A DIGITAL TWIN OF COMPRESSOR BLISK MANUFACTURING GEOMETRICAL VARIABILITY FOR THE AEROELASTIC UNCERTAINTY QUANTIFICATION OF THE AERODYNAMIC DAMPING

This study is centered on the aeroelastic problem for axial compressors blisk airfoils in presence of geometrical variability. The combined problem of structural dynamics and unsteady aerodynamics is of interest for these machines due to the stress induced by blade vibration. The geometrical variability resulting from the manufacturing process of blisk airfoils and its impact on the aeroelastic problem is investigated, focusing on the aerodynamic damping. The manufacturing geometrical variability is analyzed in a probabilistic manner. A digital twin of the variability is created starting from a dataset of optical surface scans. The measured geometries are parameterized to describe the differences from the nominal geometry. An Autoencoder represents these deviations within a required accuracy, while using a minimal set of variables. The data reduction provided by the Autoencoder technique proved to be very efficient, especially if compared to linear methods as the principal components analysis, allowing to investigate multi-passage deviations from the nominal geometry. The aerodynamic damping is computed by an unsteady CFD solver, using the aerodynamic influence coefficients method. The manufacturing geometrical variability model is used to represent the real blisk airfoil geometries investigated. The uncertainty quantification evaluates the impact of the deviations from the nominal cyclic symmetrical design on the aerodynamic damping curve. The results can be combined in an aeroelastic reduced order model with the mistuning of the mechanical properties to represent the mistuned blisk vibrations.