2D Numerical Simulation on the Local Scour Pit Downstream of Hengdan Hydropower Station

A two-dimensional model was adopted to predict downstream scour pit of Hengdan Hydropower Station discharge structure with regard to its shape and maximum erosion depth. Based on flow field simulated, the flow shearing stress on pit bed during scour process was calculated using the developed code. By comparing the flow shear stress and the incipient motion drag force, it could be judged whether bed sediment was in incipient motion or staying on riverbed, and the riverbed surface form could also be predicted accurately. Herein, dynamic mesh was applied to adapt to shifty bed surface corresponding to updated flow condition. Simulation results indicate that the developed model could give good predictions to scour pit in terms of its morphology and depth, which were in line with the results obtained from physical model experiments. At the initial stage of scour, shear stress on pit bed decreasing rapidly, and then it dropped slowly. This is in accordance with the predicted scour speed tendency. © 2017, The Editorial Board of Journal of Basic Science and Engineering. All right reserved.