Non-laminar regime

Conventional lubrication theory assumes that inertia forces within the fluid film are negligible compared to viscosity and pressure forces; however, in a hydrodynamic bearing, these forces become predominant when operating clearances are large, kinematic viscosity is low or the linear speed of the rotating shaft is high. The presence of inertial forces in the film means that the Reynolds equation can no longer be used to calculate bearings. What's more, when inertial forces reach a certain value, they modify the structure of the flow, which gradually becomes turbulent. As the bearing's characteristic Reynolds or Taylor number increases, the Taylor vortex regime and the turbulent regime are encountered. In the case of thrust bearings, there is also a transition regime characterized by the existence of vortices, which precedes the turbulent regime.