High pressure compressor do have relatively light rotor and can have asymmetric loading due to location of balance drum etc. Rotor bearing system should have high stability features. For traditional labyrinth seals used as medium pressure centrifugal compressors, radial and tangential forces depend linearly on frequency and stiffness. In those designs, damping coefficients can be identified with reasonable accuracy by a linear curve that can measure forces in radial and tangential directions.
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