signature=27fe40dfd620feec0260ffd4e7d59216,APS

63rd Annual Meeting of the APS Division of Fluid Dynamics

Volume 55, Number 16

Sunday–Tuesday, November 21–23, 2010;

Long Beach, California

Session LB: Turbulent Boundary Layers VI

3:35 PM–5:45 PM,

Monday, November 22, 2010

Long Beach Convention Center

Room: 101B

Chair: Ronald J. Adrian, Arizona State University

Abstract ID: BAPS.2010.DFD.LB.7

Abstract: LB.00007 : Very-Large-Scale Coherent Structures in the Wall Pressure Field Beneath a Supersonic Turbulent Boundary Layer

4:53 PM–5:06 PM

Authors:

Steven Beresh

(Sandia National Laboratories)

John Henfling

(Sandia National Laboratories)

Russell Spillers

(Sandia National Laboratories)

Brian Pruett

(Sandia National Laboratories)

Previous wind tunnel experiments up to Mach 3 have provided fluctuating

wall-pressure spectra beneath a supersonic turbulent boundary layer, which

essentially are flat at low frequency and do not exhibit the theorized

$\omega ^{2}$ dependence. The flat portion of the spectrum extends over

two orders of magnitude and represents structures reaching at least 100

$\delta $ in scale, raising questions about their physical origin. The

spatial coherence required over these long lengths may arise from

very-large-scale structures that have been detected in turbulent boundary

layers due to groupings of hairpin vortices. To address this hypothesis,

data have been acquired from a dense spanwise array of fluctuating wall

pressure sensors, then invoking Taylor's Hypothesis and low-pass filtering

the data allows the temporal signals to be converted into a spatial map of

the wall pressure field. This reveals streaks of instantaneously correlated

pressure fluctuations elongated in the streamwise direction and exhibiting

spanwise alternation of positive and negative events that meander somewhat

in tandem. As the low-pass filter cutoff is lowered, the fluctuating

pressure magnitude of the coherent structures diminishes while their length

increases.

To cite this abstract, use the following reference: meetings.aps/link/BAPS.2010.DFD.LB.7

signature=27fe40dfd620feec0260ffd4e7d59216,APS -63rd Annual Meeting of the APS D