An Improvement in the Treatment of Separation in General Cascades by Potential Flow Methods

Abstract

It is assumed that, when the flow over the surface of an aerofoil in cascade undergoes separation, the pressure (or reduced pressure for a rotating circular cascade) remains constant aft of that point. In the present treatment, as in a previous method, this condition is maintained by the imposition of a source sheet along the appropriate surface of a thin aerofoil. In contrast to the previous method, the correct kinematic condition is maintained by the imposition of a correcting vortex sheet along the camber line. In this way it is possible to allow for the presence of separation on either or both surfaces; the vortex sheet is determined from the numerical solution of an integral equation of the first kind. The theory, valid in incompressible flow, is applied to an axial cascade and to a radial impeller and a comparison is made with the measured velocity distribution and displacement thickness.