Experimental and Numerical Study of Flow Near Free Surface Intake

A water intake is normally used to divert water from the main canal and river for various purposes like domestic water supply, irrigation etc. Flow in the intake are complex on account of flow separation phenomenon occurring at the intake junction. The intakes are usually installed at right angles to the main channel flow direction, which produces a large separation zone inside the intake and reduces flow discharge. In this paper both experimental and numerical study has been carried out for velocity profiles ,water surface contour observations,depth of flow at various section and separation zones occurring in 45 degree lateral surface intakes.High precision measurement of velocity has been done by using 16-MHZ ADV (Son Tek).Computational fluid dynamics (CFD) simulationusing FLUENT SIMPLEk- ε model has been done along with Grid independence study and the results has been compared with from experimental observations. The result shows that measured and calculated velocity profile are in close agreement with each other. However,the model slightly under-predicts the measured velocity profiles near the free surface, reproduces them with remarkable accuracy at most locations at the intermediate level and over predicts them somewhat near the channel bed.The size (Length and width) of the separation zone in the intake channel was found to decrease with increase in the discharge ratio(the discharge in the branch channel to the main channel).The location of the separation zone moves from upstream to downstream at the mouth of the water intakewhen compared to the separation zone at the 90 degree and 45 degree intakes.