Author(s): Dong Wang; Philip L.-F. Liu; Shaowu Li
Linked Author(s): Philip L-F. Liu
Keywords: ISPH; Local scour; Breaking waves; Turbulence modeling; Coastal structures
Abstract: Generation and transport of turbulence associated by wave breaking are dynamic, complex and multi-scale processes and extreme waves/currents may destroy the coast structures through continuous scour around them. A 3D incompressible Smoothed Particle Hydrodynamics (ISPH) erosion model is proposed to simulate the scouring process around coastal structures. The erosion model is based on the turbidity water particle concept and the sediment motion is initiated when the fluid bottom shear stress exceeds the critical value. To validate the developed model, a laboratory flume experiment was carried out to study the clear water scouring around a vertical cylinder under unidirectional current, in which high-speed video cameras were used for the real-time monitoring of sediment movement. Recently, the Incompressible Smoothed Particle Hydrodynamics (ISPH) method solving the 2D RANS (Reynolds Averaged Navier-Stokes) equations with the k–ɛ turbulence closure is constructed. The concept of “massless ISPH” utilizing the definition of "particle density" (number of computational particles within unit volume) is stressed. In the case of periodic wave breaking, the over-production of turbulence beneath surface waves is stressed and the modification for standard k–ɛ model proposed by Larsen and Fuhrman (2018) is adopted. The effects of initial seeding of turbulent kinetic energy and stress limiter coefficient λ2 are studied. An adaptive wall boundary condition for k–ɛ turbulence model is employed to avoid the unrealistic production of turbulence near the wall boundary. The GC_DS (Gradient Correction_Dynamically Stabilized) scheme proposed by Tsuruta et al. (2013) is adopted to reduce the numerical dissipation. The numerical results, in terms of free surface profile, mean velocity field, vorticity field, turbulent kinetic energy and turbulent shear stress, are compared with experimental data. Very reasonable agreement is observed. This research presents the first comprehensively validated ISPH model with the modified k–ɛ turbulence closure, which can be applied to transient free surface wave problems.
Year: 2023