Unsteady, two- and three-dimensional, thin-layer Navier-Stokes codes (STAGE-2 and STAGE-3) have been developed to study rotor-stator interaction in multistage turbomachinery. The codes use systems of patched and overlaid grids that move relative to each other to simulate the motion of the rotor airfoils with respect to the stator airfoils. An implicit, upwind-biased, spatially third-order-accurate method is used to compute the flow in each of the zones. The codes were used to simulate subsonic flow within a multistage compressor and single-stage turbine configurations and the numerical results were compared with experimental data. The agreement was found to be good for time-averaged surface pressure data and wake profiles. The presence of strong viscous interactions was demonstrated by the use of entropy contours.
The flow within the latter stages of a multistage turbomachine is much more complicated than within the first stage, indicating that it is important to simulate the flow within a multistage turbomachine using a multistage code in order to accurately estimate the time variance of the flow field. It would be extremely difficult to implement boundary conditions at the inlet of a cascade calculation that would simulate the temporally and spatially varying flows generated by upstream stages of airfoils. With smaller axial gaps between the rotors and stators of modern engines, it is anticipated that the interactions will be generally stronger and the unsteady forces much larger than those for the turbomachines studied here.