Dynamic load characteristics and wake vortex structure of spiral finned cylinders in cross-flow

In this study, four types of spiral fins with varying parameters were mounted on an upstream cylinder, and the effects of spiral fins on the vibration response of heat exchange tubes and the vortex structure in cross flow were studied through experiments and numerical simulations. The results indicate a strong dependency of the cylinder's vibration response on the fin parameters. The results indicate that the vibration response and wake structure of the cylinder are significantly influenced by the parameters of the fins. The introduction of a finned cylinder affects both its own vibration amplitude and frequency, as well as the downstream cylinder. The amplitudes of finned cylinders I and III are reduced by 57.8% and 59.9%, respectively, compared to the bare cylinder. This reduction helps to restrain vibration and diminishes the amplitudes of the downstream cylinder. Although finned cylinder II slightly decreases its own vibration, it increases the amplitude of the downstream cylinder by 13.7%. The mean drag coefficient and the root mean square of the lift coefficient of the finned cylinder are higher than those of the bare cylinder when the finned cylinder is positioned upstream. Smaller pitch and larger equivalent diameter will lead to increased drag, resulting in enhanced vortex shedding in the wake, which amplifies the vibrations of the cylinder in that wake. The downstream of finned cylinder II has the widest wake and higher vortex strength, and the dynamic load and vibration of the downstream cylinder are increased. The vortex intensity decays faster in the wake of finned cylinder III, and the vibration of the downstream cylinder is weaker.