ANALYSIS OF SIDE WEIRS AND SLUICE GATES

Abstract

Side weirs and side sluice gates are diversion structures widely used in irrigation engineering. A side weir is an overflow weir framed in the side of a channel over which lateral outflow takes place when the water surface in the channel rises above the weir crest. A side sluice gate is an opening in the side of a channel through which lateral outflow takes place. For computation of sharp crested side weir discharge De Marchi equation is widely used with a constant value of discharge coefficient. Various investigators have proposed different equations relating the weir discharge coefficient to the main channel upstream Froude number F only. The predicted side weir discharge based on these equations will be markedly different for the same values of F This is evidently so due to the fact that other variables like weir height, channel slope, channel roughness, channel bed width etc., which affect the weir discharge have not been considered by these investigators. Further, inspite of their great practical importance, little attention has been given to the study of flow over broad crested side weirs and through side sluice gates. (i) In the present study, the concept of a discharge coefficient for an elementary strip along the length of side weir or side sluice gate is introduced. Equations of the elementary discharge coefficient for various shapes of side weir and rectangular side sluice gate have been obtained. A common methodology involving the solution of the proposed Elementary discharge coefficient equation and the spatially varied flow equation has been evolved for the prediction of discharge and flow profile along the diversion structure. (