Numerical investigations of the flow-induced vibration of a three-dimensional circular cylinder with various symmetric strips attached

Changes to the surface morphology of a cylinder immersed in a uniform flow may affect the surrounding flow characteristics. Circular cylinders with various symmetric strips attached are ideal models for studying this subject. This study investigates the flow-induced vibration (FIV) of a three-dimensional cylinder with symmetric strips attached using the delayed detached-eddy simulation method. First, the effects of the 22 different types of strip parameters are evaluated on the fixed cylinder. Then, P5-60-20 (location alpha = 60 degrees, coverage beta = 20 degrees, and thickness h/D = 5%) is chosen to explore the transverse FIV. P5-60-20 vibration responses exhibit four distinct branches-initial branch, passive upper branch, transition branch from vortex-induced vibration (VIV) to galloping, and pure galloping-which correspond to the classic initial, upper, lower, and desynchronization regions of the circular cylinder. Through a detailed discussion of each branch, it is discovered that the passive upper branch is significantly different from the upper branch, despite their similar vibration amplitudes and frequencies. The upper branch is induced by the flutter in the presence of intense three-dimensional flow. However, the passive upper branch is caused by symmetric strips, which promote spanwise correlation, prevent lift phase shifting, and dampen the effect of three-dimensional flow. Consequently, at higher reduced velocities, the transition from VIV to galloping and pure galloping is triggered. Published under an exclusive license by AIP Publishing.