Influenced by the wake flow of upstream cylinder

the downstream cylinder is prone to wake-induced vibration at small wind angles. Although fluctuating lift is closely related to wake-induced vibration

the characteristics of fluctuating lift are less investigated

and the flow field mechanisms are not yet clear. For two staggered circular cylinders with center-to-center pitch ratio P/D of 1.5-4

by using the large eddy simulation (LES) method

the intrinsic relationships between the fluctuating lift of the cylinders and the flow fields were studied at small wind angles (β=0°-30°) with a high Reynolds number of Re=1.4×105. The interference mechanisms between the two cylinders were explored based on the flow field mechanics. Results show that the fluctuating lift of the cylinders and the flow field mechanisms experienced significant changes at small wind angles

and there were five different interference flow patterns

namely

wake interference

shear layer interference

proximity interference

interaction between vortex and cylinder

and interaction between vortex and vortex. Under wake interference and shear layer interference

the fluctuating lift of the downstream cylinder was much smaller than that of a single cylinder. Under proximity interference

the interaction between the two cylinders was weak

and the fluctuating lift of the downstream cylinder was close to that of a single cylinder. For the interaction between vortex and cylinder and the interaction between vortex and vortex

the fluctuating lift of the downstream cylinder was higher than that of a single cylinder

and the wake vortex impinging of the upstream cylinder on the downstream cylinder or the interaction with the downstream cylinder led to the rapid increase of the fluctuating lift of the downstream cylinder.