Although the importance of periodic unsteadiness, induced by the relative movements of adjacent airfoil rows in turbomachinery, has long been

acknowledged by design engineers, the unavailability of established predic­ tion methods has precluded an explicit impact on the hardware design. The effects of periodic unsteadiness, until recently, were accounted for through empiricism in correlations and criteria used in design procedures. Applica­ tion of these procedures often yield nonoptimal designs requiring expensive and time-consuming development programs. Work has been done over the past 15 years to develop more rigorous procedures to account for these unsteady flow effects as discussed below (Sharma et al., 1994).