# Towards an Extension of the V2F Model for Transitional Flows Rapport, 2006

In part, this study investigates the performance of the turbulence model of Walters & Leylek (2004) in the flow over a flat plate under the influence of a disturbed freestream. The most important feature of the model is that is solves an equation for a laminar kinetic energy, which is coupled to a typical $k-\varepsilon$ model, to improve the performance in transitional flows. The model is shown to be very sensitive to the prescribed freestream turbulence length scale. The study also describes the initial steps towards coupling the laminar kinetic energy transition modelling approach, suggested by Walters & Leylek (2004), to the V2F turbulence model in an effort to improve the V2F model's performance in transitional flow regimes. This coupling requires modifications of the $v^2-f$ model but the intention is that the new model should retain the properties of the original model in fully turbulent boundary layers and that the additional laminar kinetic energy equation should make the predictions in transitional boundary layers more reliable. Finally, in an initial numerical study some potential pitfalls when modelling the flat plate flow are analyzed. It is shown that the predicted transitional behavior obtained with the simplified, as compared with the experimental set-up, numerical domain used in this study may be directly compared with measurements.