Generalized Contraction Coefficient of an Orifice for Subsonic and Supercritical Flows

After a brief historical review of the pertinent literature, expressions are developed which approximate the compressible contraction coefficient of any orifice in any installation for both subsonic and supercritical flows. These coefficients are based on a presumed knowledge of the incompressible contraction coefficient for the same orifice. Included in the formulations are compressibility effects upstream and downstream of the orifice as well as velocity-of-approach effects. Comparisons between the suggested approximations and recent experimental data are made.