Large Eddy Simulation of Flow over a Twisted Elliptic Cylinder at a Subcritical Reynolds Number

摘要

The wavy cylinder has a sinusoidal variation in cross sectional area along the spanwise direction and the torsional cylinder has been newly designed by rotating the elliptic cross section along the spanwise direction, so that the cylinder surface has a twisted spiral pattern. For an ellipse, different eccentricities are considered to observe the effect of eccentricity on the flow fields. It guarantees the accuracy of the present numerical methods that the excellent comparisons with previous studies for the cases of a smooth circular cylinder and a wavy cylinder. The effect of surface torsion which is newly designed in here has been predicted and assessed in terms of the mean drag and root-mean-square (RMS) value of fluctuating lift in the subcritical Reynolds number range. Subsequently, the mechanisms of enhancing the aerodynamic performance and passive control of vortex-induced vibrations are also investigated by careful analysis with the flow structures. The isosurface of swirling strength has been imposed to identify the vortical structures in the turbulent wake.