Supercritical Flow in Rectangular Expansions

In recent years, the occasions for design of channels to contain supercritical flow have increased considerably. A need has developed for a method of predicting the physical characteristics of such flow based on theory. Use has been made of the analogy between supersonic gas flow and supercritical fluid flow to apply the method of characteristics, originally developed for gas dynamics, to fluid mechanics. The writers have checked experimentally the validity of the assumptions made by Bagge and Herbich in the analysis of supercritical flow passing through a rectangular expansion. An experimental model was constructed in the laboratory and the resultant surface profiles obtained for different sets of parameters compared to those predicted by the mathematical model. Results indicated that the assumptions of frictionless flow and negligible velocity perpendicular to the bed of the channel were too important to be neglected. Several graphs comparing theoretical profiles with those obtained in an experimental model are presented.