TIME DOMAIN FLUTTER ANALYSIS OF CASCADES USING A FULL-POTENTIAL SOLVER

A time domain approach is used to determine the aeroelastic stability of a cascade of blades. The structural model for each blade is a typical section with two degrees of freedom. The aerodynamic model is unsteady, two-dimensional, full-potential flow through the cascade of airfoils. The unsteady equations of motion for the structure and the fluid are integrated simultaneously in time starting with a steady flowfield and a small initial disturbance applied to the airfoils. Each blade is allowed to move independently, and the motion of all blades is analyzed to determine the aeroelastic stability of the cascade. The airfoil section and structural parameters are selected to be representative of a propfan. The results are compared with those from a separate frequency domain analysis based on the same aerodynamic model. Good agreement between the results is observed. Since the present calculations are meant to validate the time domain approach, only linear examples are considered. However, with the time domain approach, it is possible to consider nonlinear structural models and nonlinear force-displacement relations. Because of this, the method allows a more realistic simulation of the motion of the fluid and the cascade blades that should lead to a better physical understanding.