Wavelet Analysis of a Blade Tip-Leakage Flow

The secondary flow generated by the clearance between an isolated airfoil tip and an end-plate is analyzed by means of a zonal large-eddy simulation, in comparison with available experimental data. The flow around the tip clearance is described with full large-eddy simulation, while Reynolds-averaged Navier-Stokes is employed in the rest of the computational domain in order to limit the computational cost. The various analyses of the flow characteristics (mean velocities, Reynolds stresses, spectra) show a very good agreement between the experiment and the simulation. Furthermore, a detailed analysis is carried out from the numerical results. The flow separations on the blade tip are related with the leakage distribution along the chord, which generates an intense tip-leakage vortex on the suction side. Finally, a hump in the pressure spectra at tip is investigated by means of a wavelet conditional average, and related to the unsteadiness of the aft tip separatio