Large-eddy simulation of turbulent open-channel flow with free-surface fluctuations

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732Large-eddy simulations of open-channel flows with free-surface fluctuations have been conducted. The conventional HSMAC algorithm of Hirt & Cook(1972) is extended to incorporate the calculation of the motion of the free surface within the iteration cycle for computing the pressure and the velocity using the kinematic and the dynamic conditions to be satisfied on the free surface. This method of computing a moving free surface has been verified in a benchmark of two-dimensional standing wave flow. For the sub-grid scale model, the standard Smagorinsky model with near-wall damping is used. Its performance is verified in a fully developed open-channel flow over a smooth flat bed at a laboratory Reynolds number. Subcritical flow past a sudden drop is then simulated and the results indicate that the mean velocity distribution can be predicted very well but the turbulent stresses need improvement