The important effects of rotation and compressibility on rotor blade boundary layers are theoretically investigated. The calculations are based on the momentum integral method and results from calculations of a transonic compressor rotor are presented. Influence of rotation is shown by comparing the incompressible rotating flow with the stationary one. Influence of compressibility is shown by comparing the compressible rotating flow with the incompressible rotating one.

Two computer codes for three-dimensional laminar respectively turbulent boundary layers, originally developed by SSPA Maritime Consulting AB, have been further developed by introducing rotation and compressibility terms in the boundary layer equations. The effect of rotation and compressibility on the transition have been studied. The Coriolis and Centrifugal forces which contribute to the development of the boundary layers and influence its behaviour, generate crosswise flow inside the blade boundary layers, the magnitude of which depends upon the angular velocity of the rotor and the rotor geometry.

The calculations show the influence of rotation and compressibility on the boundary layer parameters. Momentum thickness and shape factor increase with increasing rotation and decrease when compressible flow is taken into account. For skin friction such effects has inverse influences. The different boundary layer parameters behave similarly on suction and pressure side with the exception of the cross-flow angle, the cross-wise momentun thickness and the skin friction factor.

The codes use a nearly orthogonal streamline coordinate system, which is fixed to the blade surface and rotates with the blade.

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