Investigation of Spanwise Behavior of a Turbulent Boundary Layer affected by a Micro-Cavity Array

Abstract

A micro-cavity array is a micro-perforated plate with strategically placed cavities designed to target and attenuate sweep events present within a turbulent boundary layer. This paper aims to investigate the spanwise behavior of a turbulent boundary layer exposed to micro-perforations by examining the effects a large array (spanning the full width of a flat plate channel) may have on the boundary layer across a locus of spanwise and downstream locations. Air velocity data was obtained experimentally using single-component hot-wire anemometry on a single micro-cavity array geometry. Two distinct free-stream velocities flows were investigated: U∞=12.1 and 19.1 m/s for cases where the array was installed, and one for a canonical flat plate environment. Sixteen locations were investigated downstream of the array, four spanwise and four streamwise, with data between configurations taken at identical locations for the purpose of comparison. The large array has been shown to modify streamwise turbulence intensity and sweep event intensities across almost all locations and Reθ investigated. Across the spanwise direction, there is no evidence to suggest that the micro-cavity array imposes any significant changes in flow characteristics to the boundary layer. Through analysis of the pre-multiplied energy spectra, it was observed that changes in streamwise turbulent kinetic energy stemmed from the near-wall region of the boundary and travel with some lag to the outer region.