What is the normal viscous force(stress)?

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SUMMARY

The discussion clarifies that viscosity can indeed cause normal stresses in fluid elements, but only in compressible flow scenarios where the divergence of the velocity field is nonzero. This phenomenon is attributed to bulk viscosity, which differs from the conventional dynamic viscosity associated with tangential shear stresses. Understanding this distinction is crucial for accurately analyzing fluid behavior in various flow conditions.

PREREQUISITES
  • Understanding of fluid mechanics principles
  • Familiarity with shear stress and normal stress concepts
  • Knowledge of compressible flow dynamics
  • Basic grasp of viscosity types, including dynamic and bulk viscosity
NEXT STEPS
  • Research the principles of compressible flow in fluid dynamics
  • Study the effects of bulk viscosity on fluid behavior
  • Explore mathematical models for shear and normal stresses in fluids
  • Learn about the divergence of velocity fields in fluid mechanics
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Fluid mechanics students, engineers working with fluid dynamics, and researchers focusing on viscosity effects in compressible flows will benefit from this discussion.

Makveger
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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!
 
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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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