• What's Viscosity? wiki

  　

  The viscosity of a fluid is a measure of its resistance to deformation at a given rate.
  Viscosity can be conceptualized as quantifying the frictional force that arises between adjacent layers of fluid that are in relative motion

  　

  Newton's law of viscosity is not a fundamental law of nature, but rather a constitutive equation (like Hooke's law, Fick's law, and Ohm's law) which serves to define the viscosity μ .

  Its form is motivated by experiments which show that for a wide range of fluids, μ is independent of strain rate. Such fluids are called Newtonian. Gases, water, and many common liquids can be considered Newtonian in ordinary conditions and contexts.

Only a small group of fluids exhibit such constant viscosity. The large class of fluids whose viscosity changes with the strain rate (the relative flow velocity) are called non-Newtonian fluids. For example:

• Shear-thickening liquids, whose viscosity increases with the rate of shear strain.

• Shear-thinning liquids, whose viscosity decreases with the rate of shear strain.

• Thixotropic liquids, that become less viscous over time when shaken, agitated, or otherwise stressed.

• Rheopectic (dilatant) liquids, that become more viscous over time when shaken, agitated, or otherwise stressed.

• Bingham plastics that behave as a solid at low stresses but flow as a viscous fluid at high stresses.

Rheology generally accounts for the behavior of non-Newtonian fluids, by characterizing the minimum number of functions that are needed to relate stresses with rate of change of strain or strain rates.

　

The term rheology was coined by Eugene C. Bingham, a professor at Lafayette College, in 1920, from a suggestion by a colleague, Markus Reiner.

　

• Units of Viscosity The Engineering ToolBox hydramotion

• 學習目標

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如何使用 Thomas-Stormer viscometer

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Rheology

• 黏滯係數的測量實驗 phy_lab