Numerical simulation of waves and local scour around vertical cylinders in a triangular arrangement using REEF3D

Abstract

Coastal and offshore structures are generally supported by a group of cylinders. The stability of the structures can be threatened by sediment transport around the foundations. To explore this topic in detail, numerical investigations of local scour are carried out for vertical cylinders in a triangular arrangement with different gap ratios using cnoidal wave in the numerical wave tank in the open-source CFD code REEF3D. The sediment transport is solved with bed-load and suspended load formulas. The movable bed is represented with a level set function. The temporal variations of the local scour, the water particle velocity at free surface and the 3D scour contours in the vicinity of the cylinders are investigated. The numerical results are compared with experimental data and agree well. It is concluded, that scour is drastically increased with smaller gap ratios between the cylinders. In addition, existence of combined higher edge velocity and jet effects are also discussed in detail.