Transient flow in infinitely thin airfoil cascade

Abstract

Pulsed flows in turbines have many industrial applications. However, the influence of pulsed flow on turbine performance is complex and imperfectly understood. There is no clear consensus in the literature regarding generic trends. Those are difficult to extract since a majority of studies are based on industrial geometries, which involve strong interactions between many physical phenomena. In order to isolate and understand the main expression of the physics, the problem is simplified and an investigation is carried out on the severe transient regime inside a thin airfoil cascade, caused by a sudden change of inlet conditions, without viscosity effect. Different time scales of the inlet perturbation are examined, from a sudden step of the flow features to a more progressive ramp. The consequences of the different regimes observed inside the flow regarding some indicators of performance are detailed. Finally, the characteristic time of the transient flow is isolated and proposed as an indicator to assess the relevance of the quasi-steady assumption.