Author(s)

S. Heng, T. Tingsanchali & T. Suetsugi

Abstract

The objectives of this research are to (1) analyze and select the most appropriate existing formulas for predicting maximum scour depth (DS) and impact location (LS) of a local scour hole in the plunge pool below a chute spillway with flip bucket, and (2) establish a new DS method functional with the easily available data, discharge (Q) and tailwater depth, based on experimental results. The experiment was conducted with the Nam Ngum 3 spillway physical model. Each DS and LS formula has its own limitation and therefore does not perform well with different ranges of Q. For DS prediction, the combined method of Mason-B (for low Q), Taraimovich (for medium Q) and Mason-A (for high Q) was found to provide high accurate results with Nash-Sutcliffe Efficiency (NSE) of 0.99, root mean square error (RMSE) of 1.84 m and mean absolute percentage error (MAPE) of 3.86%. Similarly for the case of LS, the combined method of Kawakami-Taraimovich (for low and high Q) and Elevatorski-Taraimovich (for medium Q) is the most ideal technique. By using dimensionless analysis, the new DS formula was established and its statistical performance indicated by NSE, RMSE and MAPE is 1.00, 0.97 m and 2.35%, respectively. The coupled approach of Mason-B, Taraimovich and Mason-A is recommended when there are sufficient input data because many factors are associated and thus high accurate results are expected. However, in data-constraint situations, the new DS formula would be more feasible. Keywords: maximum scour depth, impact location, local scour hole, plunge pool, chute spillway with flip bucket, numerical method, physical model.

Keywords

Keywords: maximum scour depth, impact location, local scour hole, plunge pool, chute spillway with flip bucket, numerical method, physical model.