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Why are materials viscous?

  1. May 7, 2018 #1
    As I understand, viscosity characterizes the "resistance" of a material to "flow locally" as a function of the velocity of the material flow.
    Now my question is following, what are the physical mechanisms involved which make this "resistance" dependent on velocity of the material movement/flow?
    If the atomic interactions are a function of positions/displacement of atoms/material points... Where is this velocity dependence comming from??
  2. jcsd
  3. May 7, 2018 #2
    It is not dependent on the velocity. It is dependent on the spatial velocity gradient. To get an understanding of how the atomic interactions come into play, see Chapter 1 of Transport Phenomena by Bird, Stewart, and Lightfoot.
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