A new RANS concept has been introduced. The new model is termed Generalize model (GEKO). It is based on a model platform and is designed to consolidate RANS turbulence models in Ansys CFD. Instead of offering a wide range of different models, it is the goal to provide a single model, with the flexibility to adjust it to a wide range of generic flow conditions and applications.

Flexibility within GEKO is achieved by augmenting the model with free coefficients, which can be adjusted by the user without the danger of violating the basic model calibration for conventional free shear flows and boundary layers. This allows the user to tune the model in a safe parameter space without the need for expert knowledge in turbulence modeling. In other words, instead of switching between a large number of existing turbulence model to find the optimal one for a given application, the user can now stay within one model framework and simple adjust the free coefficients. The model is designed such that the modification of the coefficients allows coverage of a wide solution space (actually a wider space than by switching between existing models).

In addition to being able to adjust the model coefficients, GEKO offers the advantage that the variation of coefficients is much more transparent than the change between different models. By changing from one model to another (say from SST to ) one does not only switch the model but also numerous other settings (e.g. different limiters, different wall treatment, …). Such changes might have an additional large effect on the solution without being transparent to the user. Finally, not all options/extensions are compatible with all turbulence models. Case in point is that models for laminar-turbulent transition are not compatible with existing models. A model user who wants to add transition physics, will therefore need to first switch to a model and then activate the transition model. It will then be difficult to attribute solutions changes to any one of the two changes made in the settings. Within GEKO, the user can make changes step by step and observe their impact on the solution separately, as all options are (or will be made) available within this model framework.

It is to be emphasized that users do not have to adjust coefficients. There are strong default settings (similar to the SST model) and there are further recommendations for settings to mimic other existing models like . It is however assumed that many simulation results can significantly be improved by very few changes to the GEKO coefficients. For simple geometries, a global optimization of the coefficients is typically sufficient. For more complex application, where several different turbulence-related phenomena are included in one set-up, the coefficients can be set via UDFs zonally. In the longer run, it can also be anticipated that the free coefficients can be used for automatic optimization and Machine Learning.