An investigation of the dynamic behaviour of two rigid cylinders in a tandem arrangement under vortex-induced vibration

The flow interference of multiple cylinders subjected to vortex-induced vibration (VIV) is a complex response that is not fully understood. This paper investigates the fluid-dynamic behaviour of elastically mounted rigid cylinders where both cylinders were free to oscillate in the cross-flow direction. The cylinders were subjected to uniform water flow at various separation distances of 3.5, 4.0, and 4.5D (D is the diameter of the cylinder) in a tandem arrangement. Based on the observation, the interference between the cylinders and the unsteady wake from the leading cylinder caused a continuous vibration with no lower branch in amplitude response. While as found in the cases of the single cylinder, there was a lower branch in amplitude response. The results also revealed that the cylinders experienced the VIV and wake-induced vibration (WIV) at each separation distance. Moreover, the leading cylinder oscillated at a larger amplitude at a separation distance of 3.5D, indicating a critical distance for cylinders in the tandem arrangement due to the existence of a bistable regime. Hence, it is reasonable to conclude that the flow interference between the leading and trailing cylinders significantly impacts the cylinders’ dynamic behaviour.