Wavenumber-Frequency Characteristics of Partial Wall Pressures from Large Eddy Simulations of a Turbulent Channel Flow

摘要

This report documents, for the first time, the wavenumber and frequency characteristics of the mean-shear (MS) and turbulence-turbulence (TT) partial wall pressures. Results show that both the TT and MS pressures are important for the convective pressures, but that the TT pressure dominates in the subconvective wavenumber range. At low frequencies both the buffer layer and logarithmic region contribute significantly to the MS convective pressure; at higher frequencies the buffer layer is dominant. The partial pressures were obtained from two large eddy simulations (LES) of a fully-developed turbulent channel flow; they were computed from the TT and MS source terms from four regions of the channel (viscous shear layer, buffer region, logarithmic region and upper channel). The Reynolds number based on momentum thickness and shear velocity was 24; based on channel half-width and shear velocity, 171. The non- linear terms in the simulation, as well as those pressure source terms were dealiased using the 213 rule. The first simulation, LES8, used the rotational form of the nonlinear terms, whereas the second simulation, LES9, used the skew- symmetric form. Significant differences between the two simulations appear only in the subconvective wavenumber range for the TT spectra that has been integrated over the entire channel, pointing to the fact that the skew-symmetric form, while more expensive, computationally, is more accurate.