Three-dimensional Viscous Numerical Simulations of Focused Waves on Bottom-mounted Multiple Rigid Circular Cylinders

摘要

Three-dimensional viscous numerical simulations are conducted in this study concerning the focused wave acting on (1) an isolated bottom-mounted circular cylinder, (2) four identical circular cylinders in a diamond arrangement, and (3) eight cylinders arranged in a chirped array with varied spacing. The numerical model, based on a Navier-Stokes solver of Fluidity, is first validated against available experimental data of the isolated cylinder, and satisfactory agreements are obtained. This work pays attention to the near trapping of a four-cylinder cluster and the rainbow trapping of a chirped cylinder array subjected to transient-focused water waves with a broad frequency spectrum. Viscous numerical results suggest the transient-focused waves result in a rather weak near trapping in the four-cylinder cluster. However, the chirped array creates significant local amplifications through a rainbow trapping mechanism. Wave nonlinearity and viscous effects are also discussed by comparisons with linear potential flow solutions.