A finite cantilevered cylinder in a cross-flow

Abstract

Numerous factors contribute to the three-dimensional behavior of the wake behind a finite cylinder with relatively large aspect ratio in a cross flow; among the more important ones are the trailing vortex shed from the free end and the necklace vortex formed at the cylinder base. The trailing vortex interacts strongly with the flow around the cylinder; thus giving rise to oblique vortex shedding and changes the flow structures, such as the vortex pattern, and the pressure distribution around the cylinder. Formation of a necklace vortex near the base of the cylinder could give rise to interaction between this vortex and the shed vortices along the cylinder span. Besides, the necklace vortex could even interact with the trailing vortex, depending on the cylinder aspect ratio. For aspect ratios greater than a critical value a suppressed two-dimensional region exists with vortex shedding resembling the Karman vortex street. In this paper, a lattice Boltzmann method is used to numerically simulate the flow past a finite cylinder with an aspect ratio of 10 at Reynolds numbers (Re) varying from 100 to 200. A major finding is that, even in this limited Re range, the wake behavior and flow-induced forces are greatly affected by Re. A suppressed two-dimensional region exists but its size decreases as Re increases. In addition, the effects of the trailing and necklace vortices on the variation of the Strouhal number, and the mean and root mean square drag and lift coefficients along the span are found to be affected by Re.