The experimentally determined behavior of a short radial squeeze-film damper with no end seals, executing circular centered orbits, is discussed. Accurate circular orbits were achieved, for ε values in the range 0.1 and 0.8, by using digitally generated signals to drive two electromagnetic shakers. Radial and tangential dynamic fluid force coefficients were estimated from measurements of the applied forces and the orbit radii, using a simple algebraic method. Cavitation was found to occur when ε exceeded 0.5, at large orbit frequencies, and was the cause of an observed jump-up phenomenon. The magnitude of an oil stiffness effect, previously reported by the authors and confirmed by the present results, was found to depend significantly on the oil supply pressure. Its contribution to the total fluid force was of the same order as that from fluid inertia, in the case of small orbits (ε ≪ 1).

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