester's end …

Development Of A Personal Computer Simulation Program Of The Ln-94 Inertial Navigation System, Thomas E. Flynn

Theses and Dissertations

This thesis develops a simulation that emulates a Litton LN-94 INS. Real time simulation is achieved for a stationary navigation case and a straight-and-level flight trajectory are provided to exercise the simulation dynamics. The user interface is simple and requires little previous knowledge to operate. The communication link with the MILSTD 1553B bus provide a realistic environment in which to collect and analyze data. The simulation is processed on an 80386 IBM compatible personal computer. A 23-state INS error model is implemented and integration is performed by a fifth-order Kutta-Merson routine. The simulation is interfaced to a plotting routine and …

Experimental Evaluation Of Design Variables For Two-Dimensional Confined Jet Thrust Vector Control Nozzles, Timothy M. Hawkes

Theses and Dissertations

An experimental study of the axial and vectoring performance of two - dimensional (2-D) confined jet thrust vector control (CJTVC) nozzles was performed. The effects of adding secondary injection ports and changing exit height and secondary injection port location were studied on several 2-D CJTVC nozzles. The axial and vectoring performance results for these nozzles were measured over a range of pressure ratios. An analytical method for predicting flow separation was found to be applicable to these nozzles. Guidelines for designing 2-D CJTVC nozzles, that can be vectored using secondary injection, were established.

Vertical And Angular Motion Of A Wing Model In Steady Flow: A Physical And Numerical Experimental Study, Andrew P. Johnston

Opportunities for Undergraduate Research Experience Program (OURE)

The dynamic response of a rigid wing in steady flow mounted on translational and rotational elastic supports is investigated. This study presents both a numerical and a physical experimental arrangement that can be employed to investigate the effect of a wide range of parameters on the response of the wing subjected to steady flow. An interactive computer program, which utilizes the fourth order Runge-Kutta integration scheme to solve the governing differential equations, is discussed. The program output allows for quick visualization of the change in response due to parameter changes. An experimental arrangement that utilizes the new 18" x 18" …

Development Of A Large Commercial Transport Model For A Real-Time Digital Flight Simulator, John Francis Winkler

Opportunities for Undergraduate Research Experience Program (OURE)

In order to test the adaptability of the University of Missouri-Rolla's flight simulator to different types of aircraft, a basic mathematical model of a large commercial transport aircraft is developed. The original aircraft model is based on the Cessna 210, and in order to accommodate the drastic differences between the Cessna 210 and the Boeing 747, many changes are made to the simulation code. The aircraft geometric data, stability and control derivatives, and weights data are altered to match those of the 747. Changes are made within the various subroutines to include thrust reversal, spoilers, and a variable incidence horizontal …

Modeling For Supersonic Missile Wing-Body Interference Lift, Howard S. H. Ho

Opportunities for Undergraduate Research Experience Program (OURE)

During the initial phase of a missile design, a quick and simple way of estimating wing-body interference is essential. A simple panel model based on the cross flow over a cylinder is developed to estimate the effect of the body on the wing lift This model produces quick and reasonably accurate results, while little user expertise is needed. This model determines K_WB (upwash interference factor) and K_Φ (sideslip interference factor), and is applicable to infinitely thin delta and clipped delta fins on missiles in supersonic flight. The effects of the fin semivertex angle, span, taper ratio, free stream …

Some Stability And Control Aspects Of A Variable Pivot Wing Configuration, Paul Vitt

Opportunities for Undergraduate Research Experience Program (OURE)

In supersonic flight, there is a large positive shift in the static margin, which causes extreme positive shifts in longitudinal stability, and is an undesirable characteristic. This paper investigates some of the stability and control aspects of an alternative configuration, that of a variable pivot wing aircraft -- an aircraft with two sets of wings, one set sweeps forward, the other set sweeps rearward. By prescribing a sweep schedule, it is desired to minimize the static margin shift with Mach number. The effects of the two lift elements -- that of mechanical shift of the center of pressure forward with …

Computer Visualization Of Irrotational Flow Over Bluff And Streamlined Bodies, Nora Okong' O

Opportunities for Undergraduate Research Experience Program (OURE)

Computer programs were developed to visualize irrotational flow over bluff bodies (circular cylinders and half-bodies) and streamlined bodies (elliptical cylinders and airfoils). The method of superposition of flows was used, with stream functions or complex velocity potentials for fundamental flows being added to obtain the flows over the bodies. For the flow over the circular cylinders, half-bodies and elliptical cylinders, the stream function was calculated directly. The flow over the airfoil was obtained by Joukowski mapping of the imaginary part of the complex velocity potential for flow over a circular cylinder.

The programs developed will be valuable learning tools for …