Turbulent Transition Model Validation with Multiple Rotors for Industry Application

The Langtry-Mentor transition model with k-w Shear Stress Transport (SST) model has been assessed for multiple rotors. In this assessment, an adverse impact of the sustaining term has been identified and a modification has been introduced. It was found that the original sustaining term behaved poorly for the separated flows investigated herein, making separation worse and leading to a premature stall in hover. The modified sustaining term uses F1-μ_t blending to deactivate the sustaining term inside boundary layer. The Langtry-Mentor transition model with the modified sustaining term has been validated for multiple rotors with various scales and characteristics, including the XV-15 rotor, the Hover Validation and Acoustic Baseline (HVAB) rotor, and Sikorsky’s model- and full-scale rotors. Helios, with OVERFLOW as near-body solver, was used for these calculations. The validation showed very good correlation with measured hover figure of merit data for all rotors from low thrust to high thrust conditions, using a consistent transition model and sustaining-term settings. It was found that the modified sustaining term removed the adverse impact of the original sustaining term.