Wavenumber Spectra of High Magnitude Wall Pressure Events in a Numerically Simulated Turbulent Boundary Layer

Abstract

A method for conditionally sampling the spatial field of the wall pressure beneath a turbulent boundary layer in order to search for high magnitude events and calculate the corresponding wavenumber spectrum is presented. The high magnitude events are found using a simple peak detection algorithm at a fixed instant in time and the wavenumber spectra are calculated using discrete Fourier transforms. The frequency of occurrence for high magnitude positive events is found to be approximately the same as for high magnitude negative events. The contribution of the high magnitude events to the rms wall pressure for various trigger levels is calculated and compared with results from similar experimental studies performed in the time domain. The high magnitude events are shown to occur infrequently and to contribute significantly to the rms wall pressure. Wavenumber spectra from the high magnitude positive and negative events are calculated and compared with the unconditionally sampled spectra. The high magnitude events contain energy focused around a particular stream-wise wavenumber and have high broadband spectral levels.