Analytical Determination of the Discharge Characteristics of Cylindrical-Tube Orifices

Abstract

Rational expressions for the incompressible discharge characteristics of square-edged cylindrical-tube orifices having axial lengths of the order of one diameter or greater are derived by the application of boundary layer theory to a simplified model of the flow mechanism. The theoretical predictions of discharge coefficient value and of cavitation inception in the case of liquids are shown to accord well with available experimental data. The effects of chamfered and radiused entry are discussed. This new analysis is intended as a step towards the goal of establishing the means of deriving optimal orifice designs in the fields of flow measurement, servomechanisms, fuel injection, pneumatic gauging, and in other domains.