Effects of randomly spaced, non-uniformly sized roughness elements on the flow structure and energy loss in a supercritical open-channel flow were investigated using numerical models and compared with experimental data. A three-dimensional numerical model for complex flow simulations was evaluated using experimental data. Simulations were performed at large Froude numbers varying from 2.5 to 2.8. The overall nature of the water surface profile was well simulated but a maximum of 30% error in water level was noticed closer to the roughness elements. The simulated velocity profiles matched well with the observed data in the upstream locations of roughness elements but a minor discrepancy was observed in the wake region (downstream side) near to bed. The numerical model did not accurately resolve the local flow features such as the heights and lengths of water jumps over obstacles. The maximum difference between the observed and predicted jump lengths was 73.4%. However, it satisfactorily simulated the general flow features, including the total energy loss.

Full text