Efficient Unsteady Simulations of Cooled Turbines using Harmonic Balance

Efficient unsteady simulations of cooled turbines are essential for improving thermal load predictions and optimising turbine design. This study introduces a combined approach of the Harmonic Balance method, a differential Reynolds stress model, and a localised film cooling model, which captures the dominant unsteady effects in high-pressure turbine rotors. Traditional steady-state RANS simulations often under- or over-predict adiabatic wall temperatures and heat transfer coefficients due to the neglect of unsteady interactions. Results show that unsteady effects significantly impact thermal loads, with frequency-domain harmonic balance simulations closely matching high-fidelity time-domain URANS results at a fraction of the computational expense. The localised film cooling model improves accuracy over a coarser volume source model, while the SSG/LRR-log(w) turbulence model enhances turbulent mixing predictions. This can enable a much better capturing of relevant unsteady effects and turbulent mixing processes in both problem analysis and design, the impact of which would remain unknown using simpler methods.