사항하는 VLCC 탱커선에 대하여 중첩격자계를 활용한 RANS 유동해석

Abstract

The turbulent free surface flow around the VLCC tanker is numerically simulated using the finite volume based multi-block RANS code, WAVIS , developed at MOERI. WAVIS uses the cell-centered finite volume method for discretization of the governing equations. Convection terms are discretized using the third order MUSCL scheme and the central difference scheme is utilized for diffusion terms. To ensure divergence-free velocity field, the SIMPLEC method is employed. The realizable k-ε turbulence model with a wall function is employed for the turbulence closure. The free-surface, the interface of two fluids, is captured with the Level-Set method in two-phase flow formulation. In order to improve the computational efficiency, the finite volume based multi-block RANS code, WAVIS, is converted into MPI- parallelized code with a LINUX PC-clustering machine. Another improvement of present numerical scheme is about the introduction of the overset grid scheme. The overset grid approach for structured grids is often used to handle a multiple-body problem with relative motion or to handle complex geometries by the structured grid method. For easier grid generation for the obliquely towed a ship, The background grid system without a hull and the grid systems for the hull with various drift angles are overlapped. The computed results are compared with the experimental data provided by CFD Tokyo workshop 2005 in terms of wake distribution and hydrodynamic forces and moments with various drift angles for the modified MOERI VLCC tanker (KVLCC2M).