The fluid-induced vibration of cylinders with non-circular cross-sections in a water channel

Geometry is one of the most significant parameters in fluid-structure interaction problems. The circular cylinder is the most widely investigated geometry in the field of Fluid-Induced Vibration (FIV). This study experimentally studied FIV of rigid cylinders with two different cross-sections (extracted from a circular cylinder profile). To shed some light on the FIV in the present study, two geometries of non-circular cylinders in various configurations are investigated in terms of amplitude and frequency ratio compared to the circular cylinder. The geometries are a D-shaped section cylinder and a cylinder consist of a semi-circle and an isosceles triangle section. The experiments have been conducted in a towing-tank water channel over a Reynolds number of 1.5x10(4) < Re < 8x10(4). Cylinders with the symmetrical side view to the fluid direction experienced Vortex Induced Vibration (VIV) phenomenon, while the D-shaped cylinder in the Upside-Down configuration could not reach themaximum amplitude ratio more than 0.3 within a small range of reduced velocities. The results indicate that cylinders with circular shapes in front of the flow and different after bodies have a wider synchronization range but a lower peak amplitude ratio than the circular cylinder. Also, all VIV of cylinders have a delay at the beginning of the initial branch, especially in the case with a circular shape in front and a triangular edge located on the back. Among the bluff bodies, VIV of the Triangular Front-edge Cylinder only consists of lower and upper branches without a desynchronization. Furthermore, similar high-amplitude frequencies are observed in cylinders with the same circular geometry approaching the fluid flow.