Accession Number : ADA313262

Title :   A Collaborative Study of Turbulence-Generated Noise and Development of Fast Image Correlation Velocimetry Techniques.

Descriptive Note : Final technical rept. 31 Jul 91-31 Mar 95,

Corporate Author : CALIFORNIA UNIV SAN DIEGO LA JOLLA

Personal Author(s) : Gharib, Morteza

PDF Url : ADA313262

Report Date : 30 JUN 1995

Pagination or Media Count : 110

Abstract : The overall goal of this project has been to develop a new technique to predict hydrodynamic radiation from complex flows. The approach relates the fluctuations at the edges of a flow field to its far-field acoustic signature. Only recently have time-resolved, global velocity measurement techniques been developed that allow investigation of Liepmann's method. In this project, we attempted to develop an understanding of various parameters for the model and develop new tools for their measurements. The approach we have taken has been to formulate the near-field displacement effects of shear flows such as jets and stratified shear layers, in the sense of boundary layer theory, and relate to the far-field sound pressure. To do this, we used laser-induced fluorescent imaging, digital article image velocimetry, and scalar imaging velocimetry, to study temporal and spatial behavior of the various stratified and non-stratified flows. Our accomplished tasks constitute major advances toward our stated goal: (1) Completed a major study of the dynamics of the stratified shear layers, especially as it relates to the most important scales for the Liepmann model. (2) Made extensive flow measurements of 3D submerged, temporal mixing layers. (3) Demonstrated the role of 3D vortical structures on the entrainment fluctuations. (4) Advanced the state-of-the art in image processing, specifically, the correlation of a pair of images, recorded in quick succession in time, to extract velocity-field information. (5) Designed and fabricated a dual-image CCD device to record a pair of images, as close as 1-2 microseconds apart, for the purpose of estimating the image in-plane velocity field in moderate to high-speed flows.

Descriptors :   *FLOW FIELDS, *ACOUSTIC SIGNATURES, *HYDRODYNAMICS, MATHEMATICAL MODELS, IMAGE PROCESSING, SPATIAL DISTRIBUTION, LASER INDUCED FLUORESCENCE, TURBULENCE, OPTICAL IMAGES, VORTICES, FLOW VISUALIZATION, VORTEX SHEDDING, FAR FIELD, FLOW NOISE, MIXED LAYER(MARINE), STRATIFICATION, SOUND PRESSURE, ACOUSTIC FIELDS, SHEAR FLOW, BOUNDARY LAYER FLOW, LASER VELOCIMETERS, THREE DIMENSIONAL FLOW, CHARGE COUPLED DEVICES, JET MIXING FLOW.

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE