Steady separated flow around a pair of identical square cylinders in tandem array at low Reynolds numbers.

*(English)*Zbl 07124557Summary: The steady separated flow past two identical square cylinders in tandem arrangement is studied numerically. For a Reynolds number of 40, flow features are investigated for varied centre-to-centre distance, \(S\) between cylinders. The range of normalized spacing, \(\frac{S}{D}\) is 2–30 where \(D\) denotes edge length of cylinders. Based on separation topology, four distinct flow regimes are identified. In regime I, the cylinders are closely spaced and gap between the cylinders is occupied by a pair of eddies and no wake forms behind the upstream cylinder. In regimes I and II, the cylinders are bridged by zero streamlines enveloping the gap flow. Thus, the cylinders along with the enclosed fluid, act as a single obstacle. Regime II forms as a manifestation of the first bifurcation of flow; the twin eddies in the gap split into four vortices. In regime III, the second bifurcation of flow occurs. The gap recirculation with four eddies splits; the first pair of counterrotating eddies contribute to wake of the upstream cylinder whereas the other pair adheres as a tiny vortical structure to the front part of downstream cylinder. In regime IV, separation topology is characterized by individual cylinder wakes. Four separation topologies, one corresponding to each regime, are proposed. The maximum width of the recirculation zone/wake of the upstream cylinder always exceeds the width of its downstream counterpart signifying higher drag for the former. For most of regime I, the downstream cylinder acts as a streamlined body.

##### MSC:

76-XX | Fluid mechanics |

##### Keywords:

tandem square cylinders; stabilized finite-element; steady flow; regimes of flow; surface pressure; pressure drag
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\textit{D. Kumar} et al., Comput. Fluids 191, Article ID 104244, 16 p. (2019; Zbl 07124557)

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