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Second Symposium on Turbulence and Shear Flow Phenomena
June, 27-29, 2001, KTH, Stockholm, Sweden

DOI: 10.1615/TSFP2

MULTIPOINT MEASUREMENT OF WALL PRESSURE FLUCTUATIONS IN A SEPARATED AND REATTACHING FLOW OVER A BACKWARD-FACING STEP

pages 411-416
DOI: 10.1615/TSFP2.2320
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SINOPSIS

Time-dependent characteristics of wall pressure fluctuations in separated and reattaching flows over a backward-facing step were investigated by means of continuous wavelet transform. Emphasis was placed on the combination of time-localized analyses of wavelet transform and multi-point measurements of pressure fluctuations. Synchronized wavelet maps revealed the evolutionary behavior of pressure fluctuations and gave further insight into the modulated nature of large-scale vortical structures. It was found that there exist two modes of shed vortices: one is the global oscillation and the other is the vortex convection. The two alternating modes are synchronized with the flapping frequency component of pressure fluctuations. Toward the investigation of the direct relationship between the flow field and the relevant spatial mode of the pressure field, a new kind of wavenumber filtering of pressure distribution, termed as a spatial box filtering (SBF), is introduced and examined. The conditional averaged velocity time history reveals that this SBF mode, tuned with the length scale of large-scale vortical structure, suggests its usefulness in capturing the large-scale coherent vortical structure.

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