Flow around six in-line square cylinders

Abstract

The flow around six in-line square cylinders has been studied numerically and experimentally for 0.5 s/d 10.0 and 80 Re 320, where s is the surface-tosurface distance between two cylinders, d is the size of the cylinder and Re is the Reynolds number. The effect of spacing on the flow regimes is initially studied numerically at Re = 100 for which a synchronous flow regime is observed for 0.5 s/d 1.1, while quasi-periodic-I, quasi-periodic-II and chaotic regimes occur between 1.2 s/d 1.3, 1.4 s/d 5.0 and 6.0 s/d 10.0, respectively. These regimes have been confirmed via particle-image-velocimetry-based experiments. A flow regime map is proposed as a function of spacing and Reynolds number. The flow is predominantly quasi-periodic-II or chaotic at higher Reynolds numbers. The quasi-periodic and chaotic nature of the flow is due to the wake interference effect of the upstream cylinders which becomes more severe at higher Reynolds numbers. The appearance of flow regimes is opposite to that for a row of cylinders. The Strouhal number for vortex shedding is the same for all the cylinders, especially for synchronous and quasi-periodic-I flow regimes. The mean drag (C Dmean ) experienced by the cylinders is less than that for an isolated cylinder, irrespective of the spacing. The first cylinder is relatively insensitive to the presence of downstream cylinders and the C Dmean is almost constant at 1.2. The C Dmean for the second and third cylinders may be negative, with the value of C Dmean increasing monotonically with spacing. The changes in root mean square lift coefficient are consistent with changes in C Dmean . Interestingly, the instantaneous lift force can be larger than the instantaneous drag force on the cylinders. These results should help improve understanding of flow around multiple bluff bodies.

Numerical investigation of fluid-solid interaction for flow around three square cylinders

“…37 Chaotic flow indicates that g = 3 is critical spacing value. At g = 5, the flow finds enough space within the gaps for complete development and roll ups to form vortices (Fig.…”

Dynamic behavior of flow around rows of square cylinders kept in staggered arrangement

“…Sewatkar et al (2009) studied the combined effect of cylinder spacing and Reynolds number on the flow across a row of nine square cylinders for 30 r Re r140 and 1 r S=d r4. Subsequently, Sewatkar et al (2012) studied numerically and experimentally the flow behavior around six in-line square cylinders for 0:5 rS=d r 10 and 80 r Re r 320. Apart from confirming the various flow regimes obtained by Kumar et al (2008), they also computed the critical Reynolds numbers at which the transition from steady to unsteady flow took place for each S=d ratio through a bifurcation diagram.…”

Flow Patterns and Heat Transfer Around Six in-Line Circular Cylinders at Low Reynolds Number

“…More insight is provided by Liang et al 2009, Sewatkar et al 2012and Bao et al 2012 that studied the flow characteristics of six in-line circular or square cylinders at low Reynolds number. They focused on the near wake flow structures omitting the analysis of the far wake structures.…”