| Flow around an array of cylinders is often encountered in practical engineering. When flow past more than one cylinder the forces and vortex shedding pattern are very different from those of an isolated cylinder, even at the same Reynolds number.In this paper, flow around two tandem square cylinders at a Reynolds number of 100 with various spacing ratios (from 1.25 to 11.0) is investigated numerically by using a developed second-order characteristic-based split (CBS) finite element method. The study mainly focuses on the effect of spacing ratios (ratio of center-to-center distance to cylinder width) on flow characteristics to identify the critical spacing ratio. For spacing ratio 2.0≤s<4.0, a symmetric recirculation zone is observed behind the upstream cylinder, while it breaks and leads to vortex shedding in the gap at s>4.0. Additionally, for spacing ratios between 3.0 and 3.5, the steady flow is observed. The critical spacing ratio range is identified between 4.5 and 4.75 from the analysis of variation of force statistics and the Strouhal number. The results reveal that the mean and rms. force coefficients jump suddenly among the critical spacing ratio. Three interference regions, such as proximity interference region (s≤4.5), critical interference region (4.5 |
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