Numerical simulation of the flow around two side-by-side circular cylinders by IVCBC vortex method

A novel two dimensional pure-Lagrangian vortex method based on instantaneous vorticity conserved boundary conditions (IVCBC) has been applied to investigate the hydrodynamic coefficients and patterns flow around two circular cylinders in side-by-side arrangements with pitch ratios T/D=1.1-7 at a high Reynolds number Re=6×104. The benchmark case of viscous flow around a circular cylinder was first carried out to validate the novel vortex method. Then simulations of the flow around two side by side circular cylinders were performed. A new scheme was proposed to distinguish the wide wake (WW) and narrow wake (NW) by judging the velocity direction of a specific point in the gap flow. The hydrodynamic coefficients and Strouhal numbers were thoroughly studied as a function of the pitch ratios. A total of five kinds of flow patterns were identified. During the investigation of biased flow, an intermediate frequency between frequencies of NW and WW was found and approached to that of a single cylinder. The results show good agreement with the previously published experimental and numerical data.