Newton's Law of Viscosity

  1. What does it mean by momentum transfer is not a vector (3 components) but rather a tensor (9 components)?
     
  2. jcsd
  3. siddharth

    siddharth 1,197
    Homework Helper
    Gold Member

    "momentum transfer"? Can you elaborate?
     
  4. FredGarvin

    FredGarvin 5,087
    Science Advisor

    Newton says that viscosity is due to molecular diffusion between layers in the fluid. A molecule leaves one layer and transfers it's momentum to the adjoining layer. That transfer creates an acceleration and that acceleration creates shear forces which is related to the viscosity.

    Stresses in the most basic forms, i.e. no simplifying assumptions, are tensors. There are nine components 3 normal stresses and 6 shear stresses (note that for equillibrium, the 6 shear stresses are 2 groups of 3 that are equal, [tex]\tau_{xy} = \tau_{yx}[/tex]).

    You might like to read up on tensors by taking a look at this thread that Astronuc created in the tutorial section:
    https://www.physicsforums.com/showthread.php?t=101414
     
    Last edited: Dec 30, 2006
  5. berkeman

    Staff: Mentor

    Thanks for the link to the tutorial, Fred. Cool stuff.

     
  6. thank you very much!
     
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