Vortex Structures and Behavior of a Flow Past Two Rotating Circular Cylinders Arranged Side-by-Side

We present a study on the vortex structures and behavior of a flow past two rotating circular cylinders arranged side-by-side at a range of absolute rotational speeds (|α|≤2) for two different gap spacings g*=1.5 and 0.7 at Reynolds numbers Re=160 and 200. The results show that the flow becomes stabilized and finally steady beyond the critical rotational speed as |α| increases, regardless of the variation in Re and g*. The value of critical rotational speed increases with increasing Re. The wake patterns change in the unsteady regimes for g*=1.5 and 0.7. With increasing |α|, the time-averaged drag coefficient ^-C_D decreases and the lift coefficient ^-C_L increases, respectively. C_D at Re=160 and g*=0.7 decreases rapidly, resulting in the smallest value at the same |α| for 1≤|α|≤2. ^-C_D augments with increasing g* at the same |α|. For g*=1.5, ^-C_D has a little disparity between the cases of Re=160 and 200. For the flow past two still cylinders, ^-C_L is inversely proportional to g* of two cylinders for a fixed |α|, and is not dependent on Re.