Numerical analysis of flow interference passing through tandem cylinders at Re = 3900

This study presents a numerical model based on large eddy simulation (LES) using OpenFOAM to examine flow interference around two identical tandem cylinders at a Reynolds number of 3900, within the subcritical flow regime. The numerical method for the solution of incompressible Navier–Stokes equations is validated for the flow past single demonstrating strong agreement with the literature. The investigation focuses on separation distances (L/D = 3) to observe flow interference patterns. Flow bistability is confirmed by alternating between two distinct flow regimes. Two vortex shedding frequencies are found at St = 0.167 and 0.325 for L/D = 3 case, and these two frequencies are associated with two vortex shedding patterns in the 'reattachment' and 'overshoot' regimes, respectively. Detailed flow interference between two cylinders in the media of vortices do not synchronize with vortex shedding in the wake region, beginning with a detached shear layer rolling up to form a gap vortex and ending at the upstream cylinder return to stationary. Additionally, the phase average technique offers valuable insights into the hybrid vortex shedding pattern of bistable flow, associated with flow interference. Finally, the critical spacing for Re = 3900 is L/D = 3.7, with two vortex shedding frequencies at St = 0.155 and 0.542.