Hydrodynamic Behaviors Of Waves Interaction With Porous Medium

In coastal and offshore engineering, problems on interaction of water waves and porousmedium are often encountered and difficult to deal with. So it's significant in theory and greatapplied value of coastal and offshore engineering to research the problem. The flume test andnumerical model are used to study the propagation of water waves over a permeable bed, asubmerged porous breakwater, and interaction of water waves-rubble moundbreakwater-seabed.At first, a coupling model of wave interaction with porous medium is established. Thewave field solver is based on the two dimensional Reynolds Averaged Navier-Stokes (RANS)equations with a k-εclosure. A piston-type wave maker is set up in the computational domainto produce incident waves and the free surface is traced through the PLIC-VOF (PiecewiseLinear Interface Construction-Volume of Fluid). Forchheimer Equations adopted in porousflow within the porous media. By introducing a Velocity-Pressure Correction Equation forthe waves and porous flow, highly efficient coupling between the two flows is realized. Thetwo flows can be solved simultaneously and no boundary condition is needed on the interfacebetween them. The implicitly limitation of Continuity Equation makes it sure that the velocityand pressure of the two flows on the interface keep to equal at any time. Biot's equations havebeen applied to solve the sandy seabed, and the u-p finite element formulations are derived bythe application of the Galerkin weighted-residual procedure.The evolution of an initially flat sandy bed is studied in a laboratory wave flume undercnoidal wave and acoustic Doppler velocimeter (ADV) was utilized in the detailed velocitymeasurements at different positions. The formation and the evolution of ripple have beenanalyzed by CCD images and the asymmetric rippled bed is induced by nonlinear wave flow.The flow structure and a complete process of vortex formation, evolvement and disappearancewere observed on the asymmetric rippled bed under cnoidal waves. The numerical model wasused to investigate the flow structure and vortex in the asymmetric rippled bed under theaction of the cnoidal wave. Based on the experiment and calculation results, sinusoidal andcnoidal waves induced pore pressures in free seabed are examined through parametricanalysis. It suggests that wave-induced pore water pressure increases with increase of waveheight and period, reduces with increase of the depth of water. Permeability and thickness ofsand bed are the more important factors influencing the pore-water pressure. Cnoidal wavesinduced pore pressure is more nonlinear than sinusoidal waves. It is found that thewave-induced pore pressure is more significant affected to sand transport. The coupling numerical model is used to study sinusoidal and solitary wave interaction with scree seabed.The numerical tests are conducted to study the effects of seabed thickness, particle diameter,porosity, intrinsic permeability and slope on wave damping and pore pressure distribution, alsoanalyzed velocity fields.The coupling numerical model is used to study the interaction between water waves andsubmerged porous breakwater on flat and slope bed. The influences of breakwater height,width and porosity on transmission coefficients are analyzed. The vortex around thebreakwater is also investigated. The velocity field in and out the breakwater has been carriedout, and also compared velocity field around the submerged permeable and impermeablebreakwater on the slope bed.The paper examines the problem of wave-seabed-rubble mound vertical breakwaterinteraction from flume test. Based on the experiment result, the wave induced pore pressurearound a vertical breakwater will be examined through a parametric analysis. In the paper, aweak coupling numerical model is developed for the study of the nonlinear dynamicinteraction between wave-rubble mound breakwater-seabed. The continuity of the pressure onthe interface between fluid and porous medium domains is considered. Laboratory tests wereperformed to verify the proposed numerical model, and it is show that the pore-waterpressures and the wave heights computed by the models are in good agreement with theexperimental results. It was found that the proposed model is effective to predict theseabed-nonlinear wave interaction and is able to handle the wave-breakwater-seabedinteraction problem. The model is used to discuss the hydrodynamic characteristics around therubble mound breakwater.