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To assign non-winter grades, kinematic viscosity is graded by ASTM D445 or ASTM D7042, measuring the time it takes for a standard amount of oil at a temperature of 100 °C (212 °F) to flow through a standard orifice, in units of mm 2 /s (millimetre squared per second) or the equivalent older non-SI units, centistokes (abbreviated cSt). The ...
The Vogel–Fulcher–Tammann equation, also known as Vogel–Fulcher–Tammann–Hesse equation or Vogel–Fulcher equation (abbreviated: VFT equation), is used to describe the viscosity of liquids as a function of temperature, and especially its strongly temperature dependent variation in the supercooled regime, upon approaching the glass transition.
The Saybolt universal viscosity test occurs at 100 °F (38 °C), or more recently, 40 °C (104 °F). The Saybolt FUROL viscosity test occurs at 120 °F (49 °C), or more recently, 50 °C (122 °F), and uses a larger calibrated tube. This provides for the testing of more viscous fluids, with the result being approximately 1 ⁄ 10 of the ...
Extensional viscosity can be measured with various rheometers that apply extensional stress. Volume viscosity can be measured with an acoustic rheometer. Apparent viscosity is a calculation derived from tests performed on drilling fluid used in oil or gas well development. These calculations and tests help engineers develop and maintain the ...
where U is the oil's kinematic viscosity at 40 °C (104 °F), Y is the oil's kinematic viscosity at 100 °C (212 °F), and L and H are the viscosities at 40 °C for two hypothetical oils of VI 0 and 100 respectively, having the same viscosity at 100 °C as the oil whose VI we are trying to determine.
In fluid mechanics (specifically lubrication theory), the Reynolds equation is a partial differential equation governing the pressure distribution of thin viscous fluid films. It was first derived by Osborne Reynolds in 1886. [ 1 ]
More dramatically, a long-chain hydrocarbon like squalene (C 30 H 62) has a viscosity an order of magnitude larger than the shorter n-alkanes (roughly 31 mPa·s at 25 °C). This is also the reason oils tend to be highly viscous, since they are usually composed of long-chain hydrocarbons.
c is the radial clearance μ is the absolute viscosity of the lubricant N is the speed of the rotating shaft in rev/s P is the load per unit of projected bearing area. The second part of the equation is seen to be the Hersey number. However, an alternative definition for S is used in some texts based on angular velocity: [2]