Analyse modale opérationnelle en présence d'excitations harmoniques : étude de cas sur des composantes de turbine hydroélectrique

The prediction of modal properties is essential to understand and predict the dynamic behavior of structures. In order to correlate with analytical and numerical tools, experimental validation methods need to be developed. With the collaboration of GE Energy, the use of Operational Modal Analysis to identify modal parameters directly from field test data has been investigated. The Natural Excitation Technique (NExT) using Least Square Complex Exponential (LSCE) method has been tested on the field test data from the stay vanes of a hydroelectric turbine. This paper contains the theoretical overview of the LSCE method and a modified version that allows taking into account harmonic excitations. Furthermore, an analysis of the effect of harmonic excitation using simulated data, the results from the in situ data and a comparison with analytical predictions are exposed.