Study on Effects of Propulsion on Hydrodynamic Forces acting on Hull and Lower-hull of Outboard Engine by using a commercial CFD

Abstract

　The purpose of this study is to simulate the performance of real-scale high-speed planing craft with outboard engine running on the water surface as a gas-liquid surface in a two-layer fluid using the "ITO" supercomputer and reveal the effect of propulsion on hydrodynamic forces acting on hull and lower-hull of outboard engine. In the studies of prismatic planing surface, it is shown that high resolution of partial mesh around stagnation line and application of surface tension model are significant to obtain highly accurate calculation results. The same procedure is applied for a planing craft with outboard engine, and the hydrodynamic forces acting on the planing craft with outboard engine are calculated and the calculated results are compared with measured results. The calculations for the planing craft with outboard engine excluding the propeller are also performed to investigate the effects of propulsion on the hydrodynamic forces acting on the hull and lower hull of the outboard engine and on the flow field. As a result, the force parallel to the keel line increases by 10% and the force normal to the keel line decreases by 5% due to propeller action, and the lower-hull of the outboard engine is significantly affected.