Application of SPH Method in Large Eddy Simulation of High-speed Free Surface Flow

The basic method of smoothed particle hydrodynamics (SPH) has been applied to simulate high-speed free-surface flows such as skimming flows over steep slopes and ski jump flows involving entrainment of air bubbles and splashing of water droplets with vigourous air-water interactions. Both single-phase approach for water flow and two-phase procedure for both the air and water have been implemented. The sub-particle eddy viscosity and the wall model were used in the framework of the particle method in order to reflect the unresolvable small-scale turbulent motion and the near wall turbulence characteristics. The single-phase method has been initially tested in the calculation of dam-break flow comparing with the results obtained by using the open-source code, DualSPHysics. The present method is shown to be as good as or better than DualSPhysics. The method is then appplied to simulate high-speed free surface flows.

Two high-speed flow cases, i.e. skimming flow past a stepped channel and ski-jump flow past a flip bucket on the spillway, were simulated. These flows involve fast-moving free surface which is difficult to be simulated using the conventional grid methods. However, this kind of simulation is made possible by using the particle-based method like SPH. The boundary condition and the effects of turbulent fluctuations should be treated properly for successful simulation of such flows. The air bubble concentration profiles as well as the velocity and turbulence stress profiles are predicted correctly in the skimming flow in the stepped channel. The trajectory and the spread of the jet of the ski-jump flow are reproduced well in the spillway ski-jump flow. In the paper the numerical details are described and the calculation results are examined in detail comparing with the corresponding experimental results.