No Slip Condition: Which is Correct? Explained

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SUMMARY

The discussion centers on the "No Slip Condition" in fluid dynamics, specifically addressing conflicting statements from two textbooks regarding fluid velocity at a solid boundary. One source claims that the fluid's velocity matches the solid boundary's velocity, while the other asserts that the fluid's velocity is zero at the boundary. The consensus among participants is that the second statement is correct, as it aligns with the principle that the fluid in contact with a solid boundary has zero velocity relative to that boundary, regardless of the boundary's motion.

PREREQUISITES
  • Understanding of fluid dynamics principles
  • Familiarity with the No Slip Condition
  • Knowledge of relative velocity concepts
  • Basic grasp of boundary layer theory
NEXT STEPS
  • Research the No Slip Condition in fluid mechanics
  • Study the implications of boundary layer theory on fluid flow
  • Examine different fluid dynamics textbooks for varying interpretations
  • Learn about relative velocity in moving reference frames
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Students and professionals in fluid dynamics, mechanical engineers, and anyone seeking to clarify the principles of fluid behavior at solid boundaries.

foo9008
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Homework Statement


i was told that

For a given fluid the velocity of fluid in contact with with solid boundary is equal to the velocity of solid boundary in a book . In another book , I was told that the velocity of fluid at the solid boundary is 0 , which is correct ? can someone explain ?

Homework Equations

The Attempt at a Solution


imo , the first one is wrong , the second statement is correct , am i right ? can someone expalin pls?
 
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Taken at face value the first statement allows for the solid boundary to be moving and the second statement assumes that it is not moving . In either case the velocity of the fluid in contact with the solid boundary is zero relative to the boundary .

We really need to see the actual text from the books though to be certain about what is being said about this .
 
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The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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