Probability distribution, conditional dissipation, and transport of passive temperature fluctuations in grid-generated turbulence

• Jayesh

  Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York 14853

• Z. Warhaft

  Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York 14853

抄録

The evolution of the scalar probability density function (pdf), the conditional scalar dissipation rate, and other statistics including transport properties are studied for passive temperature fluctuations in decaying grid-generated turbulence. The effect of filtering and differentiating the time series is also investigated. For a nonzero mean temperature gradient it is shown that the pdf of the temperature fluctuations has pronounced exponential tails for turbulence Reynolds number (Rel) greater than 70 but below this value the pdf is close to Gaussian. The scalar dissipation rate, conditioned on the fluctuations, shows that there is a high expectation of dissipation in the presence of the large, rare fluctuations that produce the exponential tails. Significant positive correlation between the mean square scalar fluctuations and the instantaneous scalar dissipation rate is found when exponential tails occur. The case of temperature fluctuations in the absence of a mean gradient is also studied. Here, the results are less definite because the generation of the fluctuations (by means of fine heated wires) causes an asymmetry in the pdf. The results show, however, that the pdf is close to Gaussian and that the correlation between the mean square temperature fluctuations and the instantaneous scalar dissipation rate is very weak. For the linear profile case, measurements over the range 60≤Rel≤1100 show that the dimensionless heat flux Nu is proportional to Rel0.88 and that the transition from a Gaussian pdf to one with exponential tails occurs at Nu∼31, a value close to transitions observed in other recent mixing experiments conducted in entirely different turbulent flows.

収録刊行物

• Physics of Fluids A: Fluid Dynamics

  Physics of Fluids A: Fluid Dynamics 4 (10), 2292-2307, 1992-10-01

  AIP Publishing

キーワード

• General Engineering

詳細情報

• CRID: 1360292619264700800
• NII論文ID: 80006708180
• NII論文ID: 30015997865
• NII書誌ID: AA00773996
• DOI: 10.1063/1.858469
• ISSN: 08998213
• Web Site: https://pubs.aip.org/aip/pof/article-pdf/4/10/2292/12559525/2292_1_online.pdf
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