What is the normal viscous force(stress)?

  1. Hello,

    I understand the tangential shear stresses (or forces) acting on a fluid element due to friction between moving fluid layers, but I can't imagine how viscosity might cause a normal force (on a fluid element)....explain please!
  2. jcsd
  3. boneh3ad

    boneh3ad 1,764
    Science Advisor
    Gold Member

    Who ever said that it did? Viscosity can only cause normal stresses in a compressible flow where the divergence of the velocity field is nonzero. This is, however, bulk viscosity rather than the typical dynamic viscosity.
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