On CFD Numerical Wave Tank Simulations: Static-Boundary Wave Absorption Enhancement Using a Geometrical Approach

TL;DR

This paper extends static-boundary wave absorption methods in CFD simulations to deeper waters, optimizing absorption performance and validating results through numerical and experimental wave-structure interaction tests.

Contribution

It introduces a geometrical approach to enhance static-boundary wave absorption in deep water, providing an optimization framework and validation for practical CFD applications.

Findings

Wave reflection reduced by about 50% in deep-water conditions.

Absorption depth correlates with incident wave conditions for optimization.

Numerical model shows acceptable agreement with experimental data.

Abstract

The present study aims to extend the applicability of the static-boundary absorption method in phase-resolving CFD simulations outside the conventional shallow-water waves limit. Even though this method was originally formulated for shallow-water waves based on the conventional piston type wavemaker, extending its use to deeper water conditions provides a more practical and computationally cost efficient solution compared to other available numerical wave absorption alternatives. For this sake, absorption of unidirectional monochromatic waves in a semi-infinite flume by means of a static wall is investigated theoretically and numerically. Moreover, implementation to a practical wave-structure interaction application is investigated numerically and experimentally. A phase-resolving numerical model based on the Reynold-averaged Navier-Stokes (RANS) equations is implemented using the open source C++ toolbox OpenFOAM. The study presents the performance of the static-boundary method, in a dimensionless manner, by limiting the depth at which the active-absorption conventional-piston velocity profile is introduced; as a function of incident wave conditions. Moreover, it is shown that the performance of the static-boundary method can be significantly enhanced where wave reflection was reduced to about half of that of the conventional setup in deep-water conditions. Furthermore, the absorption depth is correlated to the incident wave conditions; providing an optimization framework for the selection of the proper dimensions of an absorbing wall. Finally, wave-structure interaction experimental tests were conducted to validate the numerical model performance; which shows an acceptable agreement between the model and the experimental observations. The proposed limiter is straight forward to be applied in pre-existing wave-structure interaction CFD solvers, without the need of code modifications.