Journal of Fluid Science and Technology
Online ISSN : 1880-5558
ISSN-L : 1880-5558
Papers
Redefining Mixing Length in Turbulent Mixing Layer in Terms of Shear-Induced Vorticity
Keh-Chin CHANGChiuan-Ting LI
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2011 年 6 巻 4 号 p. 662-673

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An incompressible turbulent planar mixing layer is composed of two different flow types in its flow field, namely a shear layer in the central region and two free streams in each outer high- and low-speed sides. Shear layer is formed right after the trailing edge of the splitter plate and develops stream-wisely through successively distinct regions, namely the near field region and the self-preserving region. A new definition of the mixing length (lω) is proposed on the basis of an effectively pure shear-induced vorticity component (ΩSH) by means of a triple decomposition method, that is, lω = yH - yL where yH and yL are the two transverse positions, at which |ΩSH| normalized with the maximum ∂U/∂y at the virtual origin is equal to 0.05, in the high- and low-speed free stream sides, respectively. It is shown that the linear growth rate of lω along stream-wise distance can be, then, used as one of the necessary and sufficient conditions for identifying the achievement of the self-preserving state in turbulent mixing layer.

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© 2011 by The Japan Society of Mechanical Engineers
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