For the Navier-Stokes equations model, the internal wave maker using a mass source function has been used to generate linear and nonlinear waves. Nonetheless, almost every numerical experiment is performed in two dimensions and only a few tests have been expanded to three dimensions. More recently, a new type of an internal wave maker has been proposed using a momentum source function. The momentum source function includes a parameter for directional wave generation in a numerical wave basin. In this study, an internal wave maker using a momentum source function is employed to generate directional linear waves in three dimensions.
Since the computer technology has been dramatically improved lately, numerical modeling becomes more popular and important in a research area of water waves. The transformation of waves may be simulated by using the appropriate governing equations. The governing equations should be numerically solved in both time and space. However, some problems arise during numerical modeling of wave transformation. One of the key problems is re-reflection to the computation domain at the incident boundary. Many numerical techniques have been developed to solve the problem and the internal wave generating-absorbing boundary condition has been commonly used in conventional numerical wave models. Numerical modeling of water surface waves using the Navier-Stokes equations (NSE) has recently became increasingly popular, since these models surpass the depth-integrated equations-based wave models. Specifically, the NSE-based models can solve the complete momentum equation including the vertical components as well as the nonlinear terms and turbulent stresses. Therefore, those models are capable of considering nonlinearity, dispersion and breaking waves, which most of the conventional wave models cannot do. Although application of the model is still in an early stage, numerical studies using the NSE-based models for modeling of water waves has been increasing.
