Numerical Simulation of Strongly Coupled Liquid Fluids in Tanks inside of Floating Body and its Motions with Incoming Lateral Regular Waves

Abstract

. Numerical method to simulate the motions of the floating body coupled with the tank liquids inside of the floating body using the overset grids method is developed. An in-house structured CFD solver which is capable the moving grid technique and overset grids method is utilized. The governing equations are 3D Navier-Stokes equations for the incompressible flow. Artificial compressibility approach is used for the velocity-pressure coupling. Spatial discretization is based on a finite-volume method. An interface capturing method based on a single phase level set approach is employed to simulate the liquid surface. Lateral regular waves are generated in the regions inside of the computational domain. The motions of the floating body are introduced by solving the motion equations and the hydrodynamic forces of the tanks are treated as the external forces in the motion equations. The computational grids of the floating body and tanks deform with the motions using the moving grid technique. The weight values for the overset-grid interpolation are determined by an in-house system which is based on Ferguson spline interpolation. The present method is applied to the condition with the floating box which has the 4 tanks inside and the lateral incoming regular waves. The overset grids are composed by the grids of the floating box, 4 tanks and background rectangular grid which generates the lateral regular waves. The amplitudes of the motions of the floating box are compared with the measured data and the present results show the features changing with the wave length ratio which are strongly affected by the liquid fluids inside of the tanks. The free surfaces around the floating box and inside of the tanks are indicated, and the interactions between the floating box and the liquid fluids of the tanks are revealed.