Experimental investigation of the vortex-induced vibration of a circular cylinder near a flat plate

The vortex-induced vibration (VIV) of a near-wall cylinder involves complex interactions between the cylinder wake and wall boundary layer. In this study, the VIV of a circular cylinder with a relatively low mass ratio m* = 43.6 located near a flat plate was experimentally investigated with 3360 <= Re <= 10,800, 3.0 <= U* <= 9.6, and 0 <= S* <= 2.5, where Re is the Reynolds number based on the cylinder diameter, U* is the reduced velocity, and S* is the gap ratio between the cylinder and flat plate. The cylinder vibration, vortex shedding mode, and pressure fluctuation on the flat plate for different S* and U* values were studied in detail. Based on qualitative and quantitative analyses of the near wake of the cylinder using smoke-wire flow visualisation and particle image velocimetry, a classification of vortex shedding modes according to the behaviours of the induced secondary vortex from the flat plate was proposed. The cylinder collided with the flat plate for 0.1 <= S* <= 0.5, and the effect of the flat plate was almost negligible at S* = 1.5 and completely disappeared at S* = 2.5. In addition, the vibrating cylinder significantly influenced the pressure on the flat plate, particularly in the area below it. Both ' the time-averaged and fluctuating pressure coefficients Cp and Cp presented their extrema at S* = 0.3 when the vibrating cylinder collided with the plate.