Spanwise Characteristics of Flow Crossing a Yawed Circular Cylinder of Finite Length

The spanwise characteristics of flow passing a yawed finite circular cylinder are numerical investigated at the yaw angle of 30°, aspect ratio of 9 and Reynolds number of 3900 using Large Eddy Simulation. The wake vortical structure and streamlines manifest that the regular Karman vortex street breaks down and there exists axial flow along the cylinder axis. To get further insight into the spanwise characteristics, the cylinder is virtually divided into nine equal-spaced sections along the cylinder span, and the drag and lift force coefficients of each section are monitored. By comparing the drag coefficients of these nine cylinder sections, it is found that the anti-clockwise torque is imposed on the cylinder. Furthermore, the FFT analyses of these nine fluctuating lift coefficients are carried out to reveal the characteristics in the frequency domain. It is shown that the nine spectra demonstrate different behaviours, by which the wake vortical structure is identified spanwise as three regions, two end-plate regions and the midspan region. In the downstream end-plate region, the vortex-shedding is well organized, whereas in the upstream end-plate region the wake vortex structure manifests itself stronger three-dimensional and severely irregular. And in the midspan region, the peak of frequency spectra is broadband and the regular Karman vortex street is not yet noticeable to identify.