Drag on flat plates of arbitrary porosity

A new model for the drag force on a two-dimensional flat plate of arbitrary porosity, oriented normal to the free stream, is introduced. The model is an extension of that introduced by Koo & James (J. Fluid Mech., vol. 60(3), 1973, pp. 513-538), where the performance at low porosities is improved by including a base-suction term. The additional drag due to the base suction is calculated implicitly using momentum theory, which makes the model self-contained. The model predictions exhibit convincing agreement with experimental observations over a wide range of porosities, including the solid case, as long as shedding is absent or suppressed.