Multiscale turbulence
Multiscale turbulence is a class of
As turbulent flows contain eddies with a wide range of scales, exciting the turbulence at particular scales (or range of scales) allows one to fine-tune the properties of that flow. Multiscale turbulent flows have been successfully applied in different fields.,[6] such as:
- Reducing
- Enhancing heat transfer from impinging jets passing through grids;[8]
- Reducing the vortex shedding intensity of flows past normal plates without changing the shedding frequency;[9]
- Enhancing mixing by energy-efficient stirring;[10][11]
- Improving flow metering and flow conditioning in pipes;[12]
- Improving combustion.[13][14]
Multiscale turbulence has also played an important role into probing the internal structure of turbulence.[15] This sort of turbulence allowed researchers to unveil a novel dissipation law in which the parameter in
is not constant, as required by the Richardson-Kolmogorov energy cascade. This new law[15] can be expressed as , with , where and are Reynolds numbers based, respectively, on initial/global conditions (such as free-stream velocity and the object's length scale) and local conditions (such as the rms velocity and integral length scale). This new dissipation law characterises non-equilibrium turbulence apparently universally in various flows (not just multiscale turbulence) and results from non-equilibrium unsteady energy cascade. This imbalance implies that new mean flow scalings exist for free shear turbulent flows, as already observed in axisymmetric wakes[15][16]
References
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- ^ Nedić, J., B. Ganapathisubramani, J. C. Vassilicos, J. Boree, L. E. Brizzi, A. Spohn. "Aeroacoustic performance of fractal spoilers". AIAA journal 2012.
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- S2CID 119569184.
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- S2CID 93650086.
- ^ .
- ISSN 0022-1120.