Flow and Noise Characteristics of Blunt-Trailing-Edge Flat Plate with an Upstream Cylinder

Abstract

This paper experimentally studies the flow interaction and the associated noise between an upstream cylinder and a downstream finite-chord-length flat plate with a blunt trailing edge in an acoustic wind tunnel. The configuration of this cylinder–plate model varies by changing the cylinder diameter and the vertical gap between the cylinder and the flat-plate surface. Aerodynamic noise was measured using far-/near-field microphone arrays. The results show that, as compared to the single flat plate, the trailing-edge noise associated with the vortex shedding from the flat plate is significantly suppressed when the gap is : that is, when the cylinder is vertically close to the flat-plate surface. In addition, the corresponding vortex shedding frequency decreases visibly. The leading-edge interaction noise due to the cylinder wake impingement gradually loses its dominance with the increase of the vertical gap. Compared to the single cylinder, the vortex shedding frequency from the upstream cylinder in the cylinder–plate model is reduced slightly due to the acoustic feedback from the plate leading edge. Flow characteristics were measured using surface microphones and particle image velocimetry (PIV) techniques. The pressure fluctuations along the plate surface present the dominant frequencies at the leading edge and the trailing edge, respectively, and verify the changes in the peak frequency and its noise level. The PIV technique clearly shows the variation of the vortex–body interaction at the leading edge and the vortex shedding at the trailing edge, revealing the underlying flow mechanism responsible for the observed noise changes and frequency shifts.