游加平, 卢臻, 杨越. 湍流预混燃烧中的非各向同性速度统计与涡面结构[J]. 空气动力学学报, 2020, 38(3): 603-610. DOI: 10.7638/kqdlxxb-2019.0156
引用本文: 游加平, 卢臻, 杨越. 湍流预混燃烧中的非各向同性速度统计与涡面结构[J]. 空气动力学学报, 2020, 38(3): 603-610. DOI: 10.7638/kqdlxxb-2019.0156
YOU Jiaping, LU Zhen, YANG Yue. Anisotropic velocity statistics and vortex surfaces in turbulent premixed combustion[J]. ACTA AERODYNAMICA SINICA, 2020, 38(3): 603-610. DOI: 10.7638/kqdlxxb-2019.0156
Citation: YOU Jiaping, LU Zhen, YANG Yue. Anisotropic velocity statistics and vortex surfaces in turbulent premixed combustion[J]. ACTA AERODYNAMICA SINICA, 2020, 38(3): 603-610. DOI: 10.7638/kqdlxxb-2019.0156

湍流预混燃烧中的非各向同性速度统计与涡面结构

Anisotropic velocity statistics and vortex surfaces in turbulent premixed combustion

  • 摘要: 尽管统计局部各向同性假设已广泛用于湍流理论和建模,但湍流预混火焰的局部释热会令附近流体密度与黏性发生突变,进而使湍流流场呈现非各向同性统计。我们将涡面场方法推广于湍流预混燃烧,用于表征非各向同性涡面结构。发现未燃侧的小尺度缠绕扭曲涡管在火焰区受到热膨胀的拉伸作用,在已燃侧融合为大尺度块状结构。结合拟涡能输运方程和雷诺应力Lumley三角形,分析发现从未燃侧到已燃侧速度场非各向同性程度逐步增加,且涡面几何结构的变化与速度场局部非各向同性统计高度相关。

     

    Abstract: Although the hypothesis of statistically local isotropy has been extensively applied to turbulence theory and modeling, the heat release near turbulent premixed flames can significantly change the fluid density and viscosity, leading to anisotropic statistics in turbulent flow fields. We extend the vortex-surface field (VSF) to characterize anisotropic vortex surfaces in turbulent premixed combustion. We find that a tangle of twisted vortex tubes on the unburnt side are stretched along the streamwise direction near the flame front owing to the thermal expansion, and the small-scale vortex tubes gradually merge into large-scale bulky structures on the burnt side. By analyzing the enstrophy transport equation and the Lumley triangle of Reynolds stresses, we find that the anisotropy of velocity fields increases from the unburnt to the burnt side. Thus, the variation of the geometry of vortex surfaces near the flame front is highly correlated to the anisotropic statistics of the fluctuating velocity.

     

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