A STUDY ON UNSTEADY AERODYNAMIC CHARACTERISTICS OF OSCILLATING CASCADES WITH ARBITRARY BLADE PROFILES (2-DIMENSIONAL CASCADES OSCILLATING WITH BLADE SECTION DEFORMATION)

Aerodymamic characteristics of oscillating cascades of blades accompan ied by elastic deformation of blade sections in a uniform incompressib le flow are predicted numerically. Unsteady formulation is based on a small perturbation approach with the use of potential equations expres sed on a moving computational grid. The governing equations are discre tized by the finite element method. Modal shapes of blade oscillation are obtained first and a parametric study on unsteady aerodynamic char acteristics is conducted for the two-dimensional cascade of the tip se ction of a test compressor. Furthermore, the oscillation displacement of the blades is divided into four components, i.e., two translational components (normal and tangential to the blade chord), a rotational c omponent, and a section-deformation component, in order to analyze the contribution of each component to unsteady aerodynamic work which cau ses flutter excitation. It is shown that the effect of the blade secti on deformation is very significant in determining the unsteady charact eristics of oscillating cascades.