A dynamic subgrid-scale (SGS) scalar-flux model, based on the exact rate of production of turbulent scalar fluxes, is proposed. The model is derived from an assumption that the pressure-scalar correlation in the equation for turbulent scalar flux is a vector that is approximately aligned with the scalar flux itself. The formulation then yields a tensor diffusivity which allows nonalignment of the SGS scalar fluxes with respect to the resolved scalar gradient. In contrast to eddy diffusivity models and to general gradient diffusion hypothesis models, for which the diffusivity tensor is symmetric, the present formulation produces an asymmetric diffusion tensor; for theoretical and experimental reasons, that tensor is known to be very asymmetric. The model contains a single coefficient, which is determined dynamically. The model is validated in fully developed turbulent channel flow and in separated and reattaching flow over a backstep.

中文翻译：

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基于精确的湍流产生速率的动态亚网格标量通量模型

提出了一种基于湍流标量通量精确产生速率的动态亚网格标度（SGS）标量通量模型。该模型是基于以下假设得出的：湍流标量通量方程中的压力-标量相关性是一个与标量通量本身近似对齐的矢量。然后，该制剂产生张量扩散率，该张量扩散率允许SGS标量通量相对于解析后的标量梯度不对齐。与涡度扩散张量是对称的涡流扩散模型和一般梯度扩散假设模型相反，本公式产生了非对称扩散张量。由于理论和实验的原因，已知张量非常不对称。该模型包含一个动态确定的系数。