Assessment of two-equation models of turbulent passive-scalar diffusion in channel flow
Assessment of two-equation models of turbulent passive-scalar diffusion in channel flow
复制标题
通道流中湍流被动标量扩散二方程模型的评估
DOI：
10.1017/s0022112092001769
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发表时间：
1992
影响因子：
3.7
通讯作者：
K. Horiuti
中科院分区：
文献类型：
--
作者：
K. Horiuti
利用基于Navier-Stokes方程数值解的数据库研究了紊流中被动标量的输运模型，这些数据库是利用大涡和直接数值模拟技术生成的。通过与Hishida的实验测量值的比较，证实了其可靠性。Nagano & Tagawa（1986）。本文使用Nagano & Kim（1988）的标量方差（kθ）和标量方差耗散（εθ）的“双方程”模型对这些模拟和计算进行了比较。该模型通过用速度和标量波动的时间尺度之比来表示涡流扩散率，从而解释了流量对普朗特数的依赖关系。然而，Yoshizawa（1988）的统计分析表明，Nagano-Kim模型中各向同性涡旋扩散率的定义不一致，本文使用大涡旋模拟和直接数值模拟（LES/DNS）数据库计算两种模型中包含的量的结果清楚地表明了这一含义。提出了Nagano-Kim模型的扩展，解决了这些不一致之处，并给出了该模型的进一步发展，其中计算了各向异性标量通量。在刚性表面附近，标量通量的三阶“各向异性表示”可以用作降低涡流扩散率的替代模型，而不是传统的“阻尼函数”。该模型与Rogers， Mansour & Reynolds（1989）的代数标量通量模型相似，但又有所不同。本文的第三个方面是使用LES/DNS数据库来评估另一种类似类型模型的某些系数（为压力-标量梯度项建模的系数），即Launder（1975）的代数标量通量模型。
Models for the transport of passive scalar in turbulent flow were investigated using databases derived from numerical solutions of the Navier—Stokes equations for fully developed plane channel flow, these databases being generated using large-eddy and direct numerical simulation techniques. Their reliability has been established by comparison with the experimental measurements of Hishida. Nagano & Tagawa (1986). The present paper compares these simulations and calculations using the Nagano & Kim (1988) ‘two-equation’ model for the scalar variance (kθ) and scalar variance dissipation (εθ). This model accounts for the dependence of flow quantities on the Prandtl number by expressing eddy diffusivity in terms of the ratio of the timescales of velocity and scalar fluctuations. However, the statistical analysis by Yoshizawa (1988) showed that there was an inconsistency in the definition of the isotropic eddy diffusivity in the Nagano—Kim model, the implications of which are clearly demonstrated by the results of this paper where large-eddy simulation and direct numerical simulation (LES/DNS) databases are used to compute the quantities contained in both models. An extension of the Nagano-Kim model is proposed which resolves these inconsistencies, and a further development of this model is given in which the anisotropic scalar fluxes are calculated. Near a rigid surface, a third-order ‘anisotropic representation’ of scalar fluxes may be used as an alternative model for reducing the eddy diffusivity, instead of the conventional ‘damping functions’. This model is similar but distinct from the algebraic scalar flux model of Rogers, Mansour & Reynolds (1989). A third aspect of this paper is the use of the LES/DNS databases to evaluate certain coefficients (those for modelling the pressure-scalar gradient terms) of another model of a similar type, namely the algebraic scalar flux model of Launder (1975).