Aerodynamic pressures on vortex-shedding struts

Abstract

New measurements will be presented of the aerodynamic pressures induced at trailing edges of rigid struts. These pressures are generated with a sinuous time dependence when the wake of the strut is characterized by a von Karman vortex street. The variation of the surface pressure with upstream distance from the trailing edge is given for a series of edge configurations. These include varying ratios of trailing edge thickness to the thickness of the boundary layer which separates at the edge, as well as variations in the edge geometry. The mean-square pressures are found to depend on x−1, where x is the upstream distance from the edge, within ten edge-thicknesses of the edge. Spatial surveys of the disturbances in the wake provide intensity and length scales which reflect the shed vortex strength and structure and they therefore relate to the magnitudes of the pressures. A dimensional analyses is presented which specifies this relationship. The resulting dimensionless chordwise distribution of fluctuating pressure is shown to be given by an empirical function which is similar for all edges examined.