The efficiency of transpiration flow through perforated plate

Abstract

The interest in transpiration flows through perforated walls is recently increasing again because the manufacturing of such walls is much easier than in former decades. Recently the interest is related to laminar wing technology and effusive cooling in aeroengines. Transpiration flows become useful also for other applications as reduction of separation and other flow control devices as passive shock wave boundary layer control.Plates perforation used for the mentioned above flow control application is rather low at the level below 10%. In order to minimize the flow disturbance small hole diameters are used, well below 1 mm. This means that there is a large number of holes, which cannot be directly included in the numerical simulations. Therefore physical model is still necessary to serve as boundary condition at perforated wall. Several models have been offered formerly with limited success.In the present paper a new model is proposed, which is able to incorporate whole pressure drop range from weak pressure differences to chocking conditions. To create and verify the model experimental investigations as well numerical simulations were taken into account. As the quality of holes has important impact on the plate aerodynamic performance, the model introduces plate effectiveness coefficient. This coefficient allows to take into account perforation quality.