DISCHARGE CHARACTERISTICS OF SKEW SIDE WEIR

Abstract

Side weirs are diversion structures widely used in irrigation engineering .A side weir is an overflow weir constructed framed in the side of the channel over which lateral overflow takes place when the water surface in the channel rises above the weir crest skew side weir is a side weir which is skewed with respect to the side of the main channel, that is it makes an angle a. with the side of the channel. For the computation of side weir discharge De Marchi equation is commonly used. The discharge coefficient employed in this equation have been related by various investigators to the main channel upstream Froude numbers F11 only without considering. Other variables like weir height, channel slope, channel roughness, channel bed width etc., which affect the side weir discharge. Further, inspite of their great practical importance, little attention has been given to the study of flow over sharp crested skew side weir at various angles. In the present investigation, the discharge characteristics of sharp created rectangular skew side weirs have been studied by undertaking a systematic experimental program involving wide variation in head to weir height ratio and side weir skew angles. The skew side weir discharge was computed using the concept of elementary discharge coefficient and integration of spatially varied flow equation over the side weir length .The equation for the elementary discharge coefficient of side weirs with different skew angles were obtained by minimizing the absolute error between the observed (experimental) skew side weir discharge and computed side weir discharge using the grid search optimization technique. A generalized equation for elementary discharge coefficients for all skew angles was then developed.