The formation mechanism of recirculating wake for steady flow through and around arrays of cylinders

Abstract

The mechanism of recirculating wake formation was examined based on a series of numerical experiments on steady flow through and around periodic square arrays of evenly spaced circular cylinders. The Reynolds number of the array Re ranged from 1 to 50, and the solid fraction of the array φ was varied from 9.69 × 10-11 to 0.785. The recirculating wake was found to be completely detached from the array under a certain range of φ and Re, and varied in size with φ and Re. The trailing edge bleeding from the array affects the vortex formation in a way consistent with the entrainment-detrainment mechanism. The combination effect of vorticity accumulation and decay also gives rise to the dissipative vortex. By examining the shear layer formed by the bleeding flow and outer flow, which varies with Re and φ, it is concluded that the recirculation mainly results from flow separation at the junction point between the shear layer and the extended centerline of the array due to an adverse pressure gradient.