Mesh Validation and Resistance Prediction of the JBC Bulker Design using CFD Method

Abstract

In the preliminary stage of ship design, resistance prediction is a primary challenge for designers. The objective of the thesis is to predict the total resistance and its components of JBC bulker with the RANS method. As a mature approach, CFD is an effective tool to estimate resistance. The well investigated hull form KVLCC2 is used to study the accuracy of the CFD calculation and to validate the resistances and the flow field around the hull by comparing it with existing experimental data. Simulations are performed using the open source software package OpenFOAM. A steady state RANS solver is used to solve the viscous flow around the hull and two-equation KOmega SST model is selected for the turbulence modeling. The vessels are implemented in a fixed towing condition where the effect of trim and sinkage is neglected. The commercial mesher HEXPRESS is used to generate unstructured hexahedral meshes of the fluid domain. Local grid refinements are carried out by setting the multi-block meshes and the free surface is captured via VOF method. Additional refinement mesh is given in the boundary areas of the hull and the wall function is implemented to simulate the turbulence characteristics. A suitable value of turbulence intensity is obtained after a set of tests in order to get the right turbulence parameters. In addition, the effect of grids with similar configuration is investigated and 5-level gradual refinement meshes are studied. The resistance components and the wave elevations in three different wave cuts are compared with the experimental results, which show a good agreement. The most proper mesh configuration with good accuracy is selected to convert to the JBC bulker. At the end, the calculated resistances and three different transverse wave cuts of the bare hull JBC bulker in calm water condition are presented.