
[Sponsors] 
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
Rep Power: 9 
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
__________________
Top 4 tips 1. Knowledge is everything and Ignorance is dangerous. 2. Understand your limitations and try to eliminate them. 3. Get yerself a bike and hoon the chuffer. You will soon learn why dogs like to hang their heads out the car window. 4. Please before asking any questions on how to run simulations in CFX, go though all the tutorials 

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 
New Member
Join Date: Jul 2009
Posts: 2
Rep Power: 0 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
SIMPLE and energy equation convergence  Fabio  Main CFD Forum  0  June 1, 2007 06:06 
IRadiation Equation problem with CFX Parellel  Scott  CFX  2  January 9, 2007 21:39 
Form of energy Equation  Newbie  FLUENT  2  March 9, 2004 08:16 
how to disable energy equation for for nonnewton  yueroo  FLUENT  2  April 3, 2001 22:11 
Energy equation and Enthalpy  Martin  FLUENT  1  January 25, 2001 18:11 