Experimental investigation of the mean and fluctuating forces of wavy (varicose) cylinders in a cross-flow

The effects of surface waviness of wavy (varicose) cylinders on mean drag and fluctuating lift reduction were experimentally investigated. The experiments were carried out in a low speed wind tunnel having a 0.6 m x 0.6 m cross-section and a free-stream turbulence intensity less than 0.2%. The Reynolds numbers, based on the free-stream velocity and the nominal cylinder diameter, vary from about 2.0 x 10(4) to 5.0 x 10(4). Measurements on mean and fluctuating forces induced by a cross-flow over three wavy cylinders and the circumferential pressure distributions at various spanwise positions are presented. From these results, it can be concluded 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. It was also found that the root-mean-square fluctuating lift coefficients of the wavy cylinders are much lower than those of a circular cylinder. However, the spectral analysis of both hot-wire and load cell signals show that the Strouhal numbers of the wavy cylinders are essentially the same as a corresponding circular cylinder. (C) 2004 Elsevier Ltd. All rights reserved.