Forced convection heat transfer from an asymmetric wavy cylinder at a subcritical Reynolds number

Abstract

The present study considered the asymmetric wavy (ASW) disturbance which has been confirmed as the passive control to modify the force coefficients Yoon et al. [25]. We evaluated the effect of the asymmetric wavy disturbance on the forced convection heat transfer. For the purpose of the comparison, the smooth (CY) and symmetric wavy (SW) cylinders are considered. Finally, the LES has been carried out to solve the momentum and energy equations governing the flow and thermal fields at the subcritical Reynolds number of 3000. The validation of the present numerical methods were successively done by comparing the force coefficients and the Nusselt number with the previous results. The ASW cylinder provided the smallest mean and fluctuation of the time-and total surface-averaged Nusselt number than the CY and SW cylinders. This dependence of the Nusselt number on the cylinder shape is correlated to the force coefficients. The time-and local spanwise surface averaged Nusselt number of the SW cylinder shows the regional dependent behaviors of an invariant region and an increasing region. The ASW cylinder shows the increasing and decreasing behaviors in the short and long wavelength parts. The double wavy formation of the temperature isosurface in the wake for the ASW cylinder is consistent with the 3D vortical structures. The most significant variation of the time-averaged local Nusselt Number appears in the upstream surface of the SW and ASW cylinders which induce the spanwise dependent incoming flow.