LES (Large Eddy Simulation) is a method used to numerically simulate turbulence and is an intermediate method between DNS (Direct Numerical Simulation) and RANS (Reynolds-Averaged Navier-Stokes -Stokes equations).The main idea of the LES method is to decompose the turbulent field, dividing the large scale eddies into parts that can be directly simulated or treated explicitly, while the small scale eddies are considered negligible and their effects are described by a parametric model.

The main features of the LES large eddy simulation can be summarized as follows:

     ￮ Simulation scale: In LES simulations, the focus of large eddy simulations is on resolving the dynamical properties of large scale eddies at high time resolution. It is usually applied to medium to high Reynolds number turbulence (Reynolds number) cases, where the turbulence scales range between a few to tens of grid scales.

     ￮ Vortex partitioning: The LES approach attempts to decompose the flow field into large, medium, and small scale flows, treating small scale vortices as being viscous dissipative and unresolvable, while more importantly understanding large scale vortices in depth and describing their dynamics, and small scale vortices have their effects modeled by methods such as subgrid scaling with representative volume elements.

     ￮ Parametric models: In the LES approach, different models are used to describe the small-scale vortex effects in the computational domain, such as wall functions, flow transitions, etc. These models include Smagorinsky model, WALE model, Vreman model, etc. These models can be linear or nonlinear, depending on the specific model used.

     ￮ Integration time scale: The appropriate integration time scale should be chosen according to the characteristics of the problem and the vortex scale. Unlike DNS, LES uses high time resolution to resolve large vortices, but it is still necessary to select the appropriate vortex integration time scale to determine the small vortices described by the model. Choosing the appropriate integration time scale ensures the accuracy and reliability of the results obtained from LES.

      In conclusion, LES large eddy simulation is a widely used method for numerical simulation of turbulence. Its unique strategy of large scale simulation and small scale vortex model parameterization enables it to better characterize turbulent dynamics and has been widely used in many CFD applications.