On the overset grids in computational Marine Hydrodynamics

An overview of using overset grids in computational marine hydrodynamics is presented. The main advantage of this method is the ability to capture large rigid body displacements that a ship withstands during voyage. Two different cases are presented in which overset grids are appropriate, using open source CFD toolkit OpenFOAM® [1]. First example includes wave response of a container ship scale model in regular steep waves. Results agree well with the experiment [2] which confirms the superiority of fully viscous CFD solvers for seakeeping problems. Second case is intrinsically different: open water propeller characteristics are calculated where rotating motion and advance speed are apriori known. Thrust and moment values are derived from the numerical simulation, showing good agreement with KT and KQ coefficients obtained by experiment [2]. Without any constraints in terms of motions, overset technique offers a powerful tool in numerical marine hydrodynamics despite having higher computational costs. Given the presented possibilities of overset, further work is revealed. With the possibility to validate the numerics with data from onboard measurements of a real going ship [4], expected investigations in terms of speed loss, propulsion efficiency etc. using high fidelity CFD tools are discussed.