A Multi-physics Peridynamics-DEM-IB-CLBM Numerical Approach For Solving Fluid-solid Interaction Problems

Fluid-structure interaction problems have always been a challenging field of hot spots in the academic research.An accurate and efficient numerical method for solving fluid-solid coupling phenomenon will provide reliable support for engineering practice.Based on the latest development of computational fluid and solid dynamics,this paper establishes a new numerical framework for FSI problems from three aspects,hydrodynamic solver,solid solver,and interface coupling algorithm.The peridynamic theory(PD)is employed to simulate the deformation and rupture of elastic solids,the lattice Boltzmann method(LBM)is used for solving flow field,the immersion boundary method(IBM)is adopted to implement moving no-slip boundaries in a flow field,and the discrete element method(DEM)is to model the movement and contact of rigid solids.In this paper,the multi-physics numerical framework PD-DEM-IB-CLBM and its application in a variety of complex and nonlinear FSI problems are studied to make full use of the peridynamic theory for solid rupture,as well as the IB-CLBM for tracking the no-slip boundary in flow field.The main achievements and innovation points of the paper are summarized as follows:(1)The multi-direct-forcing immersed boundary method(MDF-IBM)is improved with a relaxation technique to speed up the iterative convergence.The advantage of the relaxed MDF-IBM is validated in several classical problems including flow around a fixed cylinder,flow around three objects and particle moving in a linear shear flow.The research on the relaxed MDF-IBM benefits our following work on the coupling of the IB-CLBM and PD.(2)Benefiting from the Lagrangian characteristics of material points in the PD and the Lagrange points for describing the no-slip boundary in the IBM,the PD and the DEM are coupled with the IB-CLBM to establish the multi-physics numerical simulation framework,PD-DEM-IB-CLBM,which is expected to be a promising tool for solving complex FSI problems.(3)The DEM-IB-CLBM is validated to be effective for fully-resolved particles moving in a fluid.The formation process of the asymmetrical principal movement states of two particles in a narrow long channel filled with a viscous fluid is studied with the DEM-IB-CLBM,and the effectiveness of the method in solving nonlinear complex FSI problems is proved.The deposition of 540 particles in a closed cavity is presented to demonstrate the ability of the DEM-IB-CLBM for multi-particle problems.(4)The effectiveness of the PD-IB-CLBM in solving the active and passive interaction between the large deformation elastic solid and the flow field is verified.The PD-IB-CLBM method is used to simulate an elastic foil self-propelled by an undulatory spine and investigate the influence of the stiffness of the elastic foil and the length of the spine on the propulsive performance.The accuracy and numerical stability of the PD-IB-CLBM in dealing with the large deformation problem are demonstrated.(5)The PD-DEM-IB-CLBM is used to predict the material damage caused by the impacts of multiple particles,where the interaction between rigid particles and fluids,the collision between rigid particles and brittle walls,and the induced material damage are directly solved.It is shown that the PD-DEM-IB-CLBM can accurately calculate the damage caused by the impactors with different impact velocities and impact angles in a viscous fluid,as well as the formation and expansion of ruptures and cracks during particle impact.It is fully illustrated that the multi-physics framework PD-DEM-IB-CLBM can directly predict the erosive impact of solid particles in a fluid.The paper provides a new numerical tool for the in-depth study of related problems.