Early flutter warning in wind tunnel testing using Operational Modal Analysis

This paper discusses an early-warning system for flutter detection during wind tunnel testing of scaled models. In this type of testing, it is desired to carefully verify and track the vibration behavior, since during flutter appearance, model destruction may occur. To this aim, sensors are mounted on the model and the dynamic response is measured. From the analysis of the data, an assessment of flutter safety can be made. In this paper, wind tunnel data at various flow conditions are used to validate the speed and reliability of an Operational Modal Analysis approach for tracking the evolution of the eigenfrequencies, damping ratios and mode shapes of the tested component. Operational Modal Analysis allows extracting these parameters from the structural response to natural turbulence excitation without the need for special artificial excitation. Both strain gauge and acceleration data are used.