The Effects of Turbulence Length Scale on Turbulence and Transition Prediction in Turbomachinery Flows

Abstract

An approach for estimation of the turbulence length scale at the inflow boundary is proposed and presented. This estimation yields reasonable turbulence decay, supporting the transition model in accurately predicting the laminar-turbulent transition location and development. As an additional element of the approach, the sensitivity of the turbulence model to free-stream values is suppressed by limiting the eddy viscosity in non-viscous regions. Therefore the well known realizability constraint after Durbin [1] is modified. The method is implemented in DLR’s turbomachinery flow solver TRACE in the framework of the k–ω turbulence model by Wilcox [2] and the γ–Reθ transition model by Langtry and Menter [3]. The improved model is tested to the T106A turbine testcase and validated at the T161 turbine cascade under low speed conditions and T170 turbine cascade at high speed conditions.