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April 2, 2014, 23:00 
Questions about the energy equation

#1 
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Peter Aestas
Join Date: Dec 2013
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Dear all, i got two problems
1.in fluent6.3 help manual, i saw the energy equation form like this in the picture,so my question is, does that means i should make the energy equation(take temperature as an argument) into this form(take E as an argument) ,then use UDF to define the source and diffusivity term? 2.A friend of me said, if the energy equation is used in fluent, fluent will take pressure and kinetic energy effect term into consideration automatically,so i don't need to write the pressure and kinetic energy effect term of momentum equation into my udf.Does that true?Where can i find the proof? Thank you so much~ 111.jpg 

April 4, 2014, 15:52 

#2 
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François Grégoire
Join Date: Jan 2010
Location: Laval University, Canada
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From Fluent Theory Guide 15.0:
5.2.1.4. Inclusion of Pressure Work and Kinetic Energy Terms Equation 5.1 (p. 134) includes pressure work and kinetic energy terms, which are often negligible in incompressible flows. For this reason, the pressurebased solver by default does not include the pressure work or kinetic energy when you are solving incompressible flow. If you want to include these terms, use the define/models/energy? text command. When asked to include pressure work in energy equation? and include kinetic energy in energy equation?, respond by entering yes in the console window. Pressure work and kinetic energy are always accounted for when you are modeling compressible flow or using the densitybased solver. 

April 5, 2014, 05:24 

#3  
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Peter Aestas
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Quote:


April 5, 2014, 10:17 

#4 
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François Grégoire
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Location: Laval University, Canada
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I'm not sure to understand what you want to do, add a source term to the momentum equation? Then you write whatever source term you want to add to the momentum eqn, you don't have to 'handle' anything. The pressure term in the momentum is there and, in my limited experience in fluid mechanics, I've never heard of a case where this term is not included, it sounds unphysical to me, there has to be a pressure gradient so that the fluid moves.


April 5, 2014, 21:05 

#5  
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Peter Aestas
Join Date: Dec 2013
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Quote:
My momentum equation is like this below,the argument u and Ti are velocity and temperature for ions, and Te are temperature for electrons(i defined plasma as single fluid of ions.So Te is defined as UDS). the right side of this equation is the source term of momentum, and according to P=nkT,the first ▽(nikTi) is the grad P. Someone told me, if the energy equation is used in fluent. Fluent will take grad P term of momentum equation into consideration, so i only need to put the last two terms ▽(nekTe)+jx(Bself+Bad) into DEFINE_SOURCE marco. I don't know whether this is ture or not. 2222.jpg 

April 6, 2014, 11:28 

#6 
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François Grégoire
Join Date: Jan 2010
Location: Laval University, Canada
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Sorry, I know next to nothing in electrons/ions transport, I can't help. Good luck.


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