Surface source model for confined flow past a circular cylinder in a symmetrical configuration

Abstract

Aerodynamic tests of rigid bodies and structures are usually carried out in wind tunnels using scale-down models under controlled flow conditions. Presence of the tunnel walls causes the test conditions to deviate from the free-flow condition of the prototype. Therefore, a correction procedure is needed for the results of the model experiment to predict the actual performance of the prototype. This paper presents a surface source model to evaluate the effects of wall interference in the case of incompressible flow around two- dimensional circular cylindrical structures under symmetrical configuration. The effect of the body and its wake on the oncoming flow is modelled by a surface source distribution over the front wetted surface. The confined flow is then mapped to a transformation plane where the flow field is relatively simple to analyse. The flow pattern, surface pressure distribution and the drag coefficient at a given blockage ratio are predicted. Satisfactory agreements between the calculated values of the present model with the available experimental data for a range of blockage ratios at sub-critical Reynolds numbers verify the validity of the model. Based on the present theoretical results, a new correction formula of the wall effects for the mean drag coefficient is proposed. The most significant advantage of the present model over the other models is that no empirical information is needed for the analysis.