Blockage Effects on Two-dimensional Bluff Body Flow

Abstract

SummaryThe time mean flow past a two-dimensional bluff body in a wind-tunnel is modelled by an adaptation of the numerical free-streamline method of Bearman and Fackrell. Provided the base pressure and separation positions are specified in advance, the method allows the calculation of the flow field outside the wake and in particular of the pressures on the wetted surface of the body. Good agreement of the predicted pressures with experimental results is obtained for a flat plate, wedge and circular cylinder at various blockage ratios. In addition to predicting the confined flow, it is shown that a free-air base pressure can be simply deduced from the confined base pressure. With an assumption that the separation positions are unaffected by blockage, this allows the free-air flow field to be calculated. By using an analogy to Roshko’s Strouhal number, which has been found to be invariant under constraint, a free-air Strouhal number can also be deduced.