Simulation of flow around a row of square cylinders

Abstract

In this paper, the low-Reynolds number (Re = 80) flow around a row of nine square cylinders placed normal to the oncoming flow is investigated using the lattice-Boltzmann method. The effects of the cylinder spacing on the flow are studied for spacing to diameter ratios of 0.3 to 12. No significant interaction between the wakes is observed with spacings greater than six times the diameter. At smaller spacings, the flow regimes as revealed by vorticity field and drag coefficient signal are: synchronized, quasi-periodic and chaotic. These regimes are shown to result from the interaction between primary (vortex shedding) and secondary (cylinder interaction) frequencies; the strength of the latter frequency in turn depends on the cylinder spacing. The secondary frequency is also related to transition between narrow and wide wakes behind a cylinder.The mean drag coefficient and Strouhal number are found to increase rapidly with a decrease in spacing; correlations of these parameters with spacing are proposed. The Strouhal number based on gap velocity becomes approximately constant for a large range of spacings, highlighting the significance of gap velocity for this class of flows. It is also possible to analyse the vortex pattern in the synchronized and quasi-periodic regimes with the help of vorticity dynamics. These results, most of which have been obtained for the first time, are of fundamental significance.

2D PIV measurements in the near field of grid turbulence using stitched fields from multiple cameras

“…The behaviour of the normal CF g at x/M = 1, shown in Fig. 20, is compatible with wake interactions between closely located bluff bodies exhibiting similar in-phase and anti-phase locking, which have been previously reported in the 2D computational studies of Huang et al (2006), Kumar et al (2008). It is likely that these complex interactions are occurring between vortex streets of both horizontal and vertical rods.…”

A computational study of flow past three unequal sized square cylinders at different positions

“…Then for the fifth and the sixth configurations the primary vortex shedding frequency plays a dominant role whereas the secondary cylinder interaction frequency almost vanishes. The major role of secondary cylinder interaction frequencies was also observed by Kumar et al 31 for the flow past row of side-by-side square cylinders. Some small oscillations due to the harmonic of the vortex shedding frequency (Fig.…”

“…Based on computational resources and to avoid long running simulations, we adopt a resolution of 24-points. Kumar et al 31 report that 16-20 points cylinder resolution is sufficient.…”

From steady to unsteady laminar flow in model porous structures: an investigation of the first Hopf bifurcation

“…In that case, experimental studies [36] and later, numerical simulations 55 [37,38] have been carried out that shed light on the physics of this type of flow. A short analysis of the critical Reynolds number at which unsteadiness appears for a periodic regular array of parallel cylinders of circular cross section was reported based on numerical simulations carried out over a narrow range of the fluid volume fraction (i.e.…”