Some unresolved physical problems in turbomachinery flows

Even for the ostensibly two-dimensional (2D) flow through cascades of blades, much of the basic flow physics is not well understood or predicted. A principal research focus in turbomachinery flows is presently on the computation of three dimensional (3D) flows. This paper is a reminder that 2D flows are also important and their problems are also not resolved. In cascade tests on a turbine nozzle vane many flow features have been identified in the 2D flow through the blade passage that require further attention. Of the issues identified, the focus of this paper is on three of these. The chosen topics are boundary layer transition, wake interaction effects including the calmed region, and shock-boundary layer interactions. The emphasis is on continuing to understand and represent the flow physics.