Aerodynamics and Fluid Mechanics Commons^™

High-Resolution Tvd Schemes For The Analysis Of 1. Inviscid Supersonic And Transonic Flows. 2. Viscous Flows With Shock-Induced Separation And Heat Transfer, Mark A. Driver

Theses and Dissertations

Application of TVD schemes to both inviscid and viscous flows is considered. The mathematical and physical bases of TVD schemes are discussed. First and second-order accurate TVD schemes and a second-order accurate Lax- Wendroff scheme are used to compute solutions to the Riemann problem in order to investigate the capability of each to resolve shocks, rarefactions, and contact surfaces. Second-order finite-volume and finite-difference TVD schemes are used to obtain solutions to inviscid supersonic and transonic cascade flow problems. TVD schemes are shown to be superior to the Lax-Wendroff family of schemes for both transient and steady-state computations. TVD methodology is …

Thermal Nonequilibrium Effects On Turbine Cascade Aerodynamics, Jill L. R. Shaw

Theses and Dissertations

The AFIT Total Variation Diminishing Euler Code (ATEC) was modified to include a thermal nonequilibrium model to investigate high temperature effects associated with vibrational relaxation in a transonic turbine cascade. Incorporation of this model into ATEC and creating ANTEC (AFIT Nonequilibrium TVD Euler Code) was accomplished in three steps. Steady-state solutions obtained with ANTEC were compared with those obtained with ATEC for various inlet and exit conditions. The Courant-Friedrichs-Levy criterion was held constant to ATEC; however, it required variation for ANTEC. Blade temperature profiles, temperature difference contours in the vicinity of the trailing edge and the value of the ratio …

A Comparative Study Of Numerical Versus Analytical Waverider Solutions, Gregory O. Stecklein

Theses and Dissertations

The WL/FIMM explicit, Roe flux-splitting Euler algorithm is applied to the inviscid hypersonic flow over a parabolic-top waverider configuration optimized for Mach 10 at zero degrees angle of attack. An on-design grid refinement study is conducted to determine the asymptotic nature of the optimized flight parameter L/D. A parametric study of off-design conditions is conducted to determine flow perturbation effects on HSDT waverider theory. A validation of the Euler code is conducted through a comparison of the numerical data to analytical results derived by Rasmussen. The grid refinement study shows little effect on the inviscid calculation of the optimized parameter …

An Experimental Study Of A Sting-Mounted Circulation Control Wing, Steven J. Lacher

Theses and Dissertations

This wind tunnel study investigated the lift, drag, and pitching moment of a 20% thick, 8.5% camber, partial elliptical cross-section, single blowing slot, 2.325 aspect ratio, rectangular circulation control wing. The AFIT 5-foot wind tunnel was used. Lift and drag were referenced to the wind axis. The Reynolds number was 500,000 for all tests. Angle of attack was varied from -6 to 16 degrees and the effects of pulsed blowing were investigated. Effects of tripping the Coanda jet with a small flow barrier attached spanwise along the Coanda surface were also studied. Results indicate that there is a limit on …

Investigation Of The Influence Of Rotary Aerodynamics On The Study Of High Angle Of Attack Dynamics Of The F-15b Using Bifurcation Analysis, Ralph D. Fero

Theses and Dissertations

The purpose of this research was to use bifurcation analysis to investigate the effectiveness of rotary balance data in the prediction of aircraft spin behavior as both a stand alone representation of a model's aerodynamic data and in a conventional hybrid model. using the foundation of a previously developed model of the F-15B, the rotary balance aerodynamic force and moment data were implemented as a function of angle of attack, angle of sideslip, non-dimensional rotation steady state rate and the control surface deflections. Bifurcation diagrams were developed as a function of alpha vs. deflection angles of, the rudder, stabilator, and …

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 …

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 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 …

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 …

Effect Of Passive Flow-Control Devices On The Drug Of A Tractor-Trailer Model, Jagjit K. Ahuja

Mechanical & Aerospace Engineering Theses & Dissertations

The aerodynamic drag of tractor trailers is responsible for approximately half of the fuel consumption at highway speeds (55m.p.h.). Thus, it is important that vehicle drag be reduced in order to reduce operating costs and to conserve fuel. The purpose of the subject research conducted in the Old Dominion University Low-Speed Wind Tunnel was to determine the effect of various add-on flow-control devices, such as a cab-mounted flow deflector and gap seals between the tractor and the trailer. In addition, the effect of trailer rear-edge shaping has been studied. This was accomplished by contouring the trailer's rear end. It has …