Numerical Prediction of the Heat Loads on a Turbine Vane Test Case

The numerical evaluation of the external heat transfer coefficient distribution over a turbine vane surface is a mandatory task in the view of designing reliable and thermally efficient cooled components. Despite having been investigated for a long time, this prediction is still a challenging one, especially when test cases with non negligible free-stream turbulence and potential boundary layer transition are tested. The present work shows the results of a numerical investigation performed on the VKI LS 89 profile in a linear cascade. The numerical results were compared against an experimental database achieved on a 1 vane 2 passages linear cascade rig, hosting the LS89 profile, with the possibility to reach a high free stream turbulence intensity up to 15%; a low (natural) turbulence condition was also tested for comparison. Attention was paid to assess the capabilities of RANS approaches, with a systematic analysis aimed and comparing the performance of different solvers and transition models, as well as to highlight the impact of aspects like the type of computational grid and the choice of the turbulent Prandtl number. Attention was also put in comparing the outcome achieved from different solvers, a commercial and an academic one, so to critically assess their capabilities.

Moreover, a scale resolved LES simulation was carried out, in order to provide a numerical benchmark and understand the limitations of the turbulence modeling. While the low turbulence test point could be replicated with a sufficient accuracy by all the considered methods, as also pointed out by previous literature studies, none of the RANS considered settings could provide a completely satisfactory matching for the high turbulence case. Still, a far superior behaviour was retrieved by the academic code, equipped with a specifically developed transition model. The data shown in the current work represents a useful validation of numerical approaches that can be generally adopted for industrial applications, on the challenging environment of the well known LS89 profile, tested at a higher and more engine representative turbulence condition.