A CFD Based Throughflow Method with Three-Dimensional Flow Features Modelling

The paper describes the development and validation of a novel CFD-based throughflow model. It is based on the axisymmetric Euler equations with tangential blockage and body forces and inherits its numerical scheme from a state-of-the-art CFD solver (TRAF code). Secondary and tip leakage flow features are modelled in terms of Lamb-Oseen vortices and a body force field. Source and sink terms in the governing equations are employed to model tip leakage flow effects. A realistic distribution of entropy in the meridional and spanwise directions is proposed in order to compute dissipative forces on the basis of a distributed loss model. The applications are mainly focused on turbine configurations. First a validation of the secondary flow modelling is carried out by analyzing a linear cascade based on the T106 blade section. Then the throughflow procedure is used to analyze the transonic CT3 turbine stage studied in the framework of the TATEF2 European program. The performance of the method are evaluated by comparing predicted operating characteristics and spanwise distributions of flow quantities with experimental data.