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Meandering of a wing-tip vortex in a grid-generated turbulent flow
- Source :
- Physics of Fluids. 33:115131
- Publication Year :
- 2021
- Publisher :
- AIP Publishing, 2021.
-
Abstract
- The interaction of a National Advisory Committee for Aeronautics 0012 wing-tip vortex with a grid-generated turbulent flow was experimentally investigated. The experiments were conducted in the near- and mid-wake regions at three free-stream turbulence (FST) levels, viz., 0.5%, 3%, and 6%, at a Reynolds number, based on the wing chord length, cw, of 2×105. Stereoscopic particle image velocimetry measurements were carried out at four downstream positions: x/cw = 1.25, 3.25, 6.25, and 7.75. Streamwise vorticity contours showed that the wing-tip vortex decayed with increased FST and downstream distance. Turbulent surroundings were found to affect the meandering amplitude of the vortex, which increased with the dispersed scatter pattern of the vortex center motion, resulting in a meandering-induced turbulence. Meandering-corrected turbulent kinetic energy revealed the existence of a laminar core at the center of the vortex surrounded by low turbulence levels outside the core. This was attributed to the stabilizing Coriolis effects of the strong rotational motion inside the vortex core, which tend to re-laminarize the turbulent fluid crossing the periphery of the vortex. Snapshot proper orthogonal decomposition analysis on the coherent component of the velocity field revealed two dominant modes forming a helical dipole, consistent with the helical displacement of a Kelvin wave with an azimuthal wavenumber |m=1|. An analysis of the terms balancing the rate of decay of the mean enstrophy revealed that increasing FST increases the stretching of the mean enstrophy within the vortex core while it reduces both its transport and convection terms. Nonetheless, the latter contributions were larger in all cases studied acting as the main mechanism for mean enstrophy decay.
- Subjects :
- Fluid Flow and Transfer Processes
Physics
020301 aerospace & aeronautics
Turbulence
Mechanical Engineering
Computational Mechanics
Reynolds number
Laminar flow
02 engineering and technology
Mechanics
Vorticity
Condensed Matter Physics
Enstrophy
01 natural sciences
010305 fluids & plasmas
Vortex
Physics::Fluid Dynamics
symbols.namesake
0203 mechanical engineering
13. Climate action
Mechanics of Materials
0103 physical sciences
Turbulence kinetic energy
symbols
Kelvin wave
Subjects
Details
- ISSN :
- 10897666 and 10706631
- Volume :
- 33
- Database :
- OpenAIRE
- Journal :
- Physics of Fluids
- Accession number :
- edsair.doi...........f647d68013ee33943f9cefac0ed4974b