# Formula - Oil-film thickness - Hydrodynamic bearings

Q.  Which of the following formula is used to calculate oil-film thickness in hydrodynamic bearings?
- Published on 19 Oct 15

a. h = (c + Є cos θ)
b. h =(c – Є cos θ)
c. h = c (1+ Є sin θ)
d. h = c (1+ Є cos θ)

ANSWER: h = c (1+ Є cos θ)

#### Discussion

• Sravanthi   -Posted on 05 Oct 15
• Oil-film thickness in hydrodynamic bearings is calculated using the formula h = c (1+ ∈ cos θ)
where,
θ = angle measured from the position of maximum oil-film thickness
∈ = eccentricity ratio

• If more viscous fluids are used film thickness at the point of minimum clearance increases.

• As speed of bearing increases the thickness of film increases for a given load and fluid.

• Hydrodynamic lubrication is also called as thick film, fluid film or flooded lubrication.

• Hydrodynamic lubrication in bearings requires thin, converging liquid or gaseous fluid films. This type of lubrication is obtained if two mating surfaces are separated completely by a cohesive film of lubricant

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