Investigation of flow and heat transfer characteristics around two tandem and side-by-side cylinders using double-distribution lattice Boltzmann method

This article describes a numerical investigation of the flow over two circular cylinders in tandem and side-by-side arrangements with different spacings at a Reynolds number of 100 using double-distribution lattice Boltzmann method. By comparing and analyzing the vorticity field, temperature field, phase diagram structure and St, the relationship between the typical flow pattern and heat transfer characteristics of the two cylinders in series and side-by-side arrangement is established. The numerical results reveal two distinct flow patterns in the tandem arrangement. In the co-shedding pattern, where the incoming flow condition of the downstream cylinder is the oscillating hot wake of the upstream cylinder. The Nusselt number of the upstream cylinder can rapidly increase to the value of a single cylinder, but the Nusselt number of the downstream cylinder can only increase to 80% of that of the upstream cylinder. Four flow patterns can be identified in the side-by-side arrangement. In the flip-flopping pattern, the interference of the gap flow with variable deflection angle on the near-wake region leads to a rapid increase of Nusselt number, but the flow and heat transfer characteristics appear to be chaotic. The appearance of the two coupled vortex streets in the two synchronized patterns further increases the Nusselt number. In addition, the variation of Nusselt number with spacing in the side-by-side arrangement is positively correlated with the vortex shedding frequency.