Numerical simulations are carried out to study the flow around two tandem square cylinders (SC) under the effect of spacing ratio(g/D) and splitter plate length (l/D) for a fixed Reynolds number (Re)=100. The g/D is varied from 0 to 10 and l/D is varied from 0.5 to 10. The splitter plate length is found to have strong effect on vortex shedding and fluid forces. The maximum reduction in mean drag coefficient is observed at l/D=8, that is 15 and 78 for upstream and downstream cylinders, respectively. The maximum reduction in root-mean-square value of lift coefficient is found at l/D=10, that is 99. The flow pattern at both of these points is steady flow. There is 100 vortex shedding suppression for l/D>5. The observed flow patterns for flow past tandem cylinders without splitter plate are; single bluff body (SBB), steady flow (SF), quasi-steady flow (QSF), fully developed flow (FDF) and fully developed two-row vortex street flow (FDTRVS) regimes. SBB, QSF and SF regimes were observed in presence of splitter plate.

The transition of viscous fluid flow around the square cylinder placed in a computational domain with a sudden expansion at low Reynolds numbers (Re) is investigated numerically by using the lattice Boltzmann method. The flow analysis is based on various Reynolds numbers and expansion ratios of the channel for different gap spacing ratios (g^*), and both the Re and gap spacing ratios are studied for g^* = 1, 5, and 10 and Re = 75, 100, 125, and 150, respectively. Here, g^* = g/D, where g is the expansion ratio of the flow and D is the diameter of the cylinder. From the flow phenomena, we observed that the flow remains symmetric to a certain level depending on low Reynolds numbers. Hydrodynamic forces of the cylinder are strongly based on the expansion ratios. The effect of various Reynolds numbers and gap spacing ratios on the lift forces and drag coefficient is also analyzed. The bifurcation phenomena of asymmetric to nonasymmetric states occur with the increase in Reynolds numbers and expansion and spacing ratios.