LES turbulence models

Not all the turbulence models are based in the RANS approach mentioned in the previous section. In recent years a significant progress has been carried out in the development of new turbulence models based on the fact that not the entire range of scales of the flow is of interest for the majority of engineering applications. In this type of applications information contained in "the large scales" of the flow is enough to analyse magnitudes of interest as velocity, temperature,... Therefore, the idea that the global flow behaviour can be correctly approximated without the necessity to approximate the smaller scales correctly, is seen as a great advance in the modelling of turbulence. This fact has originated the design of turbulence models that describe the interaction of small scales with large scales. These models are commonly known as Large Eddy Simulation models (LES).

LES models are based on the regularization of the Navier Stokes equation, obtaining a stable (in some sense) formulation. The key idea of LES models is to find numerical schemes to solve problems based on a criterion of solution uniqueness, existence of a maximum principle, convergence to suitable solutions, or convergence in graph norm.