Flow-induced vibration of a cantilevered cylinder in the wake of another

This work presents an experimental study of the flow-induced vibration of a cantilevered circular cylinder in the wake of another cylinder, fix-supported at both ends. The diameter and spacing ratios, d/D and L/d are 0.24 – 1.0 and 1.0 – 5.5, respectively, where d and D are the diameters of the upstream and downstream cylinders, respectively, and L is the separation from the upstream cylinder center to the front stagnation point of the downstream cylinder. Measurements are performed over the reduced velocity U_r=3.8 – 68.3 (based on D and freestream velocity), with the downstream cylinder vibration, vortex shedding frequency, surface pressure distribution and flow structures simultaneously captured. The downstream cylinder accompanied by a smaller d/D and/or L/d is more susceptible to galloping vibration and hysteresis in the galloping response. The mechanism behind initiation and sustenance of galloping is unveiled. It has been found that the effective mass and damping play a key role in initiating and sustaining the vibrations. The variation in the flow structure is discussed in detail in both streamwise and spanwise directions, along with the fluid–structure interactions.