ABSTRACT

Based on open source tool OpenFOAM, a self-developed solver qaleFoam is applied to generate the focusing wave and simulate the interaction between focusing wave and fixed/moving cylinder. By QaleFOAM, the focusing wave is generated by the external wave tank based on FNPT (fully nonlinear potential theory) and QALE-FEM (quasi arbitrary Lagrangian-Eulerian finite element method), and a relaxation zone is used for the wave propagation between the external wave tank and the internal NS (Navier-Stokes) domain. In this paper, the generation and propagation of focusing wave is tested first, and the wave elevation at different wave gauges is monitored to show the accuracy of focusing wave generation. Then, a cylinder fixed/moving in the incident focusing wave is simulated by qaleFoam, the wave elevation near and away from the cylinder is monitored, and the pressure distribution on the cylinder surface is probed. The computed result is compared with the experimental result to validate the numerical method.

INTRODUCTION

The focusing wave is a kind of steep wave, which usually happens in severe sea conditions and is harmful for ships and offshore structures. When some maritime accidents happen, the occurrence of focusing wave is usually monitored and observed, and the focusing wave is of large steepness and disappears soon (Nikolkina and Didenkulova, 2011). As a kind of simple shapes, the cylinder is widely applied for the design and construction of offshore structures, such as the ocean platform legs and the foundation of offshore wind turbines, and the investigation about the hydrodynamic characteristics and flow around a cylindrical structure has attracted the attention of many researchers (Mo et al., 2013; Bihs et al., 2016). For the design and hydrodynamic optimization of the offshore structures, it is necessary to take the interaction between the structure and focusing wave into account (Liu and Pino, 2004), which is related with the extreme loads of the offshore structures.

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