Numerical and Experimental Damping of Piston and Sloshing Motions in Moonpools

Damping of waves in moonpools has been investigated. Several different geometries of the moonpool have been considered, which are being mainly characterised by a piston motion of the free surface in the moonpools, while some sloshing effects are visible. A numerical damping approach has been implemented into a viscous solver to simulate the effect of perforated bulkheads without the necessity to create a complex grid. The simulations have been compared with respective model tests. Two different porosities of the bulkhead have been experimentally investigated. The simulations have been conducted for a variety of Froude numbers, moonpool layouts and in calm water as well as waves. A dependency of the surface elevation natural frequency on the ship speed has been found. Furthermore, the numerically determined surface elevation inside the moonpool has been compared with respective experimental data. Based on the surface elevation, the resulting damping for the different layouts is determined and discussed.