On the issue of solution divergence due to sub-synchronous oscillations in foil air bearing rotor systems

Foil air bearing (FAB) rotor systems are susceptible to sub-synchronous vibrations driven by self-excitation from the air film. Although current predictions of sub-synchronous vibrations have shown good correlation with experiments under lab conditions, this is typically only up to a certain speed, beyond which the size of the predicted oscillation causes solution divergence. This paper investigates the effect of introducing a journal-to-foil contact pressure function to mitigate solution divergence. For the simple rotor system considered, the solution divergence speed was raised by at least 115%, with further increases achievable with a higher resolution grid/order of the computational method.