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Old   October 25, 2007, 04:59
Default patch: nothing happened..!
  #1
sheila
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Hi,

I have a duct geometry.

I want to patch pressure at the inlet and outlet of the duct.

I marked the cells using adapt region and used the solve -> initialize -> patch.

I ran Fluent and after it converged I plot the pressure along the duct. It turned out that nothing happened. The pressure distribution remained the same.

Can you help me explain this problem.

Thank you

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Old   October 25, 2007, 09:34
Default Re: patch: nothing happened..!
  #2
bashu
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You are patching an initial guess or condition to the zones you have marked. If you don't change the BC you won't get a different answer just by patching. In transient you may get a different answer if your IC is changed.
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Old   October 25, 2007, 10:27
Default Re: patch: nothing happened..!
  #3
chun wee
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Hi Bashu,

Thanks for answering.

I ran the duct without the pressure patch (case I), after few thousands of iteration, I stopped iterating and recorded the results.

Then, I patched the pressure at duct inlet and outlet (case II).

Shouldn't these two give different results.

If not, then how is the correct procedure for patching pressure?

Thank you
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Old   October 25, 2007, 12:30
Default Re: patch: nothing happened..!
  #4
bashu
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If you are trying to model your case with different pressure drops you have to set it in BC panel.

Patching is for assigning a value to a ceratin zone at the beginning of your iteration but the zone won't maintain its value.

If I misunderstood your question, please explain more.
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Old   October 26, 2007, 00:13
Default Re: patch: nothing happened..!
  #5
sheila
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Hi Bashu,

I want to make a transient case, by changing the pressure at the inlet and outlet of the duct in the middle of iteration.

I did it like this:

Ran without patch -> stop iteration (plot the pressure) -> patch pressure at duct's inlet and outlet -> converge -> plot the pressure -> compare the two plot results

Is this correct? If not, can you please tell me the correct way of doing it?

Thank you

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