基于火焰面的大涡模拟中条件标量耗散率的模型

Models of the Conditional Scalar Dissipation Rate in Flamelet-Based Large Eddy Simulations

评估了映射封闭模型、对撞流模型、来自均匀湍流PDF输运方程的模型和一个唯象模型.结果表明,虽然映射封闭模型和对撞流模型使用不同的方法推导,并且具有不同的形式,但它们给出了完全一样的结果.在均匀湍流中,当标量方差很大时,映射封闭模型和对撞流模型给出的结果非常接近精确解,然而在标量方差很小或者当量位置的标量值和标量平均值之间存在很大差异时,映射封闭模型和对撞流模型不符合物理实际.这些结论通过直接数值模拟的结果来验证.

Various models of the conditional scalar dissipation rate are evaluated, including a mappingclosure model, a model using counterflow assumptions, a model from the homogeneous transport PDF equations, and a phenomenological model. It is found that the mappingclosure and the counterflow models give exactly the same results, even though they have different forms and are derived from different approaches. It is also found that the results from the mapping closure model and the counterflow model are very close to the exact solutions in homogeneous turbulence when the scalar variance is significant. On the other hand, the mapping closure model and the counterflow model misrepresent the physics when the scalar variance is small or the stoichiometric scalar value is significantly different from the scalar mean value. These results are validated by the a priori tests.