Transition Modeling for General CFD Applications in Aeronautics

A new correlation-based transition model has been developed, which is built strictly on local variables. As a result, the transition model is compatible with modern CFD techniques such as unstructured grids and massively parallel execution. The model is based on two transport equations, one for intermittency and one for a transition onset criterion in terms of momentum thickness Reynolds number. The proposed transport equations do not attempt to model the physics of the transition process (unlike e.g. turbulence models), but form a framework for the implementation of transition correlations into general-purpose CFD methods. The transition model was initially developed for turbomachinery flows. The main goal of the present paper is to validate the model for predicting transition in aeronautical flows. An incremental approach was used to validate the model, first on 2D airfoils and then on progressively more complicated test cases such as a 3-element flap, a 3D transonic wing and a full helicopter configuration. In all cases good agreement with the available experimental data was observed. The authors believe that the current formulation is a significant step forward in engineering transition modeling, as it allows the combination of transition correlations with general purpose CFD codes. There is a strong potential that the model will allow the 1 st order effects of transition to be included in everyday industrial CFD simulations.