A moving least square immersed boundary method for SPH with thin-walled rigid structures

This paper presents a novel method for smoothed particle hydrodynamics (SPH) with thin-walled rigid structures. Inspired by the direct forcing immersed boundary method, this method employs a moving least square method for the velocity interpolation instead of the linear interpolation. It reduces oscillations due to changing relative positions between fluid grids and structures. It also simplifies thin-walled rigid structure simulations by eliminating the need for multiple layers of boundary particles, and improves computational accuracy and stability in three-dimensional scenarios. Results of the impulsively started plate test demonstrate that the proposed method obtains smooth velocity and pressure, as well as a good match to the references results of the vortex wake development. Results of the flow past cylinder test show that the proposed method avoids mutual interference on both side of the boundary, while accurately calculating the forces acting on structure. By comparing to linear least square direct forcing scheme and the diffusive direction scheme, advantages of lower oscillation and higher accuracy are proven. Results of flow past a sphere further indicate the stability of the proposed method for three-dimensional simulations.