Vortex shedding characteristics in the wake of circular finned cylinders

Abstract

The near wake flow development and vortex shedding characteristics downstream of straight circular finned cylinders are experimentally investigated. Different finned cylinders with the same fin pitch and fin thickness, but different diameter ratios, Df/Dr = 1.5, 2.0, 2.5, are investigated. Particle image velocimetry measurements are carried out at a Reynolds number of Re = 2.0 × 104 based on the cylinder effective diameter (Deff), which corresponds to the sub-critical flow regime. The spatial flow development in the near wake is elucidated using both time-averaged and phase-resolved flow field characteristics. The proper orthogonal decomposition analysis is used to characterize the unsteady vortex shedding process in the wake of the cylinders. The results show that adding fins to the cylinder changes the flow development around it. Moreover, the extent of the recirculation region reduces significantly downstream of the finned cylinders as their diameter ratio increases due to higher flow entrainment between the fins. This causes an increase in both the energy of the primary vortex shedding and the strength of the vortices in the wake. The combination of stronger vortices with amplified periodicity leads to a more energetic vortex shedding process in the wake of the finned cylinders.