Effect of gap and diameter ratio on vortex-induced forces for cylinders in tandem at Re=100.

The article investigates fluctuations of the vortex-induced loads related to the effects of gap and diameter ratio on the mean drag and lift coefficients of the downstream cylinder, when two circular stationary cylinders of different diameters are arranged in a tandem configuration. The study is performed with the method of computational fluid dynamics for the low Reynolds number of 100. The benchmarking of the numerical model is followed by the parametric investigation with the variation of: a) the ratio of diameters of the upstream to downstream cylinder (d/D), in order to observe the effects associated with relative sizes of structures; b) the gap-to-diameter ratio (G/D), in order to observe the combined effects of varying these geometrical quantities. The results demonstrate a rapid change in the mean drag and lift coefficient values at the gap-to-diameter ratio between 2.0 and 3.0 at the diameter ratios of 0.7 and 1.0