Magnitude of eddy viscosity for laminar flow - Fluid Mechanics

Q.  Magnitude of eddy viscosity for laminar flow is
- Published on 05 Aug 15

a. less than zero
b. zero
c. greater than zero
d. unpredictable

ANSWER: zero
 

    Discussion

  • Pankaj   -Posted on 29 Sep 15
    The expression for turbulent shear stress is given by

    τ = η (du / dy)

    Where,
    u = Average velocity at a distance y from boundary

    and η (eta) = Turbulent coefficient of mixing is also called as eddy viscosity or apparent viscosity or virtual viscosity.

    Eddy viscosity is functional characteristics of flow but not the property of fluid. If the flow is laminar, then the value of eddy viscosity is zero and it is several thousand times of μ, if flow is turbulent.

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