Unsteady oil film forces in porous bearings: analysis of  permeability effect on the rotor linear stability

The film forces in porous journal bearings are capable of sustaining self-exciting oscillations under certain operating conditions; if their amplitude becomes too large, it may endanger safe operation. Thus, there is a need to understand the dynamic characteristics of porous journal bearings identifying the dominant parameters.This paper aims to identify the journal stability threshold by using an original approximate analytical approach for the non-steady fluid film force and the stiffness and damping coefficients description in the case of low loaded porous journal bearings.