An Experimental Investigation of Organized Turbulent Motions and Wall-Pressure Fluctuations in Complex Flows.
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1995
- Accession Number
- ADA307475
Entities
People
- Mark Kammeyer
Organizations
- Naval Surface Warfare Center