View article

PREDICTIONS of unsteady turbomachinery flows due either to rotor/stator interaction or blade vibration have attracted considerable attention. Corresponding solution methods can be developed using either time-linearized models in which unsteadiness is assumed to be a small perturbation to steady flow, 1'3 or nonlinear time-marching techniques. 4'6'8 It is well recognized that nonlinear time-marching calculations, although making fewer assumptions, are much more expensive than time-linearized solutions. A typical problem for time-marching calculations for unsteady turbomachinery flows is how to implement a periodic boundary condition, if the computation is conducted in a single blade passage, as shown in Fig. 1. For blade row interaction problems, if the rotor and stator rows have different blade numbers as in all practical situations, the upper periodic boundary (ab or ef) will sense what the lower boundary …