Accession Number : ADA307475

Title :   An Experimental Investigation of Organized Turbulent Motions and Wall-Pressure Fluctuations in Complex Flows.

Descriptive Note : Doctoral thesis,

Corporate Author : NAVAL SURFACE WARFARE CENTER DAHLGREN DIV VA

Personal Author(s) : Kammeyer, Mark

PDF Url : ADA307475

Report Date : DEC 1995

Pagination or Media Count : 147

Abstract : The relationship between high-amplitude wall-pressure peaks and near-wall flow structures has been studied for both equilibrium and disturbed turbulent boundary layers. The disturbed flow was that formed downstream of reattachment of the flow over an aft-facing step. In this case, the disturbances were primarily confined to the outer regions of the boundary layer. Simultaneous measurements of the fluctuating wall-pressure and the streamwise and wall-normal velocity were obtained. These measurements were acquired at numerous locations across the boundary layers. A filtering technique based on the wavelet transform was developed to isolate the near-wall motions from the outer-layer disturbances. Correlation and conditional sampling were performed based on the detection of cluster patterns of wall-pressure and turbulence-producing flow events. The results confirm that patterns of large-amplitude wall-pressure events are footprints of the active (turbulence-producing) motions. The results of flowfield mappings show two vortices, one ahead and above the other, that induce the ejection/sweep pattern and concomitant wall-pressure peak aligned to the log-law region. The same generic features were observed for both the equilibrium and disturbed flows, leading to the conclusion that the near-wall motions are weakly coupled to the outer-layer dynamics. The picture is consistent with models proposed by several investigators.

Descriptors :   *TURBULENT FLOW, *TURBULENT BOUNDARY LAYER, VELOCITY, PRESSURE GRADIENTS, DATA BASES, MATHEMATICAL MODELS, ALGORITHMS, STRESS ANALYSIS, RESOLUTION, TURBULENCE, POWER SPECTRA, VORTICES, COMPUTATIONAL FLUID DYNAMICS, PRESSURE MEASUREMENT, CORRELATION, FLOW FIELDS, MATHEMATICAL FILTERS, DATA REDUCTION, SAMPLING, DATA ACQUISITION, CALIBRATION, NONEQUILIBRIUM FLOW, NAVIER STOKES EQUATIONS, VISCOSITY, FLOW SEPARATION, MICROPHONES, SOUND PRESSURE, PRESSURE DISTRIBUTION, REYNOLDS NUMBER, HOT WIRE ANEMOMETERS, INTEGRAL TRANSFORMS, SHEAR FLOW, BOUNDARY LAYER FLOW.

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE