Susumu Ishii

Torsional flutter of stalled and unstalled mistuned cascades : Effect of natural frequency and blade arrangement on mistuning flutter

A comparison of mistuning effects on the torsional flutter suppression between fully stalled and unstalled cascades is made focusing on variation of the natural frequency and blade arrangement. Numerical results are obtained for fundamental characteristics of flutter suppression effects. In both stalled and unstalled cascades, the larger the variation of natural frequency the more stable the cascades. Furthermore, the difference in flutter modes caused by mistuning between both cascades is clarified.

Unsteady Aerodynamic Characteristics of a Blade in Pitching Oscillation with Flow Separation : 3rd Report.: The Case near the Stalling Angle of Attack

Unsteady stall characteristics of a blade oscillating in pitch at an angle of attack near stall region are examined including a dynamic hysteresis phenomenon of stalling in the process of changing the reduced frequency. Effects of this dynamic hysteresis phenomenon on unsteady aerodynamic characteristics of an oscillating blade are made clear in a region where either state of a fully separated flow or an attached (strictly speaking, partially separated) flow persists continuously during the blade oscillation depending upon the history of frequency variation. It is also found that the characteristics of aerodynamic damping are affected remarkably by the dynamic hysteresis phenomenon depending upon the location of pitching center.