Abstract: When the boundary force method, virtual particle method, or coupling force method based on the traditional
smooth particle hydrodynamics (SPH) method is used to treat solids entering water, the particle density at the
fluid-solid interaction interface is discontinuous, the pressure is unstable, and some fluid particles penetrate the solid
boundary or separate at this boundary. In addition, the fluid surface will be rougher under force after the surface is
broken. Aiming at the above problems, this paper combined the advantages of the boundary force method and virtual
particle method, and improved the coupling force method to deal with the moving solid boundary to prevent fluid
particles from penetrating the solid boundary. The pressure calculation method of the interactive interface was
enhanced, the calculation accuracy was increased, and the pressure field of the interactive interface was stabilized.
Corrections were made to the particle position on the fluid surface to improve the simulation effect of the free-flowing
liquid surface boundary on the fluid surface. The proposed method was verified by the classic two-dimensional solid
entering water experiments. The experimental results show that after fluid particles interact with solid particles, stable
interface pressure can be maintained using the method in this paper, the interface separation is clear without penetration, the surface fluid particles are uniformly distributed, and the movement of the flow field is real and
natural.

Key words: smoothed particle hydrodynamics method, objects into the water, boundary pressure treatment, correction
of surface particle position