スパン方向の温度勾配を有する平行平板間乱流の直接数値シミュレーション : 乱流統計量に関する検討

概要

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Direct numerical simulation was performed for a turbulent channel flow where the time mean temperature has a spanwise gradient. As the first step of succesive investigations, turbulence statistics related to the spanwise heat transfer were examined. A computational code based on the finite difference scheme was developed for this purpose. The calculated statistics on the flow field were found to be in good agreement with the result of the existing direct numerical simulation by Kasagi et al. (1992). The eddy diffusivity ratio, ε_<nz>/ε_m and the Reynolds normal stress ratio, <ω^2>^^^-/<υ^2>^^^- show rapid increase toward the wall, as pointed out by Maekawa et al. (1991). However, the rapidincrease region of the ε_<nz>/ε_m was nearer to the wall than the Maekwa's result and found to roughly agree with that of the <ω^2>^^^-/<υ^2>^^^-. This result implies that, in the near-wall region, the spanwise turbulent heat flux per its production rate shows rough agreement with the wall-normal turbulent heat flux per its production rate. In addition, two point correlation coefficient, Q_<wθ> also agrees with Q_<vθ> in the range of y^+<75. In these points, the heat transfer in the present case has some analogy with that in the heated-wall case. Moreover, the budget of the spanwise turbulent heat flux was examined. It was found that the budget shows near local equilibrium except for the near-wall region.
社団法人日本機械学会の論文
1998-03-25