Passive Control of Pressure Fluctuations Generated by Separated Flow

Measurements of wall-pressure fluctuations have been made in the flow behind a backward-facing step, with a permeable reattachment surface Different configurations are tried, the most successful producing a reduction in peak rms pressure fluctuation of about 13% and a reduction in drag of about 9%. Spectra show that most of the attenuation occurs at low frequendes, and in particular, the flapping frequency in (n ≃ 0.1) is effectively removed. The main reason for this appears to be that the permeable surface inhibits the upstream convection of disturbances produced at reattachment Structural modifications to the pressure-fluctuation field appear to be confined to the region upstream of mean reattachment

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