Prediction of By-Pass Transition by Means of a Turbulence Weighting Factor: Part I — Theory and Validation

Abstract

The classical intermittency factor γ for quantifying transition is redefined and extended to enable the modelling of by-pass transition. Therefore, a new parameter, the turbulence weighting factor τ, is introduced to cover both the physics of freestream turbulence diffusion and of turbulent spots. A transport equation is presented for the τ-factor including convective, diffusive, production and sink terms. In combination with the conditioned Navier-Stokes equations, this leads to improvements in the calculation of flow characteristics in both the transitional layer and the freestream.