II Presentation of Modelling Approaches

Abstract

The present chapter briefly summarises a progress in DES modelling reached in the course of DESider. In the introduction we outline a motivation for development of the hybrid RANS-LES methods, in general, and a place of DES and DES-like models within this rather wide group of turbulence resolving approaches, particularly. Then, in Section 1.2, the original DES formulation is presented together with a general approach to building DES versions based on different background RANS models and a list of such versions used or developed in DESider. Finally, Sections 1.3 and 1.4 describe two more general modifications not related to any specific background model and touching upon the basics of DES. They are Delayed DES (DDES) and Improved DDES (IDDES), which permit respectively to eliminate major flaws of the “standard” DES found in the course of its intensive use both within and outside DESider and to widen an area of DES applicability.