fluidbearing

Fluid bearing is a bearing that supports one or more rotating parts by means of a thin film of a fluid that fills the clearance between bearing surfaces. The fluid provides load support, lubrication, and damping, reducing solid-to-solid contact and wear. The fluid may be a liquid lubricant such as oil or a gas, and the bearing may rely on hydrodynamic pressure, externally supplied hydrostatic pressure, or a combination of both.

Hydrodynamic bearings generate film pressure from relative motion, requiring speed to build load-carrying pressure. Hydrostatic bearings use an external pump or gas source to supply pressurized fluid, creating a film independent of velocity. Gas bearings, such as air bearings, use a pressurized gas to support the load and are common in high-speed, clean-room environments. Foil bearings use flexible foils that trap a lubricant film and separate surfaces; they are common in light- to medium-load, high-speed applications.

Fluid bearings offer very low friction, high speed capability, and excellent damping for vibration control, with reduced wear and long life when properly lubricated. They require continuous lubricant supply and controlled temperature; susceptibility to contamination and leaks can complicate sealing. They also involve more complex design and maintenance than some dry or magnetic bearings.

Common applications include precision machine-tool spindles, high-speed rotating equipment, turbine and compressor stages, and some hard disk drive platforms. Air and oil film bearings are used in aerospace gyroscopes, vacuums, and subsea equipment.

Design considerations include lubricant viscosity, film thickness, load capacity, stiffness and damping, thermal management, and sealing. Maintenance includes lubricant replenishment, contamination control, and monitoring for wear or film breakdown.