Viscous Flow in a Controlled Diffusion Compressor Cascade With Increasing Incidence

A detailed two-component LDV mapping of the flow through a controlled diffusion compressor cascade at low Mach number (∼0.25) and Reynolds number of about 7×10⁵, at three inlet air angles from design to near stall, is reported. It was found that the suction side boundary layer reattached turbulent after a laminar separation bubble, and remained attached to the trailing edge even at the highest incidence, at which losses were 3 to 4 times the minimum value for the geometry. Boundary layer thickness increased to fill 20% of the blade passage at the highest incidence. Results for pressure-side boundary layer and near wake are also summarized. Information sufficient to allow preliminary assessment of viscous codes is tabulated.