Study of the unsteady interaction between turbine rows using linear and non-linear RANS methods

In turbomachinery, the aerodynamic interaction between adjacent rows is one of the main sources of vibration. Very often, the associated synchronous response has a major impact on the high cycle fatigue behavior of the rows. In this article, the aerodynamic interaction between an NGV and a rotor stage of a representative intermediate pressure turbine are studied using different frequency-domain URANS CFD approaches, including several variations of linear and non-linear methods. The relative impact of the different mechanisms of interaction (acoustics, wakes, secondary flows) is evaluated in detail, including indirect mechanisms such as the acoustic reflections between rows. Furthermore, the importance of some aspects of the simulation set-up, such as the inclusions of additional rows in the simulation, or the use of non-reflecting boundary conditions, are explored in detail.