Characteristics and mechanism investigation on drag reduction of oblique riblets

• Published in: Journal of Central South University Vol. 24; no. 6; pp. 1379 - 1386
• Main Authors: Gu, Yun-qing, Fan, Tian-xing, Mou, Jie-gang, Wu, Deng-hao, Zheng, Shui-hua, Wang, Evan
• Format: Journal Article
• Language: English
• Published: Changsha Central South University 01.06.2017; Springer Nature B.V
• Subjects: Boundary layers; Computational fluid dynamics; Computer simulation; Differential pressure; Drag reduction; Engineering; Fluid flow; Friction resistance; Inclination angle; Mathematical models; Metallic Materials; Pneumatics; Projects; Reynolds stress; Riblets; Shear stress; Stress concentration; Tips; Trailers; Turbulence; Viscosity; Vortices; drag reduction; Reynolds stress model (RSM); oblique riblets; secondary vortex; numerical simulation
• DOI: 10.1007/s11771-017-3542-5
• ISSN: 2095-2899

This work primarily focuses on the drag reduction characteristics and mechanism investigation of oblique riblets. First, a calculation model of the oblique riblets surface is established, and Reynolds stress model (RSM) turbulence model is used for numerical simulation of the oblique riblets flow field. Subsequently, the influence of inclination angle between flow direction and arrangement direction of riblets on friction resistance and drag reduction rate is further analyzed. Through the investigation of the distribution of shear stress, pressure stress and velocity in oblique riblets boundary layer, the oblique riblets drag reduction mechanism is finally revealed. Results show that, with increase of velocity and inclination angle, the pressure resistance increases obviously, along with the decreasing of the viscous resistance distinctly. The maximum drag reduction rate of the oblique riblets is 7.33%. Moreover, when the inclination angle increases, the wall shear stress reduces on oblique riblets surface; while differential pressure increases at both sides of oblique riblets tips. In addition, when inclination angle is small, the secondary vortex at oblique riblets tips will disappear soon. New vortices will be formed inside the oblique riblets and cause the decrease of viscosity resistance. Thus, oblique riblets show a better drag reduction effect and have an effective control on boundary layer.