Spatial correlation of measured unsteady surface pressure behind a backward-facing step

Abstract

The spatial correlations of the unsteady surface pressure for a backward-facing step were studied experimentally. The measurements were acquired using an array of surface pressure sensors within an anechoic wind tunnel which was designed to minimize acoustic contamination. The maximum Reynolds number based on the step height was 59,200. The spatial characteristics of the surface pressure were studied in two parts. First, a linear array of microphones oriented in the streamwise direction was used to obtain the evolution of the pressure spectra, length scale, and phase speed. Second, an array oriented in the spanwise direction was used to provide the coherence and integral length scales in that direction. The correlation length functions were found to vary with downstream location in the separated region behind the step. After reattachment, the integral scales of the surface pressure continued to increase in magnitude as far as 18 step heights downstream of the step.