QC 20110617

No description available.

No description available.

No description available.

No description available.

A review of the past wind tunnel experiments involving the measurement of pressures over the surface of a hemispherical dome is made, and the flow parameters of these experiments are compared. A hemispherical dome is subjected to a flow in the open-throat wind tunnel at VPI&SU, and the resulting pressure measurements are given. An experiment utilizing the 6-ft square stability wind tunnel at VPI&SU to measure the pressures over the surface of a hemispherical dome is organized but not conducted. ABAQUS, a nonlinear finite element program, is used to analyze a hemispherical, lamella dome subjected to a wind load. The dome is first modeled by using truss elements and then beam elements. A comparison of the two models is made. / M.S.

A study is conducted to analyze the performance of different turbulence models when applied to flow through a Mach 7.4 hypersonic inlet. The analysis, which is two-dimensional, is done by comparing computational results from a Parabolized Navier Stokes code, with experimental data. The McDonald Camarata (MC) and Baldwin Lomax (BL) models were the two zero-equation models used in the study. The Turbulent Kinetic Energy (TKE) model was chosen as a representative higher order model. The MC model, when run with transition of flow, provides a solution which compares excellently with the data. Transition has a first order effect on the overall solution provided by the code. The BL model predicts separation of flow in the inlet, which contradicts experimental findings. The TKE model does not perform any better than the MC and BL models, despite the fact that it is a higher order turbulence model. The BL and TKE models predict transition in the inlet at a location which is much earlier than observed in the experiment. This may be attributed to the empirical constants used to determine the point of transition. / M.S.

Existing subsonic wind tunnel methods for obtaining dynamic stability derivatives for aircrafts at high angle of attack are described. From the general equations of motion of an aircraft in space, the perturbation equations of motion are derived for applying to a wind tunnel aircraft model. Data Reduction and test procedures for important dynamic tests are evolved systematically from the restrained perturbed equations of motion. Emphasis is given to the typical single degree of freedom apparatuses and associated data reduction for routine measurement of dynamic stability derivatives due to pitching, rolling and yawing of the model. The translational and snaking motion apparatuses from which the derivatives, α, β, and p, q, r are measured separately, are also presented. Finally, for the purpose of increasing the capabilities of the Virginia Tech dynamic test systems, a single degree of freedom forced oscillatory rig, which gives the exact sinusoidal displacement of the model and also adjustable to the existing curved and rolling flow facilities, is described with its data acquisition/reduction. / Master of Science

A wind tunnel was designed and built to produce a pulsating flow. The pulsation was achieved by a series of shutters (rotating with constant angular velocity) placed upstream of the settling chamber inlet. The system was optimized to obtain nearly sinusoidal velocity waveforms with the highest obtainable amplitudes over the frequency range of 3.4 to 31.3 Hz. The velocity and pressure waveforms are given for different shutters settings and conditions. It was found that the velocity waveform shape and amplitude, obtained in the test section, are a strong function of pressure build-up in the diffuser upstream of the shutters box. An explanation is given, for various shutters settings and conditions, of how pressure release is achieved and how the pressure waveforms are generated. / M.S.

Two aspirating hot-film probes are developed to make measurements in supersonic air/helium shear layers. The first probe is designed to measure local mean gas composition and is referred to as the mean concentration probe. This probe consists of a constant temperature hot-film sensor operating in a channel with a choked exit. The flow over the hot-fifm is influenced only by total temperature, total pressure, and gas composition. The mean probe is easily calibrated and shows acceptable sensitivity to flow angularity. The second probe is based on an improved design of the mean concentration probe. In addition to measuring mean composition, this second probe also measures turbulence intensities of Reynolds number and thermal conductivity using a multiple overheat method. This probe is referred to as the turbulent probe. Both probes are used in the study of supersonic air/helium mixing layers in the VPI&SU 23 cmx23 cm Supersonic Wind Tunnel. Profiles of mean and turbulent quantities are presented. / Master of Science