Development Of High-Fidelity Viscous Numerical Wave Tank

Numerical wave tank(NWT) is an essential approach to study water wave problems,where the viscous NWT based on Navier-Stokes equations ensures the most faithful reproduction of the physical wave tank through its ability to capture the relevant flow details.The usage of 1st and 2nd order accurate methods,however,imposes strict criteria for the time step and mesh resolution with the aim of reducing the unphysical damping caused by numerical dissipation.Refinement in temp-spatial resolution will indisputably lead to an increase in computational time and the resulting high cost is now a major impediment to the development of this type of NWT.In order to develop a more efficient NWT for viscous flow studies,a high-fidelity model is employed as the two-phase flow solver and the performance of the present NWT is systematically examined in this work.An NWT is built based on a Navier-Stokes model,which employs the VPM(volume-average/point-value multi-moment)scheme as the fluid solver and the THINC/QQ method(THINC method with quadratic surface representation and Gaussian quadrature)for the free-surface capturing.To facilitate more accurate convection calculations,time stepping of the advection term,as well as the volume-of-fluid transport equation,is handled with the third-order TVD Runge-Kutta scheme in the present model.For wave generation,a mass source function is applied in this work.By positioning the wave-maker inside the solution domain,wave damping can be straightforwardly applied to all domain boundaries,wave reflections from the tank walls and internal structures can thus be eliminated in simulations.Simulations of regular waves in intermediate water depth are conducted and the performance of the present model and interFoam solver(a widely used solver within OpenFOAM package) in simulating the wave propagation is systematically compared in this work.The results clearly demonstrate that compared with interFoam solver,the present model significantly improves the dissipation properties of the propagating wave trains.It is also shown that the present model requires much less computation time to reach a given error level in comparison with interFoam solver.The interactions between a solitary wave and a submerged barrier are investigated in this work as well.The simulations fit fairly well with experimental measurements in terms of free surface motion,velocity profiles,vorticity fields,and wave force.In addition,it is shown that the present model captures a number of experimental details of sub-grid resolution,including highly distorted surface and splashed droplets.A super NWT that has a length of 300 m is built for the investigation of long-term evolution of a nonlinear wave train in deep water.Some significant behaviors observed in physical experiments,including the near recurrence of the initial state,unstable wavefront,and permanent frequency downshift,are reproduced in the simulations.Whilst in its development phase,the present NWT highlights its advantages in numerical dissipation property and accuracy of free surface capturing through the preliminary results shown in this work.Together with its reasonable cost and fair robustness,the present NWT has the potential to work as a powerful numerical tool for the study of water wave problems in the future.