No description available.

A high-frequency combination probe was used to measure dynamic flow quality in the test section of the NASA Langley 0.3-m Transonic Cryogenic Tunnel. The probe measures fluctuating stagnation (total) temperature and pressure, static pressure, and flow angles in two orthogonal planes. Simultaneous unsteady temperature and pressure measurements were also made in the settling chamber of the tunnel. The data show that the stagnation temperature fluctuations remain constant, and the stagnation pressure fluctuations increase by a factor of two, as the flow accelerates from the settling chamber to the test section. In the test section, the maximum rms value of the normalized fluctuating velocity is 0.7 percent. Correlation coefficients l failed to show vortlcity, entropy, or sound as the dominant mode of turbulence in the tunnel. At certain tunnel operating conditions, periodic disturbances are seen in the data taken in the test section. A possible cause for the disturbances is found to be acoustic coupling of the test section and plenum chamber via the perforated side walls in the tunnel. The experimental data agree well with the acoustic coupling theory. / Master of Science

An experimental investigation of transition in boundary layer flows under the influence of various freestream conditions is described. Velocity profiles are obtained automatically by means of a stepper-motor driven traverse mechanism which carries a hot wire probe connected to a constant temperature anemometer and associated instrumentation. This was achieved by use of a data acquisition and control facility centred around a microcomputer with a Eurocard rack mounted extension. The automatic boundary layer traverse is software controlled and the data obtained is stored in a disc file for subsequent analysis and graphical display. As an integral part of this facility a successful method of obtaining reliable intermittency values from a hot wire signal was developed. The influence of freestream turbulence and pressure gradient upon transition within a boundary layer developing on a flat plate is elucidated by a series of controlled experiments. From the data accumulated, the concept of statistical similarity in transition regions is extended to include moderate non-zero pressure gradients, with the streamwise mean intermittency distribution described by the normal distribution function. An original correlation which accounts for the influence of freestream turbulence in zero pressure gradient flows, and the combined influence of freestream turbulence and pressure gradient in adverse pressure gradient flows, on the transition length Reynolds number R, is presented. (The limited amount of favourable pressure gradient data precluded the extension of the correlation to include favourable pressure gradient flows). A further original contribution was the derivation of an intermittency weighted function which describes the development of the boundary layer energy thickness through the transition region. A general boundary layer integral prediction scheme based on existing established integral techniques for the laminar and turbulent boundary layers with an intermittency modelled transition region, has been developed and applied successfully to a range of test data.

No description available.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains ix, 94 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 35-36).

The aim of this study was to develop and implement a low cost, high speed, flow visualisation tool for 3-D velocity measurement throughout time dependent particle seeded fluid flow volumes. To achieve this, a new high performance wind / water tunnel was designed and constructed using CFD as a design aid. The tunnel provided the necessary platform for obtaining consistent high quality images of fluid flow. Images were grabbed using low cost CCD cameras and downloaded via a PC mounted image capture board, to system RAM. The conventional high cost laser sheet illumination method was replaced with a low cost, portable floodlight system, which enabled both 2-D and 3-D flow volumes to be illuminated. For the 3-D image capture, stereo photogrammetric techniques were employed. Advanced calibration algorithms were developed which automatically detected camera positioning. This reduced the inherent human error associated with setting-up a complex imaging system. 2-D pattern matching and particle tracking algorithms were developed, optimised and tested using real and synthetically generated flow data, to establish practical limits for particle seeding density, particle image size, flow velocity and flow complexity. These results demonstrated that particle tracking was more suited to real-time 3-D applications. The developed algorithms formed the base of a Windows 95/Windows NT package for general purpose analysis of 2-D and 3-D single exposure image streams of particle seeded fluid flow.

Mode of access: Internet via World Wide Web. Available at http://hdl.handle.net/1947/4681. / "November 2005"

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 61-62). Also available via the Internet.

Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

A solution to the current problem of wind tunnel wall interference could be achieved by ventilating the test section and thereby controlling the flow pattern around the model. The motivation for the slotted wall test section arises from the fact that a fully open jet and a fully closed jet introduce corrections of opposite sign to the wind tunnel data. This current work is limited to axisymmetric wind tunnels and solid blockage corrections. Such a tolerant axisymmetric wind tunnel (TAWT), which does not need any correction to the measured flow quantities and which is also independent of the test model shape and size would find wide application in the field of industrial aerodynamics. A numerical model based on a surface singularity potential flow method showed that at 70% OAR (open area ratio) for models of size up to 25% blockage and for three different shapes the tunnel design would yield results (coefficient of pressure) with less than 2% error while such models might need up to 75% data correction if tested in a solid wall wind tunnel. Experiments indicated good agreement with the numerical investigation and at 60% OAR the TAWT gave results close to free air results for all the models tested (up to 25% blockage). / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate