Shear stress direction and the velocity gradient

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SUMMARY

This discussion focuses on the shear stress direction and velocity gradient in laminar fluid flow, specifically within a cylindrical pipe. The shear stress is defined by the equation τ = μ(du/dy), where μ represents viscosity, du is the velocity difference, and dy is the distance between the top and bottom planes of a fluid slab. The Cauchy stress relationship is emphasized for determining stress on surfaces of arbitrary orientation, with specific attention given to the stress tensor components for a viscous Newtonian fluid. Participants are encouraged to consult resources such as "Transport Phenomena" by Bird, Stewart, and Lightfoot for deeper understanding.

PREREQUISITES
  • Understanding of laminar flow dynamics
  • Familiarity with the Cauchy stress relationship
  • Knowledge of stress tensor components for viscous fluids
  • Basic principles of fluid mechanics
NEXT STEPS
  • Study the Cauchy stress relationship in detail
  • Learn about the stress tensor for cubical and parallelepiped elements
  • Explore the derivation of shear stress in laminar flow scenarios
  • Review "Transport Phenomena" by Bird, Stewart, and Lightfoot for advanced concepts
USEFUL FOR

Fluid mechanics students, engineers working with fluid dynamics, and researchers focusing on viscous flow analysis will benefit from this discussion.

  • #31
sir but how to get the term in #19 ? and sir one more doubt If we have a cubical element how we are going to write the term #19 ? Is it going to remain the same??
 
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  • #32
Rahulx084 said:
sir but how to get the term in #19 ? and sir one more doubt If we have a cubical element how we are going to write the term #19 ? Is it going to remain the same??
The term in #19 follows from the equations for the stress tensor components for a viscous Newtonian fluid. Are you familiar with these equations?

When you have a cubical element (or rectangular parallelepiped), you use the stress tensor in component form for Cartesian coordinates.
 
  • #33
I think I'm not familiar with that. Actually sir this isn't in my course but I'm learning it because it seems so interesting plus your great explanations . Can you provide me with only the results of cubical element or if there is any source where I can find it so that I can look after , or maybe you tell me sir.
 
  • #34
Rahulx084 said:
I think I'm not familiar with that. Actually sir this isn't in my course but I'm learning it because it seems so interesting plus your great explanations . Can you provide me with only the results of cubical element or if there is any source where I can find it so that I can look after , or maybe you tell me sir.
See page 29 of http://web.mit.edu/2.25/www/pdf/viscous_flow_eqn.pdf
 
  • #35
can you just give me the result for stress tensor of cubical and parallelopiped one ? It would be so nice of you . Thanks
 
  • #36
Rahulx084 said:
can you just give me the result for stress tensor of cubical and parallelopiped one ? It would be so nice of you . Thanks
See Eqns. 43 of that same reference.
 

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