Detached Eddy Simulation coupled with steady RANS in the wall region

Paper in proceeding, 2021

Xiao & Jenny (2012) proposed an interesting hybrid LES/RANS method in which they use two solvers and solve the RANS and LES equations in the entire computational domain. In the present work this method is simplified and used as a hybrid RANS-LES method, a wall-modeled LES.
The two solvers are employed in the entire domain. Near the walls, the flow is governed by the steady RANS solver; drift terms are added to the DES
equations to ensure that the time-integrated DES fields agree with the steady RANS field. Away from the walls, the flow is governed by the DES
solver; in this region, the RANS field is set to the time-integrated LES field. The disadvantage of traditional DES models is that the RANS models
in the near-wall region – which originally were developed and tuned for steady RANS – are used as URANS models where a large part of the turbulence is resolved. In the present method – where steady RANS is used in the near-wall region – the RANS turbulence models are used in a context for which they were developed. In this method, it may be worth while to use an accurate, advanced RANS model. The EARSM model is used in the steady RANS solver. The new method is called NZ S-DES . It is found to substantially improve the predicting capability of the standard DES. A great advantage of the new model is that it is insensitive to the location of the RANS-LES interface.