Book Description

This document consists of the text and viewgraphs of a paper presented at the ONR Workshop on Nonequilibrium Turbulence held at Arizona State University in Tempe, Arizona, from 10-1 2 March 1993. This workshop was the first step of an ONR Accelerated Research Initiative (ARI) to establish the state-of-the-art for theory, computation, and experimentation relevant to turbulence in a nonequilibrium state, or, more generally, to turbulence in complex flows. The overall goal of the initiative is to understand the behavior of turbulence in such complex conditions in order to advance our prediction and control capabilities. When a cylinder in axial flow is sufficiently long and thin, the growth of the boundary layer results in its thickness exceeding the radius of the cylinder such that the three-dimensional effects due to transverse curvature cannot be neglected. With this condition, the wall of the cylinder provides less constraint on the outer flow and motion of eddies than is experienced in an equilibrium flat plate boundary layer, introducing an avenue for enhanced inner-layer/outer-layer interaction and modified turbulence activity. In this paper, we present results of measurements of the fluctuating wall pressure and turbulent streamwise velocity in the turbulent boundary layer on a cylinder in axial flow to identify the coherent structures that contribute to the fluctuating pressure at the wall. Determining the influence of transverse curvature on the relationship between the wall pressure and velocity field allows examination of its effect on the structure of equilibrium boundary layer turbulence.