Author(s): Hallie Thornburrow, Paul Rodrigue, Vincent H. Chu
Linked Author(s): Vincent H. Chu
Keywords: Computational Fluid Dynamics (CFD), drop shaft, energy dissipation, air entrainment, residence time
Abstract: A drop shaft is typically characterized by a vertical connection between two pipes at different elevations which facilitates the conveyance of water from one elevation to another. The hydraulic analysis associated with the design of a drop shaft is complex due to the entrainment of air, the loss of energy throughout the structure and the region where the water jet enters the lower pool. A poorly designed drop structure can lead to drastically reduced lifespans of the structures caused by erosion, in addition to very serious safety concerns. Smaller scale physical models have been used to develop the hydraulic design criteria associated with these structures and predict flow patterns of various designs. This procedure is very expensive and time consuming, particularly if modifications are required, even if the modifications are minor. This research compares the physical model of a drop shaft with a computational fluid dynamics (CFD) model of the same structure. The physical scale was completed by Hubert Chanson. The flow regime simulated by these models consists of a free jet which emanates from the inlet channel and hits the opposite wall. This jet travels vertically down the opposite wall creating a �film� or a curtain in front of the outlet pipe. Results of this work show that when identical inflow conditions are set, very similar flow behaviors, water levels and hydraulic residence times results were produced by both types of models. This suggests that CFD software can be used as a tool to evaluate drop shaft model designs. All the salient data sets produced from the Chanson's work could be duplicated. In addition, other information can be extracted from the CFD model such as air content, pressure, velocity at any point throughout the flow regime
Year: 2017