Numerical Study On Vertical Turbulent Jet In Waves And Currents

Ocean wasterwater discharge system is the main tendency for modern coastal city to dispose wasterwater. But there are few studies on mixing and advection of pollutant in wave environment with turbulence model. Based on former research work, a 2D vertical turbulence model and a 3D turbulence model are developed with nonlinear k-s with VOF method, which are good at simulating the mixing and advection of pollutant in waves and currents, where the free surface has big fluctuation. Based on the 2D vertical turbulence model, the diffusion coefficients in waves and wave-currents are studied. Based on the 2D and 3D model, the distributions of velocity field and concentration field of jet in different environments are simulated and analyzed in this paper.The free surface should be traced when the natural water body is simulated. Tracing free surface accurately is very important when wave is considered for the big fluctuation of the free surface. Turbulent vortices exist in the whole water body with flow. The flow fields of jets interacting with waves and currents vary violently with anisotropic character. VOF method which can be used to trace free surface accurately without needing large computation time and storage, and the nonlinear k-s turbulence model which can be used to simulate anisotropic flow, are choosed to develop the numerical models. In the models, the three layers wall function method is used near the solid walls, the free surface boundary condition of turbulent varies are set to promote the stabilization, and the improved sponge layer is used at the outflow boundary. The models are validated by comparing the free surface, velocity, concentration and turbulent viscosity coefficient between the results of simulations and experiments.Pollutants will be passively advected and dispersed in water once be discharged into water and go beyond the initial active entrainment phase. And the scale of pollutant is far greater than the particle kinematic amplitude with wave. So in this region pullutans advection and diffusion could be resolved with wave phase everaged flow. Then getting accurate diffusion coefficient is one of the key steps. Based on simulation results of many cases with different depth of water, velocity, wave height and wave length, the diffusion coefficients in wave and wave-current are studied and fitted equations are generalized.Vertical plan jets in static water, in currents and wave-currents are simulated and analyzed. In static water, the distributions of the velocity field, the free surface, and the decay of the axis velocity are analyzed. In currents, the relationship between reflux shape and its...