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Old   January 30, 2014, 11:21
Default Adding extra terms in governing equations
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Smith
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Dear friends,
Is it possible in CFX to add one or two extra terms in to governing equations? for example adding pressure gradient term to energy equation and CFX solves the modified energy equation containing pressure gradient term.

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Old   January 30, 2014, 18:02
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Glenn Horrocks
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You cannot modify the underlying equations. Your options are:
* If you can write it as a source term then use a source term
* Find an existing CFX physical model which is close and use that.
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Old   January 30, 2014, 23:26
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Thank you Glenn,
In your idea can we present the pressure gradient as a source term ?

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Old   January 31, 2014, 00:05
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Yes, you certainly can use the pressure gradient in a source term. You can get the gradient of the pressure field with p.grad, and I think to get the components it is p.grad_x.
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Old   January 31, 2014, 17:51
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Dear Alek,

I am bit puzzled by your question. What heat transfer model are you using Thermal Energy, or Total Energy ?

If you are using the Thermal Energy model, I wonder what are you trying to achieve? What type of material are you using ? incompressible ? I would suggest to contact ANSYS support and check if there is already a mechanism to activate such term.

In the case of the Total Energy model, CFX already include the pressure gradient term; therefore, you may be double accounting such effect.

Still puzzled
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Old   January 31, 2014, 23:26
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Dear opaque
In fact I want to add pressure gradient term to species transport equation. My problem is compressible.

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Old   February 10, 2014, 13:21
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Dear Alek,

CFX nor FLUENT include the pressure gradient term in the species diffusion flux. FLUENT includes the thermal diffusion gradient though.

Keep in mind these additional terms are not trivial volumetric sources, but fluxes about the control volumes and must be discretized accordingly.

You may need to contact ANSYS (CFX / FLUENT) for support on how to implement such terms.
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