Application Of Fluent Udf Method In The Study Of Numerical Wave Tank

With the development of computer technology, the application of the numerical wave tank(NWT) which can partly substitute physical model test to investigate wave body problem has become more and more important. The emergence of CFD software FLUENT based on Navier-Stokes equations makes the realization of numerical wave tank possible.In the study of wave body problem based on numerical wave tank algorithm, the boundary element method(BEM) is an important method. It solves Laplace equation and introduces runge-kutta technology to trace free surface elevation by Mixed Eulerian-Lagrangian(MEL) algorithm at each time stepping. This method is accurate but usually can only apply to potential flow. And the coefficient matrix is dense, which is computationally expensive. Combining the wave generation process of boundary element method with the core algorithm of FLUENT based finite volume method(FVM), a new numerical wave tank that can deal with viscous and wave breaking problem can be set up by FLUENT UDF (User Define Function).In this paper, DEFINE_CG_MOTION macro of FLUENT UDF is utilized to define velocity of piston type wavemaker. The motion of wavemaker is simulated by dynamic mesh method and VOF model is adopted to trace free surface elevation. In order to realize wave elimination at the end of real physical wave tank, DEFINE_SOURCE macro is added in governing equations of FLUENT to absorb reflecting wave at the end of numerical wave tank.It is found that the result of free surface elevation by FLUENT method agrees well with BEM method and analytical solution. This implies FLUENT method can be applied to wave body problem in future.