湍流大涡数值模拟进展

本文简要陈述湍流大涡数值模拟的原理、优点,着重讨论湍流大涡数值模拟方法的关键问题及其可能解决的途径,包括脉动的过滤、亚格子模型、近壁模型和标量湍流的大涡数值模拟中的特殊问题.文章强调大涡数值模拟中亚格子应力的本质是可解尺度湍流和不可解尺度湍流动量间的输运,并以作者最近提出的新型亚格子模型说明发展亚格子模型的正确途径.文章最后提出湍流大涡数值模拟近期需要迫切解决的问题和其他具有挑战性的方向.

Progress in large eddy simulation of turbulent flows

The paper introduces the principles of LES for turbulence and its advantage. Authors focuses on the existing problems in LES and the way of their solution, such as the filters, subgrid modeling, near-wall models and scalar turbulence. The communicative error of inhomogeneous filter is mentioned and the method of its reduction is recommended. (Existing) subgrid models are introduced with evaluation of their feasibility. The importance of near-wall model in LES for wall-bounded flows with large Reynolds number is mentioned; and algebraic model and wall boundary layer model are introduced with experimental and numerical comparison. The problem of scalar turbulence is put forward in the paper that the mass transportation of scalar turbulence strongly depends on the molecular diffusivity at fixed Reynolds number when the ratio of molecular viscosity to molecular diffusivity, Prandtl number for instance, is less than 1. The authors emphasize that the turbulent transportation between resolved and unresolved turbulence in LES is the fundamental mechanism of subgrid stress and subgrid scalar flux, hence inclusion of correct transportation mechanism in modeling is the proper way of establishing subgrid model. The authors propose a new subgrid stress model based on the Kolmogorov equation for resolved turbulence, in which the mass or momentum transportation between resolved and unresolved turbulence is included. The new model is tested in both isotropic and shear turbulence. The predicted statistical properties in a turbulent channel flow are in good agreement with DNS results up to Re=590.