A Numerical Study On Dual Pontoon Floating Breakwaters Based On SPH Method

Floating breakwaters (FBWs) have many advantages, such as strong foundation adaptability, ease of water exchange, simple construction and low cost, so they have broad application prospects in these areas which include yacht marinas, artificial beach, cage aquaculture, construction site and oil platforms. Relative width, structure and mooring conditions of the pontoon are important factors that affect the hydrodynamic characteristics of FBWs. In this paper, the current relatively new SPH method is used to simulate the dual pontoon FBWs with anchor chains.In this paper, a numerical model is built to simulate the dual pontoon FBWs with anchor chains in the two-dimensional numerical wave flume based on SPH method. In this model, fluid dynamics equations are the mass conservation equation and momentum conservation equations. CSPM-R method is used in the process of these two equations converted into SPH form. Kinetic equations of the pontoon are Newton’s second law and rigid body motion differential equations. Lumped-mass method is used to simplify the chains to calculate anchor force, and iterative calculation equation of anchor force is established according to Hooke’s law and the hydrostatic equilibrium equation. Solid boundary conditions are treated by stationary particles method, and time integration is treated by the predictor-corrector format. Hydrodynamic of the single pontoon and dual pontoon FBWs is calculated by the numerical model, and numerical and experimental results are in good agreement by comparison. Hydrodynamic of single pontoon FBWs and is compared by that of dual pontoon FBWs with the same relative width according to the numerical model. Hydrodynamic of dual pontoon FBWs is calculated on the condition of different mooring configurations, different relative mopping chain lengths and different chain stiffness.The results show:although they have the same relative width, dual pontoon FBWs are more efficient than single pontoon FBWs in the aspects of wave dissipation performance, motion response and anchor force. When dual pontoon FBWs by parallel mooring are compared with dual pontoon FBWs by crossed mooring, both of them have similar wave dissipation performance, but the former is more efficient in the aspects of motion response and anchor force. Different relative mopping chain lengths and different chain stiffness have a great influence on hydrodynamic of dual pontoon FBWs by crossed mooring. The smaller relative mopping chain length and the bigger chain stiffness enables FBWs get the better wave dissipation effect, but their anchor force increases at the same time. Research work in this paper can provide a reference for engineering practice, and lay the foundation for numerical study of FBWs by SPH method.