Two-dimensional numerical simulation of water entry of a cylinder into waves using OpenFOAM

Wang, Kai, Ma, Xin, Bai, Wei ORCID: https://orcid.org/0000-0002-3537-207X, Qian, Ling ORCID: https://orcid.org/0000-0002-9716-2342, Li, Zhi and Li, Yibin (2023) Two-dimensional numerical simulation of water entry of a cylinder into waves using OpenFOAM. Ocean Engineering, 269. p. 113516. ISSN 0029-8018

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Abstract

During being hoisted into the waves, payloads are subjected to violent hydrodynamic impact, which brings a great challenge for deep-sea cranes’ control systems. A two-dimensional numerical model with a motion constraint is established using OpenFOAM software to investigate the water entry of a cylinder into waves with the cavity effect. The accuracy of the numerical model is first verified by the water entry of a cylinder into the calm water. The mesh convergence analysis indicates that the jet profile is highly dependent on the mesh close to the cylinder surface. For the simulation of hoisting the payload into waves, a constraint for the 6 DOF rigid body motion solver is introduced, which can simulate the cylinder lowering in the air with a constant velocity and then falling freely into the wave. With the proposed model in this paper, the water entry of a cylinder into waves is analyzed by dividing the entry process into four stages. Various case studies are carried out to investigate the physical effects of the entry position (crest, trough, upward point, and downward point), and the entry velocity on the hydrodynamic forces, pressure distribution, and free surface profile. Numerical results indicate that the wave particle velocity and wave slope are the essential factors for the asymmetry of pressure on the cylinder. The results also show that the cavity that forms above the cylinder top surface causes a sharp fluctuation of the hydrodynamics force on the cylinder and the cavity volume is positively related to the effective entry velocity. All of the numerical simulation results provide the fundamentals for further research and safe control of offshore lifting or lowering.