Investigating the effect of the flow direction on heat transfer and energy harvesting from induced vibration in a heated semi-circular cylinder

Abstract

The present study examines the flow and heat around low-mass arched forebodies (AF), flat forebodies (FF) and a circular cylinder (CC) in the presence of buoyancy. The Richardson number prescribed in this investigation varies from 0 to 1.5 for the Prandtl number of 0.71 and Reynolds numbers of 100 and 200. Selecting five semi-circular cylinders with various length-to-diameter ratios (L* = L/D) aims to investigate the influence of L* on energy harvesting. The arched and flat surfaces exposed to the incoming flow can result in experiencing heat transfer augmentation due to the separating shear layers. The functional dependence of drag coefficient, lift coefficient, non-dimensional maximum vibration amplitude, and output power are analyzed and examined in detail. The main novelty introduced in current investigation is to determine a bluff body that generates a substantial amount of vibration in order to capture maximum energy. Another connotation of this study regards the possibility of employing a numerical approach to combine the effects of geometry and buoyancy to alter heat transfer as well as extracted flow energy. Increasing the Richardson number results in increased heat transfer and energy harvesting. This is because the interaction between fluid and bluff body in the presence of buoyancy can cause disruption of the thermal boundary layer, thereby augmenting heat transfer. In the absence of buoyancy force, the circular cylinders with L* of 0.5 and 0.6 for the flat forebody configuration gain the highest extracted power at Reynolds numbers of 100 and 200, respectively, resulting in 3.5 and 5.3 times more extracted power compared to the circular cylinder. Considering extracted power, it is shown that a D-shaped configuration is less dependent on buoyancy force compared to an inverted D-Shaped configuration. The flat forebody configuration always harvests more energy than the same body with opposite flow direction. These results are capable of providing deeper insight into configuring the thermal systems, which are able to dissipate heat loads as well as produce maximum power. Having compared some of the outcomes of present work with other studies, a good agreement has been achieved to validate the simulations.