Numerical Study of Sedimentation and Flow Pattern at the Open Channel Intake

Abstract

Generally, open channel lateral intake structures are extensively used in the water and environmental projects. The passing flow at side intakes is mostly turbulence containing vertical and horizontal spiral currents causing sediment problems. The flow separation region in the intake channel is critical for sediment and water distribution during the diversion. It denotes a large reduction in the possible breadth of the lateral branch's incoming flow, as well as a place where sediment has collected, obstructing the deviated flow. This study aims to reduce and control sediment problems at the lateral intake by improving the flow pattern at this area using three-dimensional numerical models simulated in CFD, ANSYS Fluent software. The correctness of the three-dimensional numerical model was validated by a previous experimental study that showed good accuracy. Different discharge ratios and a range of shape designs were used to simulate the flow pattern at the intake channel junction. The findings demonstrated that the separation zone measurements minimize as the discharge ratio increases. Based on the changing the intake entrance shape results, cutting the outer boundary of the canal entrance widens the separation area, as well as an additional separation spot as the cutting size grows. In contrast with the internal chamfered angle models of the intake inlet, the separation area dimensions are reduced. The chamfered and rounded inner intake edge model with 30o angle to the main channel flow direction and the length of the chamfered side that normal to the flow direction (c value ) equal to three-quarters of the intake width was noticed to be the best design for lessening separation extent in this study. Thereby, the reduction ratio of the separation area width and length reaches in this case to 90% and 72%, respectively.