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June 14, 2009, 22:45 
Need help:about energy equation in CFX

#1 
New Member

In CFX,two kinds of energy equation has been provided,i.e.Thermal energy equation and Total enthapy equation.SO ,my question is about two equations as follows?
Firstly:In theory ,two equations are equal,but why CFX provides these two options.What conditions can these two equations be used. Secondly:In CFX_help documentation,only total enthapy equation for muticomponent condition has been presented and described .So,does it mean only total enegy equation can be applied for muticomponent,but Thermal energy eqaution not. Thirdly.If I use Thermal energy equation to simulate combustion ,is there any reaction heat source term in this equation.Or,I wonder if combustion model is activated ,CFX will add heat source term to the equqtion automaticly? Finnally.I hope someone can give me detalied explanation about the difference between these two equation and If I use total enthapy equation to simulate combustion ,is it all right? 

June 15, 2009, 02:32 

#2 
Senior Member
George
Join Date: Mar 2009
Location: Birmingham, UK
Posts: 257
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the two energy models are not the same and nowhere in the documentation is saying that
check the combustor totorial to learn how to setup combustion. if the reactions you want are not in the standard libary you need to provide cfx with kinetic data in an nutshel use total energy if you have high speed flows or phase change
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June 15, 2009, 09:34 

#3 
New Member

In theory,energy equation has a few representation styles,i.e.temperture as variable,thermal energy ,static ehthalpy ,or total enthalpy as variable and so on.
Also, these styles can be transformed to each other,so they are actual equal in theory.But when they present in CFD,they become not the same,and should be used in certain condition,why? Particularly, in CFX ,only total enthalpy equation has been derived and described in multicomponent part of HELP documentation,does it mean thermal energy cant be used to modeling multicomponent flow? And combustion actually can be treated as multicomponent reaction flow.So,the total enthalpy equation should be used to combustion modeling,isn't it? At last ,I wanna know if thermal energy equation is used to model combution,is there reaction heat source term in thermal energy eqaution or just a eqaution without source term like total enthalpy eqaution. 

June 24, 2009, 20:44 

#4 
New Member

Someone help me answer this question ,Thank you


July 2, 2009, 22:31 

#5 
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