Accession Number : ADA314537

Title :   Identification of Coherent Motions using Wall Pressure Signatures.

Descriptive Note : Rept. for Nov 95-Nov 96,

Corporate Author : CATHOLIC UNIV OF AMERICA WASHINGTON DC DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Jayasundera, Srinath ; Casarella, Mario ; Russell, Steven

PDF Url : ADA314537

Report Date : AUG 1996

Pagination or Media Count : 36

Abstract : Large amplitude wall-pressure events observed beneath a turbulent boundary layer appear to be signatures of near-wall organized structures. Experimental investigations by the authors and their colleagues have provided strong support for this conjecture. This report contains results from new studies which attempt to identify the distinct structural features and spatial extent of the organized motions from observations of their wall pressure footprints. A database, which contains simultaneous measurements of wall-pressure, and stream-wise and wall-normal velocities at numerous locations across the boundary layer, was used in this investigation. These data are analyzed using signal processing techniques based on a trajectory mapping for the detection of coherent motions. The results show that the organized structures contain both ejection motions (accelerated events) that induce positive wall pressure events; and sweep motions (decelerated events) that induce negative wall pressure events. It is proposed that these structures collectively represent the organized motions. The present research activity is directed at the acquisition of a new database using an array of streamwise and spanwise transducers. By applying bandpass filtering techniques to the data, it is expected that the total pressure signature will become more evident.

Descriptors :   *TURBULENT FLOW, *PRESSURE DISTRIBUTION, *PRESSURE SIGNATURES, HEAT TRANSFER, PRESSURE GRADIENTS, DATA BASES, ALGORITHMS, SIGNAL PROCESSING, PRESSURE TRANSDUCERS, TURBULENCE, TURBULENT BOUNDARY LAYER, VORTICES, COMPUTATIONAL FLUID DYNAMICS, PRESSURE MEASUREMENT, FLOW FIELDS, WALLS, BANDPASS FILTERS, BOUNDARY LAYER FLOW, PIPE FLOW.

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE