Three-Dimensional Numerical Study of Dam-Break Flood Impacting Problem with VOF Method and Different Turbulence Closures

In flash flood events, predicting the impact loads of rushing water is helpful to detect the possible and direct damage to the downstream structures. The present study conducted three-dimensional numerical simulations for three typical laboratory experiments with emphasis on the hydrodynamic impact. Two RANS-based k-ε models and the LES model were chosen for the turbulence closure. The VOF method was applied to track the free surface. The numerical model provided satisfactory results of the temporal variations of both water depth and hydrodynamic load, which are in great agreement with the experimental data. Further quantitative comparisons also show that the deviations between simulations and experiments are small. The values of performance indicators mean-absolute deviation (MAD), root-mean-squared deviation (RMSD) and mean-absolute percentage deviation (MAPD) are respectively lower than 0.05 (0.03 m), 0.08 (0.048 m) and 19% for depth prediction, lower than 0.05 (0.03 kPa), 0.11 (0.06 kPa) and 11% for pressure prediction, and lower than 0.7 N, 1N and 15% for net force prediction. The absolute values of relative percent deviation (RPD) are less than 27% and 25% for the prediction of peak pressure and peak net force, respectively. The values of Nash–Sutcliffe efficiency (NSE) for depth and pressure are higher than 0.8. Moreover, the impulse of pressure or net force exhibits better predictability than its instantaneous values. Additional investigation shows that the time-varying behaviour of the impact force are significantly affected by the upstream initial depth, and the maximum impact force has a quadratic relationship with the initial depth.