Wake-induced vibration and heat transfer characteristics of three tandem semi-circular cylinders

Abstract

This paper studies the wake-induced vibration (WIV) and heat convection of the downstream tandem bluff bodies under the influence of an upstream bluff body at Re = 200 and Pr = 0.7. For the reduced fluidic velocity (Ur) in the range of 1–16 and different bluff body diameter ratios (d/D), three wake interference patterns, namely, the quasi-co-shedding (QCS) pattern, the co-shedding (CS) pattern, and the coupling between QCS and CS (QCS-CS) are formed due to the interference between the shear layer and vortex shedding process. The occurrence conditions of the three patterns are closely related to Ur and d/D. The vibration response of the midstream bluff body is roughly consistent with that of a heat-isolated semi-circular cylinder (HISC) if d/D is small. By increasing d/D, the vibration amplitude of the midstream bluff body first increases, then decreases with Ur. The vibration amplitude of the downstream bluff body starts to increase from small d/D and then can maintain a high value with the increase of Ur, even at large d/D. Compared with the HISC, the tandem configurations can help reduce the drag force. Because of the wake interference and the ‘blocking effect’ from the upstream bluff body, although the heat convection of the midstream and downstream bluff bodies can be effectively strengthened through WIV, the time-averaged Nusselt numbers (NuA) of the midstream and downstream bluff bodies are still lower than that of the HISC. Besides, heat transfer efficiency has been found to correlate with the transverse vibration amplitude of bluff bodies. Moreover, it is revealed that there is a trade-off between the heat transfer efficiency of the equipment and its service lifespan because increasing the vibration amplitude enhances convection but also increases the risk of potential damage to the structural integrity.