Überschusswendung

Überschusswendung is a German term that translates to "surplus turning" or "excess turning." It describes a concept primarily found in the field of fluid dynamics and engineering, particularly in relation to rotating machinery like turbines and pumps. The term refers to the phenomenon where the fluid entering a rotating component, such as a turbine impeller or a pump volute, possesses a tangential velocity component that is in the same direction as the rotation of the component. This is in contrast to a "deficiency turning" or "negative turning" where the fluid's tangential velocity opposes the rotation.

In the context of turbomachinery design, achieving a controlled Überschusswendung can be beneficial for optimizing energy transfer and efficiency. For instance, in certain pump designs, a specific degree of incoming fluid swirl in the direction of impeller rotation can lead to improved flow stability and reduced recirculation losses. Conversely, an uncontrolled or excessive Überschusswendung can sometimes indicate inefficient upstream flow conditions or can negatively impact the performance of downstream components. Engineers analyze and design for specific levels of Überschusswendung to achieve desired operational characteristics, such as maximizing head in a pump or torque in a turbine. The presence and magnitude of Überschusswendung are often determined through computational fluid dynamics (CFD) simulations and experimental measurements.