Statistics of conditionally filtered dissipation and diffusion in large eddy simulation
大涡模拟中的条件滤波耗散和扩散的统计特性

In the large eddy simulation of turbulent reacting flows, the filtered reaction terms are unclosed. It is difficult to construct the subgrid scale (SGS) model for filtered reaction terms due to the absence of a universal energy cascade process, which is the foundation of SGS models in fluid turbulence. With the conditional filter approach, the SGS models for conditionally filtered reaction terms can be closed, but the conditional diffusion and dissipation have to be modeled. We use a direct numerical simulation of turbulent mixing to investigate the scale-dependence of the conditional filtered diffusion and dissipation. The results show that the conditional filtered diffusion depends on large scales, but the conditional filtered dissipation depends on both large and small scales. The effects of small scales on the conditional filtered dissipation have to be included in its SGS models.