Computation of Surface Pressure Fluctuations

The excitation of structural vibrations by turbulent boundary layer surface pressure fluctuations is an important problem in underwater acoustics. A capability for accurately characterizing these fluctuations, especially the low wavenumber components of the spectrum, is needed to determine the effect of the pressure fluctuations on the excitation of structural vibrations. This capability may also lead to strategies for reducing the effect of the turbulent boundary layer on vibrations. The objective of the Phase I program is to compute the two-dimensional surface pressure fluctuations for one or more prototype flow geometries which possess a dominant perturbation frequency. The dominant perturbation would generate other spectral components in the boundary layer that will be studied in detail. The geometries to be studied could produce low wavenumber spectra with greater magnitudes than typically found for flat plate boundary layers. An advanced computational fluid dynamics approach based on a very large eddy simulation (VLES) of the Navier-Stokes equations will be used as the basis for a study of boundary layer surface pressure fluctuations. The advantage of the VLES technique is not only the reduced computational time for this case, but its capability for treating large, practical geometries with three dimensional fluctuations in Phase II.