A coupled finite volume-smoothed particle hydrodynamics approach to simulate the flow around a vertical free-surface-piercing cylinder

This work presents a coupled Finite Volume-Smoothed Particle Hydrodynamics (FV-SPH) approach for simulating free-surface flows around a vertical surface-piercing cylinder. The proposed method combines the strengths of the Eulerian and Lagrangian frameworks, as the Finite Volume (FV) solver effectively resolves viscous effects and boundary-layer dynamics. In contrast, the Smoothed Particle Hydrodynamics (SPH) method accurately captures large free-surface deformations and breaking. We achieve coupling via an overlapping domain decomposition with smooth blending across FV-SPH interfaces, enabling inclusion of FV forcing within the SPH regions. We introduce a new algorithm for consistent free-surface transfer and adaptive particle injection at open boundaries. The method is validated against experimental data from a fixed, bottom-mounted free-surface-piercing cylinder in an incoming stream, for Froude numbers of 0.6 and 0.73. Results show good agreement across wake features, free-surface elevation, and depth-averaged velocity fields, confirming that the FV-SPH coupling provides a robust and efficient framework for free-surface problems with strong interactions between viscous and interface phenomena.