  This paper presents a novel method for smoothed particle hydrodynamics (SPH)
with thin-walled structures. Inspired by the direct forcing immersed boundary
method, this method employs a moving least square method to guarantee the
smoothness of velocity near the structure surface. It simplifies thin-walled
structure simulations by eliminating the need for multiple layers of boundary
particles, and improves computational accuracy and stability in
three-dimensional scenarios. Supportive three-dimensional numerical results are
provided, including the impulsively started plate and the flow past a cylinder.
Results of the impulsively started test demonstrate that the proposed method
obtains smooth velocity and pressure in the, as well as a good match to the
references results of the vortex wake development. In addition, results of the
flow past cylinder test show that the proposed method avoids mutual
interference on both side of the boundary, remains stable for three-dimensional
simulations while accurately calculating the forces acting on structure.
