Experimental Methods and Results in Unsteady Aerodynamics and Aeroelasticity

Abstract

In spite of the great progress in the field of computational fluid dynamics in the last decade, experimental research is still a major development tool in the design process of modern turbomachines. There are a number of different over-all objectives, which include the analysis of data to validate and calibrate advanced numerical calculation schemes, the improvement of the physical understanding of the flow phenomena, and investigations of new concepts to direct theoretical approaches modelling the flow effects.

The unsteady flow in turbomachines is of renewed interest. The traditional working fields on unsteady flows are concerned with the investigation of the aerodynamic stability of machines, the aeroelastic stability of cascade and single stage flows, the noise generation, and the influence of unsteady effects on the effiency. Advances in the experimental methods enabled the experimentalists to investigate the time-dependent, three-dimensional flow in turbomachine stages. A large number of experimental results in this field was published, which underline the necessity to include the unsteady effects in the design process to achieve further improvements of machine performance and reliability.

In this paper, the state of the art concerning unsteady measurements in a turbomachine environment is reviewed. Different techniques as LDV and L2F systems, tracer methods, hot-wire anemometry and subminiature pressure transducers are presented emphasis given to the dominating problems of stator-rotor interaction. An attempt is made to give an overview of the applicability, accuracy and specific limitations of the methods. Special emphasis is laid on the discussion of future needs and development directions.