Unveiling the dynamics of 2-DOF flow-induced vibrations and heat transfer: A comprehensive study of multi-cylinder configurations

Flow-induced vibration (FIV) is a significant concern in various engineering applications, including offshore platforms, heat exchangers, and piping systems. This study investigates the impact of different configurations of two identical circular cylinders on their FIV and heat transfer behavior. By exploring tandem (α = 0°), staggered (α = 15° – 60°), and side-by-side (α = 90°) arrangements, the study examines the effects of different cylinder configurations. Allowing two degrees of freedom (2-DOF) oscillations in streamwise and transverse directions, the study provides a comprehensive analysis of dynamic responses and heat transfer characteristics across a range of reduced velocities (Ur = 0–14). The tandem configuration exhibited negligible vibrations up to Ur = 6, with significant increases observed at Ur = 8 due to lock-in phenomena. The strongest interaction between the cylinders was observed at a stagger angle of 15°, resulting in the highest vibration amplitude for the upstream cylinder. Vortex shedding patterns varied with cylinder configurations, where the tandem arrangement showed steady flow up to Ur = 6, transitioning to a strong 2S vortex shedding pattern at Ur = 8. Staggered configurations demonstrated complex vorticity patterns, with enhanced shear layer interactions leading to significant wake-induced vibrations, particularly at Ur = 6 and 8. Heat transfer analysis indicated that the average Nusselt number (avg Nu) increased with the cylinder vibrations, due to enhanced mixing of the flow. Peaks in avg Nu occurred around Ur = 6, with the highest rates observed at a stagger angle of 60°. For the downstream cylinder, the staggered configuration at α = 60° led to a 45.9 % reduction in the maximum transverse vibration and a 16.5 % increase in the maximum avg Nu compared to the tandem arrangement. In this work, reduced FIV and enhanced heat transfer is achieved, which is a desirable characteristic for heat exchangers. These results highlight the importance of cylinder arrangement in optimizing thermal performance.