Numerical Simulation And Experimental Study of Hydraulic Performance of Circular Crested Normal Weirs

Abstract

Weirs are simple control structures usually built across channels for water storage and measurementof flow rates. The main target of the present study is to numerically simulate and experimentally study thehydraulic performance of circular crested normal weirs. For numerical simulation, the commercialpackage ANSYS CFX is utilized adopting tetrahedrons mesh with a maximum total number of 1932301elements, while, for the experimental study nine physical models are manufactured and tested havingdifferent crest diameters and various weir heights. Numerical simulation results demonstrated that theANSYS CFX software is highly capable for simulating circular crested normal weirs showing quite goodagreements in water surface profiles and 4.3% mean percentage error in upstream head above crest,while, the software showed 6.8% mean percentage error in estimating discharge coefficient. A simpleempirical expression is obtained for the estimation of coefficient of discharge in terms of ratio of upstreamhead to weir height and the ratio of upstream head to crest diameter with a coefficient of correlation =0.88. The flow rate magnification is found increasing with the increase of upstream relative head and thebest performance of the weir is found when the ratio of crest diameter to weir height = 0.33 at which thehighest increase in flow rate is observed ranging between 25.41% and 32.14% compared with sharpcrested weirs having the same height and the same length of crest