Numerical Study On The Flow Characteristics Around A Row Of Vertical Slotted Piles Under Solitary Wave

The utilization of pile-type structures is more and more popular in offshore engineering. However, study on the hydraulic characters around structures is rare nowadays, and mainly by physical experimental methods without complete hydraulic information. The open-source software package OpenFOAM was utilized as the tool for numerical study in this paper. Based on the incompressible Navier-Stokes equations, combined improved volume of fluid method (VOF) for tracking the free surfaces and the Spalart-Allmaras delayed detached eddy simulation (DDES) model for turbulence closure, three dimensions hydrodynamic numerical model for the simulation of solitary wave and slotted piles was built. Meanwhile, the physical experiment was conducted for the acquisition of accurate and whole hydrodynamic information around slotted piles. Through the experimental data, numerical model was validated with a good performance. Finally, a set of numerical experiments was carried out, which contained the comparison of slotted piles with single pile, slotted piles with different gap radios under non-breaking solitary wave, and another of slotted piles at different position under breaking solitary wave in swash zone. The hydrodynamic characters, such as free surface, flow structure, hydrodynamic pressure and wave force, were analyzed, with a mechanism discussion of wave energy dissipation and force characters around slotted piles. Via this paper work, the theoretical reference value is hopefully provided for the practical application of slotted piles structures in offshore engineering.Through the comparison between physical and numerical results, numerical model was available to reproduce the hydrodynamic process around slotted piles under solitary wave, with a perfect performance of seizure for 3D free surface, high-velocity flow separation in the gap and the large scale trailing vortex. The more complicated hydrodynamic change was found around slotted piles rather than single pile, which was manifested with an obvious 3D free surface character, a stronger flow separation on the cylinder surface close to the gap and a bigger trailing vortex and turbulence intensity. Gap radio directly affected the flow velocity of gap fluids, result in the huge difference of turbulence character leeward of slotted piles. Energy dissipation reflected on the free surface, namely different wave-dissipating performance. Distinct difference in the hydrodynamic complexity and energy dissipation mechanism was discovered in the process of slotted piles under non-breaking solitary wave and breaking solitary wave in swash zone. The hydrodynamic performance coupled the effect of resistivity water by piles and wave variation in shallow water, with a significant change by bore.