Experimental investigation on drag reduction of wavy cylinder in cross flow

The effects of different degrees of obliqueness of wavy cylinders on drag reduction on cylindrical structures were experimentally investigated. The experiments were carried out in a low speed wind tunnel with a cross-section of 0.6 m × 0.6 m and a free-stream turbulent intensity of less than 0.2%. The Reynolds numbers, based on the free-stream velocity and the nominal cylinder diameter, vary from about 2.0×10⁴ to 5.0×10⁴. Measurements on mean drag force induced by a cross flow over three wavy cylinders and the circumferential pressure distributions at various spanwise positions were conducted. The results show that the mean drag coefficients of the wavy cylinders are less than that of a corresponding circular cylinder; a drag reduction of up to 20% was obtained. Furthermore, the pressure distribution indicates that the pressure drop is more rapid and the separation is earlier at the geometric saddle than those at other spanwise locations for wavy cylinders. These effects become more evident as the degree of obliqueness increases.