A robust Volume of Fluid (VOF) technique is presented together with an incompressible Euler/Navier Stokes solver operating on adaptive, unstructured grids to simulate the interactions of extreme waves and three-dimensional structures. The incompressible Euler/Navier Stokes equations are solved using projection schemes and a finite element method. The classic breaking dam problem is first used to validate the three-dimensional computer code developed based on the method described above. The computer code is then used to simulate the sloshing of a partially filled two-dimensional tank due to sway excitation. The resulting wave heights and pressure forces for various excitation frequencies and amplitudes are compared with experimental data and those predicted by the SPH method. The numerical simulation of the sloshing of a partially filled three-dimensional tank is carried out and compared with its counterpart of a two-dimensional tank. The computational results demonstrate that the present CFD method is capable of simulating the violent resonant free surface flows with strong nonlinear behavior in a partially filled tank, which is of great importance to the offshore and shipping industry.
In rough seas, ships or offshore structures may experience highly nonlinear phenomena such as slamming and green water on deck. Impact loads due to slamming and green water shipping are associated with the three dimensional flows with a violent free surface. A ship carrying liquid cargo in partially filled tanks in waves may experience violent sloshing even in low sea state. When the forcing frequencies are in the vicinity of the lowest natural frequency for the fluid motion inside a smooth tank, a violent free surface wave may be observed even if the tank oscilates with a small amplitude. The resulting impact loads are also due to the violent free surface motion.
