Abstract: Flow-solid boundary processing has always been the focus of fluid simulation, and
boundary force method and virtual particle methods are commonly used to study fluid-solid boundary.
The boundary force method prevents particles from penetrating by applying repulsive forces to
particles laid on the boundary, but the calculation of boundary forces limits the simulation speed. The
virtual particle method generates virtual particles at the boundary, but with the increase of the number
of particles, the number of virtual particles required increases too, resulting in a decrease in
computational speed, and the separation of fluid and boundary. For solving these problems, this paper
proposes a boundary processing method of symmetric area, which meets the real-time requirements
on the premise of ensuring fidelity, and with the increase of the number of fluid particles, the increase
of the time consumed by this method is obviously slower than that of other traditional methods, which
is more suitable for the simulation of complex scenes, while avoiding the separation of fluid and boundary at the boundary. The CSF (continue surface tension) method is a common method for
dealing with surface tension. It can calculate the surface tension as volume force, which greatly
reduces the effect of surface shape on curvature calculation, whereas in fact curvature calculation is
only related to the shape of the surface. To solve this problem, the CSF method is improved and a
surface tension calculation method based on surface particle extraction is proposed, which reduces the
error of the traditional CSF method in calculating curvature, and improves the calculation speed. The
simulation results verify the effectiveness of the proposed method.

Key words: SPH method, fluid simulation, boundary processing, symmetric region, surface tension;
CSF method, surface particle extraction