Comparative Study of Coupled-Mode Flutter-Analysis Methods for Fan Configurations

A comparative computational study of current flutter-analysis methods, for fan geometry in subsonic flow, is carried out to evaluate the relative advantage of the methods. The flutter characteristics are computed using the following three methods: time domain, work per cycle, and eigenvalue analysis. The eigenvalue analysis is based on a pulse method in combination with the influence coefficient method. The aeroelastic analyses are performed using a time-accurate solver based on Euler equations. The aeroelastic characteristics of the fan are obtained by coupling the unsteady Euler equation solution with a normal-mode analysis of elastic blades. For the coupled-mode flutter analyzed, the time-domain method indicated stability or instability faster than the eigenvalue method, whereas the work-per-cycle method failed to predict the flutter. The eigenvalue method provided the results in the form of aerodynamic damping and flutter frequency for each interblade phase angle analyzed. However, it was more expensive than the time-domain method and was better suited for analysis with a fewer number of modes. (Author)