Subgrid-scale modeling is spirit of large-eddy simulation. Original intention of rational subgrid-scale modeling is to remove empirical and phenomenological components of modeling process, so that every step in modeling process is physically and mathematically traceable. According to theory of rational subgrid modeling, we developed a series of subgrid models that do not depend on empirical constants and phenomenological models, but their effect in practical problems is still insufficient, which leads to, in recent years, reflection on proper idea of subgrid modeling. This paper reviews existing research and new progress, whose goal is to give a rational and self-consistent theoretical guidance of future large eddy simulation.

With DNS database,we study the triad interaction of scalar energy transfer,and make a multi-scale analysis in different scales.It shows that the energy transfer in scalar turbulence is different from that in velocity fluctuations.The major contribution of scalar transfer is given by large scale turbulence.Simulation of scalar turbulence requires a higher resolution.The interation between large scale velocity fluctuations and small scale scalar turbulence is an important part of the energy transfer.Non_energy transfer is as important as the local energy transfer in the scalar turbulence.We define an energy transfer coefficient,and find that the inertia_convective range in scalar turbulence is longer than the inertial subrange in turbulent kinetic transfer with same Re and Pe numbers.