Abstract
In previous studies, the pressure recovery of highly-loaded annular
diffusers was identified to correlate with the Reynolds shear
stresses at rotor outlet in the blade tip region. The origin and propagation
of the Reynolds shear stresses, however, have not been experimentally
clarified yet due to measurement probe constraints. Hence
in the present work, the origin of these stresses, as well as the transport
throughout the flow channel is analyzed by simulating the rotor
with the scale adaptive turbulence model SAS-SST is used. Using
the SAS approach, the Reynolds shear stress characteristics of the
simulation are validated by the experimental results, whereas common
RANS approaches are shown not to be appropriate. The tip
leakage vortex is found to be the source of the Reynolds shear stress
production. The interaction between vortex and mean flow leads to
turbulent momentum transport. The Reynolds shear stresses propagate
into the rotor far-field connected to the blade tip vortices which
mix about four chord lengths downstream of the rotor trailing edge.
