Alignment impact of three unequal-sized square cylinders on the wake flow pattern and fluid forces

A finite volume method and a full multi-grid technique are implemented to analyze the influence of alignment type of three unequal-sized square cylinders on the characteristics of wake flow pattern and fluid forces of the flow. Three-square cylinders with different dimensions C1, C2, and C3 are arranged for three main combinations, namely, in-line arrangement, side-by-side arrangement, and staggered arrangement. Analysis of flow patterns in different regimes is performed for the different arrangement type and for Reynolds number (Re) varied in range (1, 200). The second parameter is the arrangement type. The wake flow patterns including vortex shedding and the evolution of vortices, and force coefficients are predicted and analyzed for the three unequal-sized square arrangements in terms of streamlines, iso-vortices, and drag (CD) and lift (CL) coefficient evolutions for steady and unsteady regimes. Of great interest is the analysis of the combined effect of the Reynolds number and the adopted arrangements on the bifurcation emergence phenomenon and the CL and CD evolutions profiles while predicting the critical Reynolds number for each configuration. The numerical outcomes demonstrate that Re values and the different three-square cylinders arrangements have a prominent influence on the flow characteristics. The study reveals that the unsteady regime of the flow appears in the side-by-side arrangement at (Rec = 63), in the staggered arrangement (Rec = 76), and finally in the in-line arrangement for the specific value (Rec = 146). Furthermore, the effect of different arrangements on time averaged drag and lift is explored and discussed. It is found that the in-line alignment causes a strong reduction in drag values, while highest values are obtained for the side-by-side combination.