Potential Flow From a Tapering Nozzle Impinging on a Flat Plate

Abstract

A perfect flow from a two-dimensional nozzle is considered discharging against a normally placed flat plate. Particular attention is given to the effect of the angle of the nozzle, and results for angles of 15, 30, 45, and 60 deg are compared with those for a parallel-sided orifice. This model can be regarded as a two-dimensional representation of a plate valve or flapper valve in which the flow does not reattach to the land of the nozzle. The variations of the back pressure and the contraction coefficient with valve aperture have been plotted, and the shape of the free streamlines and the pressure distribution on the plate have been found. By considering the effect of fluctuations far upstream, the flow in a tapering orifice is shown to be inherently more unstable than that in a parallel-sided orifice. It is also shown that the control of the valve aperture over the back pressure is better in parallel-sided orifices than in angled ones.