SUBCRITICAL FLOW OVER RECTANGULAR SIDE WEIR

Side weirs are flow-diversion devices widely used in irrigation. land drainage, urban sewage systems and so forth. For computation of side-w eir discharge, the de Marchi equation is widely used. Using de Marchi' s equation, various investigators have related the weir discharge coef ficient with the main channel's upstream Froude number, Thus, the domi nant variable ratio of head to weir height has not been considered in previous investigations. Presented herein is a concept of elementary d ischarge coefficient for the discharge of an elementary rectangular st rip along the weir crest. Like that of a normal weir, this elementary discharge coefficient has been related to the head weir height ratio o nly. Using this relation, a methodology for determination of the weir discharge is described.