Application of the TLVA model for predicting film cooling under rotating frames

An in-house three-dimensional Navier-Stokes code was used to evaluate the advantages of anisotropic turbulence models over the classical isotropic turbulence models for the prediction of film cooling under rotating conditions. The anisotropic turbulence model we chose was the two-layer TLVA model and the isotropic turbulence models were the standard k-ε, the k-ω and the SST models. For the purpose of validation of numerical results, a test rig was setup and experiments were carried out for film cooling under rotation. The test model had a flat test surface with a 4 mm diameter straight circular cooling hole in 30° inclined injection and it rotated at four different speeds of 0, 500, 800 and 1000 rpm. Experiments were accomplished with the momentum ratio set to be 0.285, the Reynolds number kept at 1.45 × 10⁵ and the averaged density ratio at 1.026. Comparison indicated that the TLVA anisotropic turbulence model preformed best against its isotropic counterparts and produced the closest local cooling effectiveness η to the experimental results of all conditions. Detailed flow and temperature field analysis revealed that the improvement of anisotropic turbulence model was mostly due to its ability in accurately simulating the film lateral spreading. On the contrary, the isotropic turbulence models heavily underestimated the lateral spreading of the cooling film and this led to the overshooting of cooling effectiveness along the centerline regions and the undershooting for the rest parts. Apart from the cooling effectiveness, deflection of the cooling film from centerline due to Coriolis and centrifugal forces under coordinate rotation was also best predicted by the TLVA model.