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help! Mass flow outlet again

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Old   April 9, 2003, 10:11
Default help! Mass flow outlet again
  #1
Z. T.
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Hello,

In my project, mass-flow-rate in outlet is needed. I have ever tried using the scheme file someone posted before to do that. However, a error in Fluent6 is shown as follows:

Loading "E:\mesh ind\mesh4\mfo.scm"

Error: eval: unbound variable Error Object: )

what does give rise to this error? The scheme file is based on Fluent/UNS. Could anyone help me get one for Fluent5/6?

Thanks!

zheng
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Old   April 9, 2003, 10:17
Default Re: help! Mass flow outlet again
  #2
HVN
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Hello

Why don't you use the surface monitor for that in fluent 6 ?

HV
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Old   April 9, 2003, 10:39
Default Re: help! Mass flow outlet again
  #3
HVN
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or report with surface integral
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Old   April 9, 2003, 10:54
Default Re: help! Mass flow outlet again
  #4
Z. T.
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Hi HVN

Thank you for your suggestion. In my case, only pressure in inlet and mass flow rate in outlet is known. so I need special boundary condition.

please see the message as follows:

http://www.cfd-online.com/Forum/flue....cgi?read=1224

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Old   April 9, 2003, 11:33
Default Re: help! Mass flow outlet again
  #5
Ahmed
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There is no mass flow out boundary condition..In the same time out flow boundary condition cannot be used with compressible flow..therefore I suggest to use pressure outlet BC then you can monitor the mass flow at the outlet then ajust the pressure to get the required mass flow.
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Old   April 9, 2003, 12:24
Default Re: help! Mass flow outlet again
  #6
Z.T.
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Hello Ahamed:

Thank you for your advice. I think it is good idea. I am thinking, can I prescribe velocity magnitude in outlet by using velocity-inlet(set flow direction as -1)? Is this a way to solve the problem?

Thanks!

zheng
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Old   April 10, 2003, 04:42
Default Re: help! Mass flow outlet again
  #7
Hendawi Mohamed
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Hello fluently,

I think that in your case, the better solution is to specify a target-mass-flow-rate with pressure-outlet as boundary condition (Cf. /help/html/ug/node198.htm).

for more information you can refer to these messages posted in response to Thierry who is almost in the same case as yours.

http://www.cfd-online.com/Forum/fluent.cgi?read=12288

cordially

Mohamed

P.S.: With Fluent 6 this option is Ok but I don't know if there is some restriction in Fluent 5,
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Old   April 10, 2003, 05:18
Default Re: help! Mass flow outlet again
  #8
Thierry
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Hello !

Mohamed is right, with FLUENT 6.1.18 you can specify a target-mass-flow-rate with pressure-outlet BC...it's a little bit slow but it seems working.

Thierry.
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Old   April 10, 2003, 05:35
Default Re: help! Mass flow outlet again
  #9
Z. T.
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Hello Mohamed and Thierry:

Thank you for your help! I am tring to do that.

By the way, I want to ask a question: My project is 2D. In this case, is the depth per unit length(1m) in Fluent by default? I need this value to calculate mass flow rate corresponding to 2D geometry.

Thanks!
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Old   April 10, 2003, 08:51
Default Re: help! Mass flow outlet again
  #10
Ahmed
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(1)You can specify the profile..

(2)Sure It is 1m, Actually it is convention everywhere..
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Old   April 10, 2003, 08:55
Default Re: help! Mass flow outlet again
  #11
Volker Pawlik
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it is always 1 m independet from what you set in reference values panel!!!

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Old   April 10, 2003, 08:59
Default Re: help! Mass flow outlet again
  #12
Volker Pawlik
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I must correct my answer to be better understandable:

The massflow you set must be the massflow for a depth of 1 m, independent from what you set as reference depth. Fluent calculates the corresponding massflow for your reference depth!!

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Old   April 10, 2003, 12:27
Default Re: help! Mass flow outlet again
  #13
Z.T.
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Thanks to all!
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