Experimental investigation of aerodynamic forces and vortex-induced vibrations of wavy cylinders at subcritical Reynolds numbers

Abstract

Wavy cylinders have been reported to exhibit satisfactory aerodynamic performance at low Reynolds numbers. However, aerodynamic characteristics are still ambiguous at higher Reynolds numbers. A series of wind tunnel tests were conducted for different wavy cylinders with Reynolds numbers (Re) from 0.75 × 104 to 2.00 × 105, including measurements of the overall aerodynamic forces, local surface static pressure, and vortex-induced vibrations (VIVs). The experiments yielded the following results. First, the mean drag and fluctuating lift coefficients of wavy cylinders were generally lower than those of a circular cylinder in the tested Re range. The maximum drag reduction was up to 18%. Second, a very slight waviness of a/D = 0.03 could improve aerodynamic performance, which could be taken as a reference for practical application. Third, the aerodynamic characteristics of wavy cylinders exhibited obvious three-dimensional (3D) features. This is reflected by various parameters varying along the spanwise direction. Fourth, the mechanisms of stronger 3D properties and less forces might be different. The former is dependent on the degree of obliqueness, while the latter is more related to the spanwise wavelength. Fifth, compared to a circular cylinder, the VIV amplitude was reduced and the lock-in range was shifted to higher wind velocities for wavy cylinders.