Abstract
In this study, the drag reduction effect is studied for a cylinder with different V-groove depths on its surface using a k-ω/SST (Shear Stress Transport) turbulence model of computational fluid dynamics (CFD), while a particle image velocimetry (PIV) system is employed to analyze the wake characteristics for a smooth cylinder and a cylinder with different V-groove depths on its surface at different Reynolds numbers. The study focuses on the characteristics of the different V-groove depths on lift coefficient, drag coefficient, the velocity distribution of flow field, pressure coefficient, vortex shedding, and vortex structure. In comparison with a smooth cylinder, the lift coefficient and drag coefficient can be reduced for a cylinder with different V-groove depths on its surface, and the maximum reduction rates of lift coefficient and drag coefficient are about 34.4% and 16%, respectively. Otherwise, the vortex structure presents a complete symmetry for the smooth cylinder, however, the symmetry of the vortex structure becomes insignificant for the V-shaped groove structure with different depths. This is also an important reason for the drag reduction effect of a cylinder with a V-groove surface.
Highlights
Flow around a cylinder has always been a classical problem in the field of fluid mechanics, one which contains complex flow phenomena such as flow separation, vortex shedding, and wake evolution
The width of the wake flow for the smooth cylinder is larger than the cylinder with the different V-groove surface depths
A V-shaped groove surface with different depths is arranged on a cylinder surface, while a computational fluid dynamics (CFD) k-ω/stress transport (SST) turbulence model and particle image velocimetry (PIV) technology are employed to study the drag reduction effect and wake characteristics
Summary
Flow around a cylinder has always been a classical problem in the field of fluid mechanics, one which contains complex flow phenomena such as flow separation, vortex shedding, and wake evolution. Oruc et al [12] used PIV to demonstrate the vortex structure of a single-cylinder wake region with different Reynolds numbers that arose due to the shear layer decoupling from the cylindrical surface. It was proved by investigating the vorticity, Reynolds stress and turbulent energy of the flow field that arranging a water droplet-shaped mesh structure around the cylinder suppresses the formation of a vortex during the flow around the cylinder. The drag reduction effect and wake characteristics are studied for a cylinder with different V-groove depths on its surface using a k-ω/SST turbulence model of computational fluid dynamics (ANSYS 15.0, Customer # 503068) and particle image velocimetry (PIV) technology at the different Reynolds numbers. Δij is the Kronecker delta symbol, and −ρuiuj is the Reynolds stress term, which leads to the equations being unclosed, so a turbulence model is needed to close the stress term
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