Flow-induced vibration and heat transfer in a cluster of three staggered cylinders with different angles of incidence

A two-dimensional numerical study is performed to explore the synergistic effects of the angle of incidence, gap ratio, and reduced velocity on the flow-induced vibration (FIV) and heat transfer characteristics in a cluster of three staggered, unequal-diameter cylinders. Three distinct angles of incidence (theta = 0 degrees, 15 degrees, 30 degrees) and three gap ratios (G* = 2, 4, 6) are meticulously examined to observe the effect of wake interference on the oscillation amplitude and heat transfer of downstream cylinders by considering forced convection. The investigation encompassed a Reynolds number (Re) of 100, a Prandtl number (Pr) of 0.7, reduced velocity (Ur) ranges from 2 to 20, and a fixed mass ratio (m*) of 2. A user-defined function (UDF) is employed in the Fluent solver to model the cylinder vibration. The findings revealed a captivating pattern: as the gap between the cylinders increased, the oscillation amplitude of the downstream cylinders significantly diminished while simultaneously witnessing a surge in the Nusselt number (Nu). Similarly, a remarkable escalation in both amplitude and Nu is observed when the angle of incidence is increased from theta = 0 degrees to theta = 15 degrees across all the gap ratios. However, for G* = 6 and theta = 30 degrees a reverse trend emerged, characterized by a notable decline in oscillation amplitude up to 32.25% and an exponential rise in the Nu up to 53.74%. Intriguingly, it is further discerned that augmenting theta and G* exerted no discernible influence on the oscillation amplitude and Nu of the downstream cylinder, as it functioned autonomously as a single isolated cylinder.