Development of a numerical wave-current flume using the LES model.
Zhenshan Xu, Yongping Chen
Thursday 2 july 2015
17:00 - 17:15h
at Oceania (level 0)
Themes: (T) Water engineering, (ST) Computational methods
Parallel session: 13E. Engineering - Computational
The interaction between wave and current could affect other important processes in the coastal area, such as the effluent diffusion and its transportation, the suspension and transportation of sediment, etc. It has been extensively studied by coastal engineers and researchers since 1970s. The mean properties, such as the deviation from the log-law of the time-averaged velocity profiles, were found both experimentally and numerically by many previous investigators. However, the research on the turbulent properties was mainly revealed by the experiments, lack of the numerical simulations. In this study, a large eddy simulation (LES) model is developed based on the spatially filtered Navier-Stokes equations to simulate the interaction of wave and current. A dynamic sub-grid scale model is used to close the turbulence equations. A so-called Lagrange-Euler Method is applied to solve the free surface problem. The numerical solution procedure is split into three steps, i.e. advection step, diffusion step and propagation step. Both the wave parameters and the current velocity are given at the inflow boundary, while the radiation condition combined with a sponger layer is imposed at the outflow boundary to mitigate the numerical reflection. At the bottom boundary, the wall function of log-law is specified at every diffusion step to simulate the influence of the roughness height. The simulations of the current flow, wave propagation, and the wave following current are performed. The results of the pure current (mean velocity profile and turbulent intensity) and pure wave (free surface and phase-averaged velocity profile) agree well with the experimental data. The numerical simulations with the given input parameters, including wave period, wave height, current velocity constant and the roughness height, could quantitatively reproduce the larger velocities near the bed and smaller velocities above a certain depth in the combined mean flow of the wave-following-current, which are consistent with the experimental findings. Further, the distribution of the turbulent intensities and Reynolds stresses along the water depth in the wave-current flow is presented. The influence of the turbulent inflow velocity conditions on the Reynolds stresses is also considered.
