Numerical simulation of two-phase flow in offshore environments

Numerical Simulation of Two-Phase Flow in Offshore Environments Rik Wemmenhove Weather conditions on full sea are often violent, leading to breaking waves and lots of spray and air bubbles. As high and steep waves may lead to severe damage on ships and offshore structures, there is a great need for an accurate prediction of hydrodynamic wave loading. The thesis describes a method to simulate the fluid flow for violent flow conditions. Not only the water motion, but also the dynamics of air bubbles below water and air above the free surface have been modeled. The flow of water and air is described by the Navier-Stokes equations. These equations are solved by splitting up the flow area into a large number of computational cells. Subsequently, the flow properties are determined in time for every computational cell. The flow of water and air around the free surface requires special attention, since that is the region with the most complex flow and generally the highest flow velocities. The numerical method has been validated extensively with results from model experiments. To this end, measurements have been performed on the flow after a dambreak, the sloshing motion in fuel tanks and the wave motion around a floating offshore platform. During the simulation of these experiments, modeling both water and air yields a more complete picture of the flow, while the hydrodynamic wave loading on offshore structures can be determined more accurately, especially for violent flow conditions