Numerical modeling of large-scale dam breach experiment

Abstract

This paper presents the analysis of an earth dam breaching process which incorporates an analytical erosion model into CFX in ANSYS to calculate the rate of erosion in order to capture the kinematic characteristics of dam breach. Based on the water level and the storage capacity of the reservoir on the upstream side of the dam, the discharge of water over the dam can be calculated. The discharge of water is also used to validate the results from the numerical simulations. The height of the experimental dam during the breaching process is calculated using an empirical relationship based on the water level, the discharge rate, and the width of the breach. A particle-scale progressive scouring entrainment model has been incorporated into CFX in ANSYS to calculate the rate of erosion which is used to simulate the development of the breach. When comparing with field observations, the root-mean-square error (RMSE) between the calculated and measured surface velocities is equal to 0.37 m/s, indicating a discrepancy of 16%, and the RMSE of the calculated and measured discharge is equal to 1.13 m3/s, showing an average discrepancy of 19%. Additionally, the numerical results are validated by comparing the calculated and observed water levels in the breach and the calculated and observed width of the top of the breach. The RMSE between the calculated and observed water levels in the upstream of the dam (hup), the water level in the center of the breach (hc + hd), and the width of the top of the breach (BT) are equal to 0.026 m, 0.095 m, and 0.44 m, respectively, which show average discrepancies of 1%, 4%, and 13%, respectively. This dam break experiment is a unique full-scale experiment for the evaluation of numerical and analytical models. This research shows that the erosion model incorporated into CFX is able to capture the main characteristics of the dam failure process. The incorporation of the erosional model into the dam breach analysis can be used to analyze the failure process of barrier dams.