Minimization of undesired wave reflections at the boundaries of the computational domain in flow simulations with free surface based on the Navier-Stokes equations

准确模拟自由表面波的传播和相应的流体-结构-相互作用的能力是计算流体力学中的重要课题，特别是在海洋工业和研究方面。应用基于RANSE的模拟技术的主要困难是最大限度地减少不需要的波反射在计算域的边界，因为这样的反射可以导致相当大的不确定性的模拟结果。通过在区域边界附近的区域内的控制方程中引入源项，可以阻尼出射波。减少波浪反射的另一种方法是将RANSE求解器与第二个流求解器耦合。在这种情况下，RANSE解可以混合到其他流求解器的解中。在目前的知识状态下，选择最佳源项是一个问题，仍然没有得到充分的研究。因此，本研究项目的主要目的是开发自适应方法，以最大限度地减少不必要的波反射。在这种情况下，源项将相对于入射波进行调整，以便在模拟期间始终将其设置为最佳值。所开发的方法将最大限度地减少不必要的波反射，并在开始模拟之前预测相应的不确定性。经过充分验证的二维和三维简化的情况下，所开发的方法的适用性将被证明为典型的三维海洋流动模拟问题。

The ability to accurately simulate the propagation of free surface waves and the corresponding fluid-structure-interactions are important topics in computational fluid mechanics, especially in regards to maritime industry and research. The main difficulty in applying RANSE-based simulation techniques is minimizing undesired wave reflections at the boundaries of the computational domain, since such reflections can lead to considerable uncertainties in the simulation results. By introducing source terms into the governing equations within a zone in the vicinity of the domain boundary, outgoing waves can be damped. Another way to reduce wave reflections is to couple the RANSE solver with a second flow solver. In this case, the RANSE solution can be blended to the solution of the other flow solver. Within the current state of knowledge, selecting the optimum source terms is a problem which remains insufficiently investigated. Hence, the main aim of this research project is to develop adaptive approaches for minimizing undesired wave reflections. In this case, the source terms will be adjusted with respect to incoming waves so that they are set to their optimum values at all times during the simulation. The developed approaches will minimize undesired wave reflections and enable prediction of the corresponding uncertainties before starting the simulation. After sufficient validation for 2D and 3D simplified cases, the applicability of the developed methods will be demonstrated for typical three-dimensional maritime flow simulation problems.