Investigation of the Laminar Separation-Induced Transition With the γ-Re~θt Transition Model on Low-Pressure Turbine Rotor Blades at Steady Conditions

Abstract

The present study focuses on the assessment and the validation of the Langtry and Menter γ-Re~θt correlation-based transition model, recently implemented in the RANS code elsA from ONERA. The test cases are two Low-Pressure Turbine (LPT) rotor blades, with the same compressible Zweifel loading coefficient but different load distributions. The corresponding experimental results are provided by the von Karman Institute. The outlet isentropic Reynolds number, based on blade chord and outlet isentropic velocity, ranges from 60000 to 250000 in order to investigate the complex separation-induced transition phenomenon occurring at low Reynolds number cruise condition. The turbulence intensity is the natural freestream turbulence of the facility (0.9%). The numerical test campaign gives good predictions, particularly when accurately tailoring the trailing edge and wake regions of the mesh. The numerical mass-averaged kinetic losses are in good agreement with the experimental ones. Moreover, the flow topology parameters (the transition onset, the transition end and the separation) show good agreement in comparison to the experimental results and correlations from the open literature. One is even able to detect separation-induced transition with reattachment before the trailing edge at the lowest Reynolds number. However, the authors stress the turbulence Reynolds number effect on the prediction of separation-induced transition for strong diffusion LPT blades and particularly when the flow is subjected to a long bubble or even an open separation.