The advancement in the performance of the turbomachines requires a transonic or supersonic operation and also the larger and thinner blades to increase the power per stage. The large aerodynamic forces consequently act on such blades, which increases the possibility of flutter from the view point of unsteady aerodynamics and aeroelasticity. In such a high velocity region, in the transonic flow regime especially, the shock waves complicate the aerodynamic aspects such as a mixture of subsonic and supersonic flow properties around a blade, a shock wave reflection on the neighboring blades and the interference with the boundary layer and so on. From an unsteady aerodynamic point of view, it is important that the shock wave movement along the blade surface induces a large fluctuation of aerodynamic loads due to a significant chordwise change in surface pressure across the shock wave. The shock wave thus plays an important role in the unsteady aerodynamic characteristics of transonic cascades. It is therefore important to understand the unsteady aerodynamic characteristics including the shock wave oscillation.
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