Numerical investigation of wake/shock interaction in oscillating blade row

This paper investigated numerically the influence of wake/shock interaction on the unsteady flow in oscillating blade rows.The numerical scheme chosen is an advanced harmonic method.Based on Fourier transform,turbomachinery unsteady flow variables can be decomposed into a time-averaged part and a number of harmonics identifiable by their frequencies.Thus,time-domain unsteady Navier-Stokes equations can be converted to frequency-domain steady Fourier coefficient equations.The solution of Fourier coefficient equations was obtained by using a conventional pseudo-time marching scheme.To speedup the solution convergence,local time stepping and multi-grid acceleration techniques were used.In this paper,the numerical method was used to study the unsteady flow response under wake and blade vibration interaction.The test case chosen was NASA67 Rotor oscillating a first torsion fashion.The results show an obvious influence of upstream wake on the unsteady flow in oscillating blade rows.In the presence of the upstream wake,shock in blade passages reveals considerable excursion in the axial direction and blades witness increased amplitude and temporal periodicity losing of the unsteady force.