Investigation on the flow-induced vibration of tandem cylinders with varying diameters at subcritical Reynolds numbers

Abstract

The flow interference among multiple cylinders is highly complex, and investigating it holds substantial engineering relevance. This paper considering three different arrangements at subcritical Reynolds numbers, a series of experiments were conducted to study the flow-induced vibrations (FIV) of rigid cylinders in tandem with variable diameters. Both cylinders are free to respond in both in-line (IL) and cross-flow (CF) directions. Utilizing a dynamic data acquisition system to obtain micro-strain time history information. The reference cylinder diameter (D) of 30 mm was employed as the standard for the spacing ratio (S/D). Both cylinders were exposed to uniform water flow at varying S/D: 3.0, 4.0, 6.0, and 8.0. A parametric investigation was conducted to analyze the effects of the relative spacing of the cylinders on the vibration response of the system. The results indicate that vibration intensity escalates as flow velocity increases. For the same cylinders, unsteady wave-induced vibrations (WIV) behind the upstream cylinder hinder the appearance of the lower branch of the amplitude response. Furthermore, the S/D substantially influences the cylinder vibration response. In the arrangement where the small cylinder is located upstream, the downstream cylinder undergoes WIV under smaller S/D, and the shielding effect is inconspicuous. In contrast, when the larger cylinder is located upstream, the shielding effect intensifies, leading to synchronous vibrations of the upstream and downstream cylinders. The S/D appears to exert minimal influence on the vibration under these conditions. In summary, the interference between cylinders in tandem configurations significantly impacts the vibration characteristics of the cylinders.