A resolved CFD-DEM-IBM algorithm for water entry problems

Abstract

A resolved CFD-DEM-IBM algorithm is proposed for elaborate numerical description of water entry process. Discretized on fixed Cartesian grids, the Navier-Stokes equations are adopted to describe the complex fluid behaviors. The motion of solid bodies and their interactions are modeled by the discrete element method (DEM). The immersed boundary method (IBM) is applied to track solid boundaries undergoing drastic movement by a series of Lagrangian points, on which the fluid-solid interaction forces are derived according to velocity boundary conditions. The free surface is captured using the improved conservation level set method which exhibits remarkable accuracy and mass conservation property. The partitioned scheme where several iterations are required is employed to realize tightly coupled fluid-solid system. Shown to be fully resolved where detailed resolution of fluid phase could be captured, the proposed method allows interaction among heterogeneous fields to be modeled with convincing accuracy. Several cases are performed to demonstrate the reliability of the algorithm whose results are in good accordance with the established data. Once validated, the proposed approach is applied to mimic water entry of multiple bodies, and particles settling in stratified fluid is conducted afterwards to reveal the versatility of the CFD-DEM-IBM algorithm for more general problems.