Direct numerical simulations of flow and heat transfer over a circular cylinder at Re = 2000

Unsteady direct numerical simulations of the flow around a circular cylinder have been performed at Re = 2000. Both two-dimensional and three-dimensional simulations were validated with laminar cold flow simulations and experiments. Heat transfer simulations were carried out and the time-averaged local Nusselt number at the cylinder surface was obtained for various Reynolds numbers. Finally, the heat transfer of 2D and 3D simulations are compared. The average Nusselt numbers were found to be in accordance with empirical correlations. The 3D simulation gives a higher heat transfer due to the captured effects of motions in the spanwise direction compared to the 2D simulation. The irregular fluctuation of surface-averaged Nusselt number can be captured by the 3D simulation, while 2D simulation results show a regular fluctuation corresponding to the shedding from the cylinder, similar to that of a laminar flow.