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-weir discharge, the de Marchi equation is widely used. Using de Marchi's equation, various investigators have related the weir discharge coefficient with the main channel's upstream Froude number, Thus, the dominant variable ratio of head to weir height has not been considered in previous investigations. Presented herein is a concept of elementary discharge coefficient for the discharge of an elementary rectangular strip along the weir crest. Like that of a normal weir, this elementary discharge coefficient has been related to the head weir height ratio only. Using this relation, a methodology for determination of the weir discharge is described.