### 4.1.13. The Stress-Blended Eddy Simulation (SBES) Model

One of the weaknesses of the original DES model family is that it shields attached boundary layers insufficiently from the impact of the grid-dependent term. For this reason, the Stress Blended Eddy Simulation (SBES) model has been developed. This model features a much improved shielding function to protect RANS boundary layers.

The SBES model uses that shielding function, which is also utilized to switch to an existing algebraic LES model in the LES zone. The advantage is that you can clearly distinguish where the RANS and LES zones are (by visualizing the shielding function) and which model is used in which zone. Because SBES blends between two existing models, it is not a true turbulence model, but rather an automated way of switching between existing RANS and LES models. The switching function is unpublished.

The SBES model “transitions” much quicker from RANS to Scale Resolving Simulation (SRS) mode in separating shear layers. This leads to more realistic solutions with higher internal consistency. In addition, this model allows for a RANS-LES “transition” on much coarser grids than classical DES.

For SBES implementation details, see Stress-Blended Eddy Simulation (SBES) in the CFX-Solver Theory Guide.

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