A MUSCL-MC-reconstructed Riemann-SPH model with a single-layer dual-sided particle boundary for fluid-solid coupling

This paper presents a Riemann-SPH framework incorporating MUSCL reconstruction with the monotonized central (MC) limiter for fluid-solid coupling, together with a novel single-layer dual-sided particle boundary model. To alleviate the excessive Riemann-solver dissipation, a limiter controlled by the pressure convection rate is introduced to adaptively regulate the numerical dissipation in impact-dominated regimes. A localized dynamic-pressure-based reconstruction (LDPR) technique is derived by excluding the hydrostatic pressure component from the pressure contribution to the continuity equation, thereby mitigating free-surface instability in long-term simulations. For complex and thin-walled structures, a single-layer dual-sided particle boundary model is developed for fluid-solid coupling simulations. It reduces boundary discretization cost and enables accurate and efficient two- and three-dimensional simulations involving complex geometries and multiphase flows. Furthermore, an enhanced particle shifting algorithm, specifically designed for single-layer boundaries, is implemented to alleviate numerical instabilities arising from irregular particle distributions. The proposed model is validated through several benchmark tests against experimental data, analytical solutions, and results from other numerical methods. The results demonstrate improved accuracy, high numerical stability, and excellent energy conservation properties of the proposed approach in SPH simulations of fluid-solid coupling.