FSI Away Day 2011

1. Fluid Structure Interactions Research Group Numerical Investigations on Fluid-Structure Interactions Using Particle Based Methods for Marine Applications Fanfan Sun – ffs1g09@soton.ac.uk Supervisors –Dr. Mingyi Tan and Professor Jing Tang Xing Faculty of Engineering and the Environment Theory Introduction & Motivation • A general function f(x) and its gradient can be approximated by SPH in the forms: and • here the smoothing function depends on the smoothing length h. • Governing equations normally include (1) continuity equation and (2) momentum equation • 1). 2). • SPH form for these equations can be easily derived • a). and b). • Many fluid-structure interaction problems often involve violent fluid motions in marine engineering field, such as slamming and green water when a ship travels in rough seas which can produce overall momentum change and deformation of the hull. It is important to understand the interaction between fluid and structure to avoid damages caused by dynamic loads on the structures. • Traditional grid-based numerical methods like FEM and FVM built on continuous assumption are not efficient for large deformation problems involving F-S separations, breaking waves, etc. Particle based methods like Smoothed Particle Hydrodynamics (SPH) are an alternative approach to simulate rough fluid motion because of their Lagrangian descriptions and meshless properties. It also has been developed to model solid motions to improve numerical efficiencies for nonlinear violent fluid-structure interactions. Boundary treatment • Using repulsive force on wall particles • Using denser wall boundary particle Objective Figure 2.Using denser particles on wall surface To apply and improve the Smoothed Particle Hydrodynamics (SPH) method to simulate violent fluid-structure interactions. Figure 1. Using repulsive force on wall particles Examples of fluid-structure interaction simulations with SPH Figure 5. Analysis of pressure values on point (3.22,0.16) in the case of water impacting onto a fixed wall shown in Figure 3. Figure 3. Flow impacts onto a fixed wall boundary using ISPH Figure 4. Flow impacts onto a spring supported wall using ISPH Figure 6. Water entry of a wedge using ISPH Figure 8.Dropping velocities of wedge obtained by simulation and experiment Figure 9. Impacting force on the wedge shown in Figure 6. Figure 7. Wave pattern comparison between simulation and experiment Conclusions • Incompressible SPH method gives reliable pressure values • Instead of traditional ghost particle boundary treatment, repulsive boundary force and denser wall particles are two alternative treatments incorporated with ISPH which improve the simulation efficiency • SPH can be developed to create a powerful tool for fluid-structure interaction problems with large motions and deformations. FSI Away Day 2011