Computation and turbulence modeling of unsteady flows due to rotor/stator interaction in turbomachines

The performance and fatigue life of turbomachines are significantly affected by the presence of unsteady flows. The objective of this research is to develop accurate and efficient computational procedures and turbulence models for the prediction of the complex unsteady flow fields and to improve the understanding of the unsteady flow mechanism resulting from rotor/stator interactions.;An assessment of the near-wall and low-Reynolds-number functions used in low-Reynolds-number k-;A three-dimensional time accurate Euler code has been developed. Three-dimensional unsteady non-reflecting inlet and outlet boundary conditions are formulated to remove the spurious numerical reflections. The unsteady Euler solver is then used to simulate the propagation of nozzle wake and secondary flow through the rotor and the resulting unsteady pressure field in an axial turbine stage. The three dimensional and time dependent propagation of nozzle wakes and secondary flow in the rotor blade row is studied.;The unsteady pressure and boundary layers on a turbomachinery blade row arising from periodic wakes due to upstream blade rows are investigated using an inviscid/viscous procedure. The unsteady Euler solver is used to capture the wake propagation and the resulting unsteady pressure field, which is then used as the input for a 2-D unsteady boundary layer procedure to predict the unsteady response of blade boundary layers. Numerical simulations are carried out to understand the effects of the wake velocity defect and the wake turbulence intensity on the development of unsteady blade boundary layers. A parametric study is also carried out to determine the influence of wake parameters on the development of the unsteady blade boundary layers.