Unsteady Flow in Turbomachines: Where’s the Beef?

Abstract Selected examples of unsteady flow in turbomachines are discussed from the point of view of their impact on aeroengine design. This vantage point serves as a focus for assessment of the “importance” of various unsteady flow processes. It is shown that for some of these processes there are clear causal links between unsteady phenomena and so-called steady-state performance measures. For others, however, the links, as well as the overall impact, are still to be established. Suggestions are given for areas in which research on unsteady flow can have a significant influence on design procedures as well as for ways in which to better define the topics that are most fruitful to pursue.