Forces appearing on the pipe when a fluid flows in it

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Discussion Overview

The discussion centers on understanding the forces that act on a pipe when fluid flows through it, particularly in relation to linear momentum and fluid dynamics. Participants explore concepts such as pressure, drag, and shear stresses in the context of fluid flow within a pipe.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses confusion about how forces can appear on a pipe when fluid flows through it, questioning the relationship between fluid momentum and forces on the pipe.
  • Another participant explains that pressure acts perpendicular to the pipe surface and that fluid drag acts parallel to it, noting that changes in fluid direction result in changes in momentum, which the pipe must react to.
  • A subsequent post reiterates the previous points about pressure and drag, suggesting that viscous effects may cause the fluid to apply a force to the pipe in the direction of flow, potentially arising from shear strain.
  • Another participant states that viscous flow leads to shear stresses on the pipe.

Areas of Agreement / Disagreement

Participants present multiple viewpoints regarding the forces on the pipe, particularly concerning the roles of pressure, drag, and shear stresses. The discussion remains unresolved, with no consensus on the exact nature of the forces involved.

Contextual Notes

The discussion does not clarify the assumptions regarding fluid properties, flow conditions, or the specific definitions of terms like shear strain and viscous flow, which may affect the understanding of the forces on the pipe.

mech-eng
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Hi, I study linear momentum. But I cannot understand enough that how can forces appear on a pipe when fluid flows in the pipe? Fluid have a momentum as m*v how can forces appear on the pipe. I cannot demonstrate the situation in my mind. How can I find a demonstration or a free body diagram for this.

In another words, if a fluid have momentum while entering and going out of a pipe, why are there forces on the pipe?

Thank you.
 
Last edited:
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Perpendicular to the pipe surface is the pressure in the fluid. Parallel to the pipe surface is fluid drag on the pipe surface. If there are any changes in direction along the pipe those changes in direction cause changes in the fluid's momentum. The pipe reacts to those changes in momentum where the direction changes occur.
 
OldYat47 said:
Perpendicular to the pipe surface is the pressure in the fluid. Parallel to the pipe surface is fluid drag on the pipe surface. If there are any changes in direction along the pipe those changes in direction cause changes in the fluid's momentum. The pipe reacts to those changes in momentum where the direction changes occur.

Then can we say that when a fluid flowing in a pipe, probably because of viscous effects, fluid apply a force to the pipe in the direction of flow. Is this force appear from shear strain?

Thank you.
 
It is a viscous flow that gives rise to shear stresses on the pipe.
 

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