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Article

Experiments on a bluff body wake with varying inlet conditions

Authors: Fallenius, B. E. G. , Fransson, J. H. M.
Document Type: Conference
Pubstate: Published
Journal: Svenska mekanikdagarna, Göteborg, June 13-15 2011
Volume: 1   73
Year: 2011

Abstract

In this pro ject the aim is to experimentally study the instability of wakes behind bluff bodies from a fundamental research point of view, both for the natural case as well as with various wake flow control methods applied. This is realized in a new experimental setup specially designed to perform parameter variations [1], which are most often not possible in usually fixed experimental geometries. The present bluff body is a so-called rectangular-based forebody with permeable surfaces on both sides, enabling suction or blowing of air through the surfaces, cf. figure a) for a sketch. This gives the unique possibility to vary the thickness and the shape of the boundary layer pro?les along the forebody, while keeping the free stream velocity constant, which is illustrated in figure b). Furthermore, there is a threshold suction level from where on the shape of the pro?le will not change, this is the well known asymptotic suction boundary layer (ASBL) which has a constant thickness independent of the free stream velocity, cf. figure c). Note that these profiles have both a constant boundary layer thickness and a constant shape factor. Consequently, the initial conditions of the wake flow can be altered as shown in figure a). The suction or blowing can either be uniform or local, and since the two sides are independent of each other asymmetric wake pro?les may also be generated. How the di?erent parameters a?ect the wake flow instability and the structures therein is the subject of the present investigation.