Flutter characteristics of rotor blades including up-and downstream interaction were simulated by self-developed unsteady flow simulation programs. Influence of wakes and potential waves on blade aerodynamic damping were studied. Energy exchange method was used to calculate the damping values. Variation of aerodynamic damping with different axial gaps was identified by FFT transformation of unsteady pressures on rotor blade surfaces. Interaction effects on the flutter characteristics of rotor/stator and IGV/rotor configurations were assessed by comparing the damping data with that of the single rotor. The results show that the positive damping was obtained at 100% chord axial gap for IGV/rotor configuration

in contrast with the aeroelastic stability prediction of the isolated rotor. This indicates the interaction must be considered in flutter analysis. The results also illustrate that wake and potential wave effects are intensified with reducing axial gaps

and both destabilize the rotor blades.