Force and flow characteristics of a circular cylinder with uniform surface roughness at subcritical Reynolds numbers. (January 2015)

• Record Type: Journal Article
• Authors: Zhou, Bo; Wang, Xikun; Gho, Wie Min; Tan, Soon Keat
• Is Part Of: Applied ocean research. Volume 49(2015:Jan.)
• Page Start: 20
• Page End: 26
• Publication Date: 2015-01
• Subjects: Drag coefficient -- Drag reduction -- Surface roughness -- Rough cylinder -- Dimple cylinder; Ocean engineering -- Periodicals; 620.416205
• DOI: 10.1016/j.apor.2014.06.002
• Languages: English
• ISSNs: 0141-1187

Abstract

Highlights: The aim is to understand the relationship of drag reduction and surface roughness. The flow field around the cylinder was measured using Particle Imaging Velocimetry. The certain surface roughness significantly reduces the mean drag coefficient. The r.m.s. lift coefficient of rough cylinder is lower than that of smooth cylinder. Abstract: The main purpose of this study is to establish a better understanding of the relationship between drag reduction and surface roughness. Experiments were conducted to measure the force and flow characteristics of a circular cylinder with different types of artificial surface roughness over the range 6 × 10 3 < Re < 8 × 10 4 ( Re is based on the cylinder diameter D ). The roughness cylinder was formed by covering the exterior surface of the cylinder with uniformly distributed (1) sandpaper, (2) netting, and (3) dimples. The roughness coefficient ranged from k / D = 0.0028 to 0.025 ( k is the roughness height). A detailed quantitative measurement of the flow field around the cylinder using Particle Imaging Velocimetry (PIV) was carried out. The hydrodynamic force coefficients (drag and lift) of the rough cylinders are compared against those of a smooth cylinder measured under the same flow conditions. It is found that certain configuration of surface roughness significantly reduces the mean drag coefficient of the cylinder, particularly at large Reynolds numbers. In addition, the root-mean-square (r.m.s.) lift coefficient of the rough cylinders is considerably lower than that of a smooth cylinder.