Vortex dynamics induced by a finite wall-mounted cylinder with various corner shapes

Abstract

The flow around a finite wall-mounted cylinder with four different corner shapes (R/D=0,1/6,1/3,1/2) is numerically investigated at a Reynolds number of 1000 and a height-to-diameter ratio of 4. For the vortex dynamics, the vortex structures in the wake undergo a series of complex evolution processes, namely, shear layer separation, C vortex, Reverse C vortex, hairpin vortex, and vortex breakdown. The influence of R/D on the flow characteristics and vortex evolution has been studied. The results indicate that the mean hydrodynamic coefficients (C¯d and C¯l) and the mean reattachment distance (LP/D) decrease with the increasing R/D. Moreover, the flow separation for R/D=1/2 is delayed by 0.49D compared to that for R/D=0. The probability density function of the reverse-flow area at R/D=1/2 exhibits a symmetrical distribution, suggesting a balanced enlargement and contraction. Numerous hairpin vortices in the far wake exhibit clear periodic oscillation behavior resembling a Kármán-like pattern. Furthermore, as R/D increases, the oscillation frequency rises gradually as well as a forward shift in the high-strength vortex interaction, while the width of the near wake gradually narrows. The evolution of spanwise vorticity over time and the results of proper orthogonal decomposition modes confirm the alternating shedding and periodic oscillation pattern akin to Kármán vortex streets.