Limitations in Turbomachinery CFD

Nowadays, Computational Fluid Dynamics (CFD) is a widely used method for the analysis and the design of gas turbines. The accuracy of CFD is rapidly increasing thanks to the available computational resources that allow simulating high-speed flows using hi-fidelity methodologies. However CFD uses models, and several approximations and errors derive from the process, for example from the truncation errors due to the discretization of the Navier-Stokes equations and from the turbulence models. Typical examples of such kind of limitations may be the steady flow assumption, the turbulence closure or the mesh resolution. The impact of approximations could be minimum to evaluate the trends of variation of global parameters, but it will have a strong impact on the prediction of local values of important parameters such as flow temperature and heat transfer. It is worth highlighting that the available computational resources are pushing towards the so called high fidelity CFD and it is important to highlight what is needed to achieve this goal and to reduce the impact of approximations.

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