Efficient Determination of Turbomachinery Blade Aero-Damping Curves for Flutter Assessment via Trigonometric Interpolation

Abstract

Proposed in the paper is a trigonometric interpolation method for efficient determination of turbomachinery blade aero-damping curves which are required in a flutter assessment. The trigonometric interpolation method was proposed to be incorporated with the widely used travelling wave method to replace the influence coefficient method. Through analyzing aero-damping/worksum at a few carefully chosen nodal diameters, trigonometric interpolation was applied through existing data points to get aero-damping/worksum at the rest nodal diameters. The proposed approach is much more efficient than the travelling wave method for determining the aero-damping curve of a blade. In principle, the method can be as efficient as the influence coefficient method. Unlike the influence coefficient method, the trigonometric interpolation method does not involve linear superposition, and it can include nonlinear effect and is expected to be more accurate. Two test cases were provided to validate the proposed method and demonstrate its effectiveness. The method is not only effective, but also very easy to be incorporated into existing widely used aero-damping/worksum analysis system using the travelling wave method.