2013 Volume 1 Issue 1 Pages 44-55
A coupled fluid-structure-sediment interaction model is applied to a tsunami/storm-surge disaster mitigation structure attached with a movable crown to investigate the mechanisms of the movable crown behavior and wave energy dissipation. The model is composed of a large-eddy simulation solver for computing incompressible viscous air-water flow that considers the motion of a movable structure and the profile evolution of the seabed, a volume-of-fluid module for tracking air-water interface motion, an immersed-boundary module for computing movable structure motion, and a sediment transport module for computing suspended sediment motion and seabed profile evolution. The modules are connected to the solver using a two-way coupling procedure to ensure fluid-structure-sediment interaction. Numerical results show that the relation between the fluid inflow/outflow rate through a gap in the crown and the angle of the movable crown is an important parameter in predicting the wave field around the structure and the behavior of the movable crown. This suggests that it is essential to calibrate the parameter against the experimental data in numerically evaluating the performance of the structure for optimal design. It is also found that the motion of the movable crown is affected by the air trapped in the flood-control basin at the time of uprush and the air flow entering the flood-control basin at the time of backwash, suggesting that it is important to consider not only water flow but also air flow in the numerical simulation. Furthermore, the structure is found to efficiently dissipate wave energy due to vortices forming around the crown and the motion of the movable crown.