Unsteady computation of flow field and convective heat transfer over tandem cylinders at subcritical Reynolds numbers

Unsteady flow and convective heat transfer over single and two tandem cylinders at constant-heat-flux condition in subcritical range of Reynolds number was numerically investigated. Two-dimensional computations were performed by adopting 3-equation k-kl-ω turbulence model using a commercial software FLUENT®. The aim was to investigate the capabilities of k-kl-ω turbulence model for collective flow and heat transport conditions past cylindrical bodies and then to identify a critical spacing ratio for the maximum heat transport. The center-to-center spacing ratio (L/D) was varied in the range from 1.2 to 4.0. Instantaneous path lines and vorticity contours were generated to interpret the interaction of shear layer and vortices from upstream cylinder with the downstream cylinder. Comparison of pressure coefficients, fluctuating and average lift as well as drag coefficients, Strouhal number and the local and average Nusselt numbers with the available literatures indicated a reasonably good agreement. The combined outcome of flow field and heat transfer study revealed a critical spacing ratio of L/D = 2.2. Based on the present investigation, a correlation has been suggested to calculate overall average Nusselt number of the two cylinders placed in tandem.