Low-Frequency Variations of Force Coefficients on Square Cylinders with Sharp and Rounded Corners

Abstract

Square lighting poles with sharp or round corners have been observed to exhibit large amplitude oscillations with a frequency that is near that of their first mode. This frequency is one order of magnitude lower than that of the vortex shedding frequency for the observed wind speeds. As such, lock-in resonance between the vortex shedding and the poles motions has been ruled out as the cause of these oscillations. In this work, numerical simulations on square cylinders with different aspect ratios and cross-sectional shapes have been carried out to explore and quantify low-frequency variations of the aerodynamic forces and their sources. The results show that low frequency components are a basic aspect of the flow over finite length cylinders and are associated with the three-dimensional flow characteristics near the free end of the cylinder. This aspect is related to the loss of synchronization of the vortex shedding which, in turn, results in variations of the mean drag coefficient along the cylinder.

Vortex Shedding Suppression: A Review on Modified Bluff Bodies

“…Carassale and Freda [45] investigated the influence of corner modification on the aerody- Some researchers combined the effect of corner modification with other parameters on the wake flow. Mola and Bordonaro [44] numerically studied flows over square cylinders with different aspect ratios and cross-sectional shapes to investigate aerodynamic forces variations. As flow over finite length cylinders exhibit 3D characteristics close to the free end region, a low frequency component has been observed.…”