A third-order-accurate upwind-biased Navier-Stokes zonal code (STAGE-2) has been developed to compute flows in multistage turbomachines. Systems of overlaid and patched grids are used to resolve viscous effects near airfoils allowing the rotor/stator interaction problem to be modeled. Flexible database and bookkeeping systems are used to allow flows to be computed in turbomachines with any number of stages.
Results from STAGE-2 compared well with experimental data for both surface pressures and wake profiles. Grid refinement substantially improved the agreement with experiment for the wake profiles, although static pressures were relatively insensitive to grid refinement. The temporal variation in airfoil force was 10% of the time-averaged force for the relatively large axial gaps found in this compressor. Strong viscous interactions were demonstrated by the use of entropy contours. The flow within the second stage of the compressor was highly complex, indicating the importance of unsteady-flow analysis in a multistage turbomachine.
With smaller axial gaps between the rotors and stators of modern engines, it can be anticipated that the interactions in general will be stronger and the unsteady forces in particular will be much larger than those for the compressor studied here.