A unified updated Lagrangian smoothed particle hydrodynamics for fluid-structure interaction problems with moving boundaries and interfaces

Fluid-structure interaction (FSI), as a two-phase flow problem, is widely encountered in engineering, which often involves large deformation and moving boundaries and interfaces. The finite particle method (FPM) originated from smoothed particle hydrodynamics (SPH) is one of the most common meshfree particle methods, and is more accurate than conventional SPH. In this paper, based on the virtual work principle, a unified updated Lagrangian FPM framework is proposed by which both fluid and solid are discretized simultaneously. A gradient-free form of artificial pressure dissipation is used in fluid models for pressure oscillation problems. An additional artificial stiffness is introduced to control the numerical instability due to rank-deficiency in solid models. Considering FSI problem, the solid particles regarded as dummy particles are introduced into the governing equations of fluid. This technique can avoid arrangement and updating of dummy particles, and allows a convenient handling of the FSI problems with a complex moving interface. The interface force is formed by a force-pair to ensure momentum conservation. Finally, four FSI numerical tests from different degrees of tracking interface are performed to demonstrate that the method in this work can effectively handle the FSI problem with complex geometrical and moving interfaces. In particular, it is effective in the FSI cases with low and medium Reynolds number.