Flow and heat transfer characteristics during the flow around tandem of circular cylinders

The forced convection into the tandem circular cylinders is investigated using gradient heatmetry and particle image velocimetry-based experiments. The study's objective is to understand the effect of geometry on the flow characteristics and heat transfer coefficient distribution over the heat transfer surface. The experiments are conducted over Reynolds numbers $\mathrm{Re}=9600$ and $\mathrm{Re}=20200$, thereby uncovering there is highly complicated flow structure, depending on centre-to-center spacing and orientation of the two cylinders with respect to free-stream flow. Different transversal and longitudinal pitch ($S_{1}$ and $S_{2}$, respectively) between the cylinders are considered, and its effect on the flow and thermal characteristics are studied. Velocity fields and longitudinal and transversal velocity components obtained using Particle Image Velocimetry (PIV), and heat transfer parameters obtained using gradient heatmetry and temperature measurement. The distributions of the local heat transfer coefficient on the heat transfer surface are obtained. Based on these distributions, the surface-averaged Nusselt number for the studied Reynolds number is determined.