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Topic | Classical or existing theory | Observation of our DNS |
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Turbulence generation | By “vortex breakdown” | Not by “vortex breakdown” but by shear layer instability |
First-ring generation | Self-induced, deformed, inclined, and pinched-off | By counter-rotated vortices interaction, circular, perpendicular, no pinch-off |
Multiple-ring structure | “Crow theory” or breakdown and then reconnected | No breakdown, not “Crow theory” but momentum deficit caused by ejection, vorticity conservation |
Multiple-level high shears | No report | By multiple-level sweeps and ejections |
Energy transfer channel, turbulence sustenance | Energy transfers from larger vortices to smaller one through “vortex breakdown” without dissipation until viscosity | From inviscid flow down to bottom by multilevel sweeps |
U-shaped vortex | Head wave, secondary vortex, by second sweep, newly formed, breakdown | Not head wave, tertiary vortex, by secondary vortex, existing from beginning, never breakdown |
Randomization | Background noise, starting from the top ring and then going down to the bottom | Internal property, starting from second level rings in the middle, affects bottom and then up to affect top rings. Loss of symmetry maybe caused by C-K shift |
Coefficients of friction | Turbulent flow has large friction due to strong boundary layer mixing | Depending only on velocity profile changes in laminar sublayer, no matter turbulent or laminar |
Richardson eddy cascade | Classical theory | Not observed |
Vortex breakdown | Classical theory | Not observed |
Kolmogorov scale | Classical theory | Smallest length scale should be determined by minimum shear layer instability |
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