Center for Turbulence Research, Proceedings of the Summer Program, 1998. pp. 267-286
Recent LES suggested that the turbulence fluctuation in the wall-normal direction v2 – f plays an important role in the evolution of transition. This motivates the use of v2 − f model for turbomachinery flows, in which different types of transition co-exist. An `ad hoc' Reynolds-number-dependent term is added to C e1 in the E-equation in order to reduce the level of near-wall dissipation rate. As a result, the onset and length of transition are greatly improved for a moderate level of free-stream turbulence intensity. However, the peak of stream wise turbulence intensity within the transition zone is underestimated. The implication of this is that the intermittency effect needs to be incorporated into the model - for example, based on the `conditioned Navier-Stokes equation' which splits the equation into turbulent and nonturbulent parts - in order to capture the correct physical mechanism of transition. Another objective of this study is to resolve the issue of whether the `elliptic relaxation' model can be used for supersonic flows. The results for the RAE2822 transonic airfoil will demonstrate that a good agreement with experimental data has been achieved. This is because the pressure-strain term (~ f), though elliptic in nature, acts simply as a source term in the v2-equation, which is not associated with the convection process.
