Flutter Stability of a Transonic Compressor Rotor - Application and Comparison of Different Numerical Methods

Abstract

This paper investigates the flutter mechanism of a high loaded transonic compressor rotor by applying different numerical methods. For predictions of the stability in the frequency domain, harmonic fluid forces are calculated with a linearized Euler method and with a nonlinear time domain Navier-Stokes solver for forced motion. To include nonlinear effects in the stability prediction, the time domain method is applied in a fluid-structure coupled mode of operation. The results of this 3D viscous aeroelastic computations in the time domain for the whole annulus of the rotor are compared to the frequency domain solutions. The comparative study shows that shock-boundary layer interactions significantly influence the stability of the compressor rotor. While for higher reduced frequencies the rotor still behaves linearly, for lower reduced frequencies limit cycle oscillations (LCO) due to shock-boundary layer and shock-shock interaction occur.