Two-Degrees of Freedom Flow-Induced Vibrations and Heat Transfer of Twin Cylinders in Tandem and Staggered Arrangements

The emergence of flow-induced vibrations (FIV) is critical in industrial systems like heat exchanger tubes and marine risers, posing challenges in modern shell-and-tube heat exchanger design due to tube failures from fatigue damage. This work explores the impact of cylinder configurations on flow-induced oscillations and heat transfer in laminar regime at a Reynolds number of 100. Both cylinders were allowed to oscillate in two-degrees of freedom, experiencing motion both along the flow direction (streamwise) and transverse to it. The configuration of the two identical circular cylinders varied from tandem alignment (α = 0°) to staggered (α = 30° and 60°). The spacing between the two cylinders remained at 6D, with D representing the cylinder’s diameter. The cylinders were heated at a constant temperature to observe the heat transfer characteristics influenced by the two-dimensional FIV. To investigate the FIV, the reduced velocity (Ur) was systematically adjusted within the range of 2 to 12. The findings revealed the responsiveness of the cylinders to variations in reduced velocity and cylinder configurations, particularly with regard to vibrations and heat transfer. The tandem alignment resulted in most pronounced vibrational responses in both cylinders. Both cylinders exhibited lock-in behavior within the range of Ur = 6 to 8, with significant transverse vibration amplitudes. Downstream cylinder (D_C) experienced the widest span of lock-in in the tandem configuration. Streamwise vibrations were insignificant when compared to their transverse counterparts. Different vorticity patterns emerged in the wake of the cylinders, due to the different configurations. The staggered setup with α = 60° lead to a substantial 75% reduction in transverse vibrations and a 9% elevation in the Nusselt number for D_C compared to the tandem configuration.