Byung-Hyuk Lee

Mitigation Effects of Incident Bore Impact Loads Acting on a Tall Structure by Installation of Obstacles

The incident bore impact loads acting on a tall structure is simulated using the refined Moving Particle Simulation (MPS) method. The particle method is more feasible and effective than convent ional grid-based methods for the violent free-surface problems. In the present study, the simulation results for the temporal change of the hydrodynamic force on the structure and longitudinal velocity component around the structure are compared with the experiments (Radd and Bidoae, 2005). And the mitigation effects by installation of various obstacles in front of the main structure are investigated and discussed form the simulation results.

Numerical prediction for the performance of a floating-type breakwater by using a two-dimensional particle method †

Abstract The nonlinear free-surface motions interacting with a floating body were investigated using the Moving Particle Semi-implicit (MPS) method proposed by Koshizuka and Oka [6] for incompressible flow. In the numerical me-thod, more realistic Lagrangian moving particles were used for solving the flow field instead of the Eulerian ap-proach with a grid system. Therefore, the convection terms and time derivatives in the Navier-Stokes equation can be calculated more directly, without any numerical diffusion, instabilities, or topological failure. The MPS method was applied to a numerical simulation of predicting the efficiency of floating-type breakwater interacting with waves. Keywords: Floating-type breakwater, Wave transmission rate, Particle method, Navier-Stokes equation, Waves interacting with a floating body 1. Introduction In order to efficiently utilize the coastal area, vari-ous kinds of breakwater should be studied and devel-oped. Although fixed breakwaters have excellent per-formance onshore, they are associated with economi-cal and technical problems in their construction off-shore, as well as environmental by restricting the cir-culation of seawater. However, floating-type breakwa-ters have many advantages compared to fixed ones, i.e. flexibility of future extensions, mobility, preservation of environments and economical efficiency, etc. As a result, a few investigations have proposed to improve the performance of floating breakwaters [1, 2, 3, 5, 8, 11, 12, 14]. Of these, most numerical approaches relat-ing to floating breakwaters have focused on develop-ing numerical techniques that capture the fully nonli-near free-surface motion based on a grid system. However, there are many different approaches that do not employ a grid system; for example, the so-called particle methods with a fully Lagrangian treatment [6, 10]. The particle methods seem to be more feasible and effective than conventional grid methods for solv-ing the flow fields associated with complicated boun-dary shapes or coupling effects between a fluid and structure. In the present study, the efficiency of a floating-type breakwater interacting with waves was investigated numerically, using the Moving Particle Simulation (MPS) method supposed by Koshizuka and Oka [6] for an incompressible flow. In this method, more realistic Lagrangian moving particles were used for solving the flow field rather than an Eulerian approach with a grid system. Therefore, the convection terms and time derivatives in the Navier-Stokes equation can directly be calculated, without any numerical diffusion, instability or topological failure. The method consisted of particle interaction models to represent the gradient, diffusion, incompressibility and free-surface boundary conditions.