Pressure vs speed for liquids ?

  • Thread starter furkang
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  • #1
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Main Question or Discussion Point

pressure vs speed for liquids ? :(

Think of a pipe positioned horizontally.

Some fluid is flowing from left to right.(e.g. water)

Right side of the pipe is well narrower than left side.

Is the speed of a fluid particle at the right greater than the speed of a particle at the left?
What about their pressures?

(Perfect world no energy loss)
OR


perhaps I can NOT make such a comparison without considering any value constant.

--------------------------------------------------------------------------------------------------------------------------
I am really confused please help , basically I am looking for an example which prooves inverse proportion of speed and pressure of LIQUIDS. Can you give me an example like mine? Thank you for your help...
 

Answers and Replies

  • #2
Astronuc
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Let's assume an incompressible fluid - the density does not change - and apply conservation of mass.

[itex]\rho_1 * V_1 * A_1 = \rho_2 * V_2 * A_2 [/itex]

for incompressible flow [itex]\rho_1 = \rho_2 = \rho [/itex]

which then leaves [itex]V_1 * A_1 = V_2 * A_2 [/itex]

So what does the say about the relationship between fluid velocity (speed) and area?
 
  • #3
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ok that's well ...

that means fluid flows faster in the narrow section. That is completely different from my thought.
 
  • #4
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Is it the same if we use Bernoulli's equation to see that?

I could't see where is the pressure difference
 
  • #5
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Considering the fluid is incompressible, helps by making density constant. Is it the pressure difference, that causes the fluid to flow faster at the place where the pipe narrows???
 
  • #6
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You should take it the other way round(you should obviously apply Bernoulli's equation), that static head drop occurs due to increase in velocity head.
 

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