Three-dimensional Boundary Layer Flow on Rotating Blades

In order to determine the flow characteristics of the laminar and the turbulent boundary layers on rotating blades of an axial-flow turbomachine, a theoretical analysis was performed taking the chord-wise pressure gradient into account with the aid of the rotating helical coordinates. Comparison of the calculated results of rotating blades with those of two-dimensional stationary ones showed that the secondary flow induced over the rotating blades has strong effect of suppressing the boundary layer growth, which results in that the transition and the separation of the boundary layer are much delayed. This effect increases with an increase of attack angle. To prove the validity of the theory, measurements were performed with an axial blower equipment. The measured results showed that the present analysis is well applicable to the estimation of the flow characteristics of the boundary layers on relatively thin and small-cambered rotating blades to the chord length.