The Use of a Turbulence Weighting Factor to Model By-Pass Transition

Abstract

To simulate transitional heat transfer in turbine cascades, the conditionally averaged Navier-Stokes equations are used. To cover both the physics of free-stream turbulence and the intermittent flow behavior during transition, a turbulence-weighting factor is used. A transport equation is presented for this factor including convection, diffusion, and production, and sink terms. In combination with the conditioned Navier-Stokes equations, the transport equation leads to improvements in the calculation of flow characteristics in both the transitional layer and the free-stream. The method is validated on transitional heat transfer measurements in a linear turbine cascade at typical operational conditions. The numerically obtained results are in good correspondence with the experimental data. Besides pressure gradient and turbulence level, the effect of compressibility needs to be considered to assure the correct prediction of both the transition onset and length..