Numerical Simulation Of Piston-type Active Absorption Wave Making Based On OpenFOAM

With the development of computer technology and the progress of computational fluid dynamics theory and method,numerical simulation has become an effective tool to study waves and the interaction between waves and buildings.Among many CFD software,open source software OpenFOAM is favored by scholars because of its good scalability,stable and powerful underlying class library and rich pre-processing and post-processing interfaces.Using the moving boundary for numerical wave making can approach the motion characteristics of the actual wave making plate as much as possible,so that the numerical simulation and physical wave making can be combined.The two verify each other and promote the continuous development of wave making technology.The numerical pool is a limited scale water area.The reflected wave from the domain will form a secondary reflected wave at the wave making plate.If the secondary reflected wave is not processed,the wave will be reflected and superimposed repeatedly in the water area,which will seriously reduce the accuracy and stability of the simulation.Therefore,the active absorption technology that can effectively eliminate the secondary reflection wave came into being.Different active absorption algorithms can effectively eliminate the secondary reflection wave according to different feedback signals and control equations.Various active absorption algorithms are verified by numerical simulation,which can effectively reduce the experimental cost and can be compared with physical experiments.It has important theoretical significance and practical engineering application value.Based on the open source software OpenFOAM,this paper studies the push plate active absorption wave making.The main results are as follows.(1)The two-phase flow mesh solver in OpenFOAM is modified and the damping wave elimination module is added to realize the passive wave elimination of waves.Based on the moving grid base class in OpenFOAM,a user-defined wave making boundary is developed.The boundary can realize two-dimensional,quasi threedimensional and three-dimensional ordinary push plate wave making,and can realize two kinds of active absorption wave making in time domain and frequency domain under two-dimensional conditions.(2)In the case of wave elimination with damping layer at the tail end,the ordinary push plate wave making experiments of two-dimensional,quasi three-dimensional and three-dimensional wave conditions are carried out respectively.The results show that the damping wave elimination module performs well as a whole,which can effectively dissipate the wave energy,and the user-defined wave making boundary can also ideally meet the needs of ordinary push plate wave making.(3)The active absorption frequency domain filter is designed under twodimensional conditions.The experiments of regular wave and irregular wave in time domain and frequency domain are carried out when the tail end is a vertical wall.The results show that the stability and accuracy of the waves generated by the two active absorption methods are significantly improved compared with the ordinary push plate wave making without passive wave elimination.Finally,by comparing the two methods,it is found that the frequency domain method is better than the time domain method in dealing with the slow drift problem and the absorption effect of irregular waves.