The Effect of Inlet Width on the Performance of Retention Ponds in Thermally Induced Flows

The effects of inlet and outlet configurations in sediment retention ponds (SRPs) have been widely investigated by a number of researchers; however, the challenges associated with the proper inlet and outlet design still exist when considering temperature differentials in the ponds. The buoyancy forces are arising from differences in temperature potentially changing the flow in the pond by forming density currents. Changing outlet configurations will not solve the issues associated with density stratified flows while the careful design of the inlet can predominantly control the density currents. This study evaluates the effects of different Inlet width ratios (IWRs) on the flow pattern and residence time in a sediment retention pond when inflow is colder or hotter than the water in the pond. In this research, an innovative experimental setup was used to create the temperature differentials. The physical model is a trapezoidal pond made from transparent acrylic sheets fitted on a steel frame with dimensions of 4.1 m × 1.6 m and is 0.3 m deep, and a bank slope of 2:1. The rig was designed so that the temperature differentials could be created using two separate systems in which each system consists of a heat exchanger unit to change the temperature of the water.

The results reveal that in cold influent test cases increasing the inlet width to 100% of the total width of the pond could effectively increase the performance of the pond while in hot influent cases decreasing the pond width to 30% the total width of the pond could successfully improve the performance of the pond.