Introduction to unsteady flow in turbomachines

In this lecture some of the fluid dynamic phenomena that are associated with unsteady flow in turbomachines will be examined. It will be seen that there are several different sources of this unsteadiness, and that which of these is most important will depend on which aspect of the overall performance of the turbomachine is being examined. This discussion is intended to be an introduction to the subject and to provide an appreciation for the basic fluid mechanic concepts, rather than to be an exhaustive review. The topics to be covered are: (1) the Inherent Unsteadiness of Turbomachinery Flows; (2) Sources of Flow Unsteadiness in Turbomachines; and (3) Introductory Discussion of Unsteady Viscous Flows.