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Articles 181 - 189 of 189
Full-Text Articles in Aerodynamics and Fluid Mechanics
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
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 …
Vortex Bursting Over A Unit Area Aspect Ratio Delta Wing Using Vortex Paneling Methods, Donald A. Lorey
Vortex Bursting Over A Unit Area Aspect Ratio Delta Wing Using Vortex Paneling Methods, Donald A. Lorey
Theses and Dissertations
A unit aspect ratio delta wing is analyzes to determine if an unsteady vortex panel method can calculate the vortex bursting of the vortex developed along the leading edge. A two-dimensional vortex panel method is used to investigate wake splitting schemes of the vortex cores that comprise the vortex sheet, or wake. The worthier of the splitting methods is later implemented into the three-dimensional wake. The weighting values of the Kutta equations are investigated for the leading edges, and are determined to be problem specific. An alternative approach to management of the wake data is presented and implemented. The delta …
Computational Investigation Of Circulation Control Turbulence Modeling, T. Bryan Scruggs
Computational Investigation Of Circulation Control Turbulence Modeling, T. Bryan Scruggs
Theses and Dissertations
A computational study of the turbulence model parameters and the effect on the flow field of a circulation control airfoil was conducted. A Beam- Warming algorithm with a modified Baldwin-Lomax turbulence model was used to solve the Navier-Stokes equations. A comparison between the effects of the Bradshaw constant on the flow field about the cylinder and the flow field about an airfoil were to be made. The lack of a steady 'converged' solution for the cylinder precluded the analysis of the flow field about a cylinder. For the airfoil, the separation point moves rearward and an enhanced vortex pattern is …
Analysis Of Hypersonic Blunt-Body Flows Using A Total Variation Diminishing Scheme And The Maccormack Scheme, Montgomery C. Hughson
Analysis Of Hypersonic Blunt-Body Flows Using A Total Variation Diminishing Scheme And The Maccormack Scheme, Montgomery C. Hughson
Theses and Dissertations
An explicit second-order accurate, total variation diminishing (TVD) scheme and the MacCormack scheme are applied to the Euler equations in axisymmetric form to study hypersonic blunt body flows. The modified flux approach of Harten, with modification by Yee, for two-dimensional flows is extended to treat axisymmetric flows. Calculated flow properties for the steady state, blunt body problem such as shock standoff distance, bow shock shape, surface pressure distribution and entropy jump conditions are compared to theory, results from the MacCormack scheme, and experimental data for Mach numbers of 3.0, 4.03, 5.06, 6.03 and 8.1. Additionally, the TVD and MacCormack schemes …
Turbulence Scales In The Passage Of A Linear Turbine Cascade, James L. Acree
Turbulence Scales In The Passage Of A Linear Turbine Cascade, James L. Acree
Theses and Dissertations
Convective heat transfer in a turbine cascade is examined for turbulence effects. Turbulence in the free stream is varied by injection of air through a jet-grid device upstream of the cascade. Pressure and flow patterns on the blade surface, and flow velocity in two components, are examined to determine the effect of the jet-grid. Velocity and velocity fluctuation in two components are measured. Local turbulence scales through the cascade passage are determined, and local turbulent energy dissipation rate is determined. Results indicate injection of air through the jet-grid changes the angle of incidence, and therefore changes the surface pressures and …
An Experimental Study Of A Sting-Mounted Single-Slot Circulation Control Wing, Michael E. Pelletier
An Experimental Study Of A Sting-Mounted Single-Slot Circulation Control Wing, Michael E. Pelletier
Theses and Dissertations
This wind tunnel study investigated the feasibility of using a sting and force balance to measure the aerodynamic forces and moments on a circulation control wing. A 20% this, 8.5% camber, single blowing slot, rectangular wing was designed, built, and tested in the AFIT 5-ft wind tunnel. Lift and drag coefficients were referenced to the stability axis. The Reynolds number for all tests was 950,000; angle of attack was varied from -6 to +6 degrees. Trends in the data were similar to two dimensional data, with the exception of high drag coefficients with increased blowing. Results show it is feasible …
Modelling And Analysis Of Kernel Function And Development Of Equivalent Theodorsen Function For Three-Dimensional Aeroelastic Analysis, John K. Ryder
Modelling And Analysis Of Kernel Function And Development Of Equivalent Theodorsen Function For Three-Dimensional Aeroelastic Analysis, John K. Ryder
Theses and Dissertations
A fractional calculus model is developed for the kernal function under incompressible subsonic flow conditions for rectangular planform airfoils with small aspect ratio. A model valid for restricted regions of the kernel function for compressible subsonic flow conditions is also developed. Additionally, a method for numerically solving the pressure-downwash integral equation for rectangular planform wings of aspect ratio two through ten in incompressible flow is developed. An equivalent Theodorsen function for three- dimensional unsteady flow is developed, enabling the use of simpler two- dimensional aeroelastic equations of motion to fully capture the more complicated three-dimensional effects.
A Study Of A Wind Tunnel Measurement System For Unsteady Pressures Using Pneumatic Transmission Lines, Mohammed Javed Khan
A Study Of A Wind Tunnel Measurement System For Unsteady Pressures Using Pneumatic Transmission Lines, Mohammed Javed Khan
Theses and Dissertations
The application of pneumatic transmission lines theory to a tube-scanning valve system for unsteady pressure measurements in the AFIT 5-foot wind tunnel is investigated. Transfer gains of various tube-scanning valve configurations were experimentally measured and the validity of a theoretical model verified for a frequency range of 20 Hz to 140 Hz. The selected system having a 0.0625-in. ID flexible tube of 84 in. length connected to a scanning valve was installed in the wind tunnel. Unsteady pressures introduced over an 18 percent airfoil at zero angle of attack were measured with this system. Data were collected for 0, 40, …