ABSTRACT
In turbomachinery, there are stationary and moving blades making relative movements in a confined area. The flows are surrounded by blades, casing, and hub. Along these surfaces, there are boundary layers. If the axial distances are small, interference effects arise between moving and stationary blade rows. The causes of these effects are potential flow effects and wake effects arising from upstream blades. If the axial distances are not very small, the potential effect disappears, and the wake effects become the main causes of unsteady flow. Besides, if there are tip clearances between casing and tip of the blade, then the pressure difference between the pressure and the suction side of the blade causes leakage of flow, which causes unsteady flow. The flow phenomena are different with different flow Reynolds numbers, i.e., rotational speed and operating conditions.
