fluid bearings

are bearings which solely support the bearing's loads on a thin layer of liquid or gas.  They are typically classified as either "fluid dynamic bearings", "hydrostatic" or "gas bearings" also known as a foil bearing. They are frequently used in high load, high speed or high precision applications where ordinary ball bearings have short life or high noise and vibration. They are also used increasingly to reduce cost. For example, hard disk drive motor fluid bearings are both quieter and cheaper than the ball bearings they replace.  Fluid bearings use a thin layer of liquid or gas fluid between the bearing faces, typically sealed around or under the rotating shaft.  There are two principal ways of getting the fluid in to the bearing:

A.  gas bearings and hydrostatic bearings, the fluid is pumped in through an orifice or through a porous material.

B.   hydrodynamic bearings, bearing rotation sweeps the fluid in to the bearing, forming a lubricating wedge under or around the shaft.

Also see foil bearing.