In a turbomachine, gaps separate stator and rotor disks. For turbines, often a purge flow is blown through these gaps in order to seal and avoid hot air to penetrate deep in the turbine disk components and over-solicit them. The interaction of this purge flow with the main flow creates and amplifies vortex structures, responsible for aerodynamic losses. Accurately predicting these losses remain a challenge with RANS approach for engine manufacturers that wish to design an efficient cavity geometry minimising the losses while ensuring the sealing. The Boussinesq approximation fails in such flows where a high turbulence level and anisotropy are present. Therefore, in RANS, the use of two-equation linear eddy-viscosity turbulence models is questionable. The present work assesses a second order Reynolds Stress Model (RSM), as well as two eddy-viscosity models, in a linear turbine cascade with an upstream cavity from which a purge flow emanates. The specificity of this cascade is the high external turbulence intensity (6%), which is all the more challenging in a RANS approach. Different purge mass flows and three configurations are evaluated: two with different cavities and one without any. The RANS simulations are compared to experimental data. All the RANS models show the same trends: the presence of a cavity induces additional pressure losses; increasing the purge mass flow helps to seal the cavity entry but nourishes the passage vortex and thus leads to additional losses. The RSM simulation shows the best agreement with the measurements and is the only one that predicts the loss evolution when the cavity chute geometry changes.
KEYWORDSSubscript denoting a position at 1/4 C x downstream of the trailing edge