One of the most complex topics in fluid mechanics is the analysis and simulation of fluid behavior, including the free surface in contact with a solid body and their interaction with each other. The smoothed particle hydrodynamics method, as a meshless and Lagrangian method, still has limitations in terms of accuracy and convergence, especially in the vicinity of boundaries. The implementation of the pressure gradient differential form along with the use of normalizing matrices for the gradient, divergence and Laplacian operators as well as the use of various criteria for detecting the free surface of the fluid and the dynamic conditions governing it, in the open source software DualSPHysics, the solutions proposed in this treatise to improve the accuracy and The order of convergence is maintaining stability. To show the validity of the activity, benchmark problems of Taylor-Green vortex and wave maker have been investigated. In the first problem, a significant improvement of the convergence order and an increase of three orders of accuracy is observed,
and in the wave maker problem, by adjusting the effective parameters, the first order convergence has been achieved.
On the other hand, in the platform of the standard software solver, the simulation of the interaction between the wave and the free-floating object has been carried out, and the vertical, horizontal and angular movement of the object is consistent with the experimental and numerical results, and further, the effect of shape parameters and damping coefficient on the interaction of the wave and the wave energy converter is
done. Then, using the improved solver, the received power of the wave submerged converter was checked with damping coefficient, time period, wave height, submersion depth and different shapes, and the maximum of this power was observed at the relative frequency between zero and one.