Comparison of les and rans predictions with experimental results of the fan of a turbofan

Abstract

This paper aims at validating LES capability if applied to an actual turbofan configuration at nominal regime, if compared to RANS and experimental measurements. For assessment, averaged radial profiles are compared in 3 axial planes – before the stage, between the rotor blade and stator vanes, and downstream of the stator. RANS and LES results are in very good agreement, but found to be shifted compared to the measurements and for some quantities. An analysis of the unsteady axial velocity is then proposed, investigating root-mean square of axial velocity. Tip-leakage, as well as two boundary layer transitions are evidenced in the rotor. An estimation of the integral turbulent timescale is finally proposed in the whole domain, using autocorrelation of the axial velocity. Suction- side horseshoe vortices are found to be very coherent, as well as the stator corner vortices. Regions of large timescale are moreover evidenced between rotor and stator wakes.