Abstract
Tip leakage flows are important in compressors because of their
strong influence on cascade performance and stability. Since there
are separations and three-dimensional shear layers in tip leakage
flows, the validity of RANS is not self-evident. The objective of
this paper is to evaluate the influence of a RANS turbulence model
in tip leakage flows. To achieve this, both fully resolved LES
and RANS are conducted under the same design conditions and
Reynolds stresses and flow structures are directly compared using
the resolved LES as the high-fidelity reference result. Elicited results
indicate that RANS can reproduce the bulk exit flow angle
and Reynolds stresses distribution in a qualitative manner. However,
quantitative comparision showed that the RANS underestimate
Reynolds stresses at strong shear layers, so there are differences
in the exit total pressure loss and the velocity distribution of
the tip leakage vortex that may affect its prediction of the vortex
breakdown and rotor stall performance in the case of simulations
near the stall point.
