Development And Application Of Numerical Wave Flume Based On OpenFOAM

After entering the 21 st century,because of the changes in the international situation,the shortage of land resources and other factors,the level of the China's attention to the ocean has gradually increased.In the field of the ocean engineering,there are three methods for scientific research: theoretical derivation,model test and numerical simulation.In the past 20 years,with the rapid development of computer technology,numerical simulation has gradually become a more mainstream research method.A proven mathematical model will not only save costs,but will also greatly reduce the workload.Under these conditions mentioned above,this paper develops a numerical wave flume program DUTFoam based on OpenFOAM and uses this program to simulate the typical problems in ocean engineering.The two-phase incompressible CFD solver InterDyMFoam,which solves the Reynolds time-averaged equation(RANS)has been selected as the platform during the process of development.The solver uses the VOF method to track the free surface,and uses the PIMPLE algorithm to decouple the velocity and pressure.In addition,InterDyMFoam is a version of dynamic mesh.The way to solve the governing equations is almost the same as that of InterFoam.The development of the program in this paper involves three modules: wave generation,wave absorption,and porous media flow.These will be elaborated as follows:Two wave generation methods are involved in the program.The first one is the method of moving wall wave generation.It just likes the piston-type wave-maker in the lab.A class with the name of tuibanWaveGeneration has been developed by means of class inheritance.This class calculates the boundary equation of motion based on the input wave parameters and passes it as a Dirchlet condition to the wave generation boundary.This method does not have any exchanges of physical quantities at the boundary,which means strictly guarantees quality conservation.The second one the method of mass source wave generation whose the principle is similar to an underwater explosion.The fluctuation of the fluid is caused by the input and output of the mass in the specified area.Both wave generation methods could handle the simulations of various waves,such as regular waves,random waves,focused waves,solitary waves,and wave groups.All of the wave simulation results in the paper have been compared with theoretical or experimental values and the good accuracy has been found.The wave absorption module consists of two parts with the name of the active absorption system and the damping layer method,corresponding to the absorption of the secondary reflection wave and the reflected wave,respectively.In the active absorption system,in every time step,the change of the free surface is calculated by the dry-wet boundary method,and the difference between the numerical and theoretical value is fed back as a control signal to realize the motion of the wave paddle.In the damping layer method,a source term is added to the momentum equation to absorb the wave.Four different forms of attenuation functions have been employed to provide a wide range of applications,which can effectively absorb the reflected waves at the end of numerical wave tanks and ensure the accuracy of calculations.The porous media flow module is mainly developed for some special structures in the actual project,such as the foundation bed of the dock.In the porous media region,the volume-averaged Reynolds time-average equation(VARANS)is used as a governing equation.This equation is derived from Darcy's law and could better simulate the propagation process of fluids in porous media.Through comparison with the physical model test results,the accuracy of the module is validated,and a typical example of its simulation also achieves better results.The simulation of various waves shows that DUTFoam has high accuracy and good ability of wave generation.Simulations of typical problems such as wave runup,interaction between waves and structural show that DUTFoam has a good ability to handle the non-linear problems in ocean engineering.