The Interaction of a Bluff Body with a Vortex

A theoretical, experimental and numerical study is presented of the interaction of a vortex wake created by an upstream blade with a downstream prismatic block. The aim of the study is to investigate the fundamentals of force and noise generation for this type of flow and explain how inter-object spacing affects the far-field noise level. A theoretical model, based on a compact form of Curle’s formulation, is developed and shows that acoustically constructive or destructive interference is determined by the amplitude and phase of the forces on each object as well as the Strouhal number. Experimental and two-dimensional, unsteady numerical results of the vortex wake interaction case are presented for several blade-block separation distances. Using a combination of this experimental and numerical data, the theoretical model is able to explain observed variations in far-field noise level with blade-block separation distance. The numerical model accurately predicts the phase relationship between the unsteady forces on each object. Numerical flow visualisation shows that this phase difference is controlled by the aerodynamic interference effects caused by the downstream block