Journal of Fluids and Structures 25 (2009) 867–888 The interaction of a bluff body with a vortex wake D.J.J. Leclercq, C.J. Doolan à School of Mechanical Engineering, The University of Adelaide, Adelaide, SA 5005, Australia Received 11 December 2007; accepted 5 March 2009 Available online 25 April 2009 Abstract 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. 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 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. r 2009 Elsevier Ltd. All rights reserved. Keywords: Vortex–wake interaction; Curle’s formulation; Noise 1. Introduction The buffeting of bluff bodies is of fundamental concern to those involved in the aerodynamics of buildings, bridges, automobiles and aircraft. The fluctuating loads are the cause of fatigue loading, undesirable structural movement and annoying radiated noise that needs to be understood and controlled for better industrial design and improved public health through the provision of quieter living areas. This paper is concerned with the particular case of noise caused by the interaction of a vortex dominated wake (or vortex wake) generated by an upstream body with another, prismatic object. The arrangement of tandem, in-line cylinders is the most investigated form of wake interaction to be found in the literature. Zdravkovich (1987) provides an excellent review of the early work in this area. Examples of more recent studies include the work performed by Papaioannou et al. (2006), who simulated the three-dimensional laminar and early turbulent flow about tandem in-line cylinders. Meneghini et al. (2001) also performed a two-dimensional study for laminar flow about tandem cylinders, while Fitzpatrick (2003) studied the flow and noise generated by turbulent flow over tandem cylinders. As originally classified by Zdravkovich (1987), tandem cylinder flows are considered as a problem in wake interference. The separation between the cylinders sets the type of wake interaction. Essentially, when the cylinders are close to one another, vortex shedding from the upstream cylinder has been found to be suppressed. ARTICLE IN PRESS www.elsevier.com/locate/jfs 0889-9746/$ - see front matter r 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfluidstructs.2009.02.005 à Corresponding author. Tel.: +61 8 8303 8261; fax: +61 8 8303 4367. E-mail address: con.doolan@mecheng.adelaide.edu.au (C.J. Doolan). URL: http://www.mecheng.adelaide.edu.au/cdoolan/ (C.J. Doolan).