Wall-pressure coherence beneath a low Reynolds number turbulent boundary layer

Abstract eng:
Measurements of the unsteady wall-pressure field are acquired on the floor of a wind tunnel beneath a fully developed, zero pressure gradient turbulent boundary layer with a Reynolds number based on momentum thickness, Reθ of 2593. The single point wall pressure spectrum and the streamwise coherence lengths are reported. The coherence lengths of streamwise pressure fluctuations are larger than predicted using existing models, and shows that large irrotational outer layer motions retain their coherent power for streamwise separations exceeding 3.6 boundary layer thicknesses, while smaller, high-frequency fluctuations decay within 0.75 boundary layer thicknesses. Further investigations with finer spatial resolution are required to understand the coherent nature of high-frequency pressure events.

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