## 12.6. Summary

An overview of hybrid Scale-Resolving Simulation (SRS) technologies was given. Due to the nature of the subject, only a rough outline of the models could be provided. The rational and the advantages/disadvantages of each model family have been discussed. Based on the description of the models, an attempt has been made to categorize flows into sub-classes, and to map the modeling strategies onto these classes. It should be emphasized again, that the proposed categories are not easily and clearly defined and have significant overlap. Still it is considered necessary to explain that no single SRS model is suitable for all applications and it is not possible to generalize about which model should be used for which type of flow.

In principle, ELES and ZFLES, in combination with WMLES, are suitable for all flows, but require a substantial amount of preprocessing work to define the corresponding zones and provide suitable grids for all of them. For complex applications, this is not always feasible/practical, and global models (SAS, DDES, SDES, SBES) are favored. Studies have shown a clear superiority of the SBES model over all the other global hybrid RANS-LES formulations. The SBES model is therefore recommended for such applications. However, as detailed, all of these models work only if a sufficient level of instability is present in the flow. If in doubt, it is better to select the safer option over the more convenient one.

Details on many aspects of SRS have been provided, ranging from numerics, to grid resolution all the way to postprocessing. Numerous examples have been shown to enable the reader to properly place the intended application into this framework. It is anticipated that the document will evolve over time, as new questions are posed by users and as the SRS models themselves will evolve.

A brief summary of the more important points is provided in the Appendices.

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