In this paper, complicated hydrodynamics of a horizontal circular cylinder entering water is investigated
numerically for low Froude numbers. A numerical approach is used to model the solid-liquid interactions in
presence of a free-surface. The governing equations for the 3D incompressible fluid flow are continuity and
Navier-Stokes equations along with an equation for the free surface advection. To track the free-surface motion,
the fast-fictitious-domain method is integrated into the volume-of-fluid (VOF) technique. The governing
equations are solved everywhere in the computational domain including the horizontal cylinder. A rigid body
motion is applied to the region occupied by the circular cylinder. The no-slip boundary condition on the solidliquid interface is exerted implicitly via increasing the viscosity of the region occupied by the solid. To validate
the numerical scheme, the results are compared with those of the experiments available in the literature. The
effects of cylinder diameter, length, impact velocity, and cylinder-water density ratio on the non-dimensional
depth are also investigated.