# Hentalpy equation openfoam - miss a term

 Register Blogs Members List Search Today's Posts Mark Forums Read

 March 4, 2010, 11:15 Hentalpy equation openfoam - miss a term #1 New Member   Emanuele Leoni Join Date: Apr 2009 Posts: 13 Rep Power: 9 Hi, i'm working on my master thesis in wich i'm trying, starting from a SimpleFoam solver (steady, not transient), to programming in openfoam the ED, EDC and flamelets models in the way to compare the results with fluent and maybe in the future be able to use OF instead of fluent. I made the EDmodel and tested it on the sandia simple flames: the results are quite good, but not excellent: the fluent flame has a higher peak and is more dissipative, and the difference seems to increase when the fuel inlet velocity decrease. In my opinion there is something wrong in the enthalpy equation. Looking in the fluent user guide (http://my.fit.edu/itresources/manual...e568.htm#86361) we can see a term in the equation, named sensible enthalpy, that is the dissipation term due to the enthalpy of the single species. This term is not in the hEqn file of Openfoam: Code: ```fvScalarMatrix hEqn ( fvm::div(phi, h) - fvm::Sp(fvc::div(phi), h) - fvm::laplacian(turbulence->alphaEff(), h) -fvc::div(lambda*fvc::grad(TT)) == fvc::div(phi/fvc::interpolate(rho)*fvc::interpolate(p)) - p*fvc::div(phi/fvc::interpolate(rho))``` The point is that i'm not able to add this term, because i really don't know how to access to the single elements enthalpy. Probably my flame will not change with this therm and the differences will be the same but i want to try also in this way.... Thank you Emanuele Leoni

August 17, 2010, 14:32
#2
New Member

Silvano
Join Date: Aug 2010
Location: Chicago /Torino Us/Italy
Posts: 11
Rep Power: 8
Quote:
 Originally Posted by lions85 Hi, i'm working on my master thesis in wich i'm trying, starting from a SimpleFoam solver (steady, not transient), to programming in openfoam the ED, EDC and flamelets models in the way to compare the results with fluent and maybe in the future be able to use OF instead of fluent. I made the EDmodel and tested it on the sandia simple flames: the results are quite good, but not excellent: the fluent flame has a higher peak and is more dissipative, and the difference seems to increase when the fuel inlet velocity decrease. In my opinion there is something wrong in the enthalpy equation. Looking in the fluent user guide (http://my.fit.edu/itresources/manual...e568.htm#86361) we can see a term in the equation, named sensible enthalpy, that is the dissipation term due to the enthalpy of the single species. This term is not in the hEqn file of Openfoam: Code: ```fvScalarMatrix hEqn ( fvm::div(phi, h) - fvm::Sp(fvc::div(phi), h) - fvm::laplacian(turbulence->alphaEff(), h) -fvc::div(lambda*fvc::grad(TT)) == fvc::div(phi/fvc::interpolate(rho)*fvc::interpolate(p)) - p*fvc::div(phi/fvc::interpolate(rho))``` The point is that i'm not able to add this term, because i really don't know how to access to the single elements enthalpy. Probably my flame will not change with this therm and the differences will be the same but i want to try also in this way.... Thank you Emanuele Leoni

Hi Emanuele,
I have your same problem, have you understood what is happening there? do you find some solution? It would really help me :-)

Thank you
Silvano Pautasso

 August 18, 2010, 12:12 #3 Member   MSR CHANDRA MURTHY Join Date: Mar 2009 Posts: 32 Rep Power: 9 Exactly i had the same problem, when i tried the reactingfoam. Apparently i tried a reacting mixing layer problem [barrows&Kurkov]. the thermal diffusion is less in foam, giving a thin flame. I guessed something may be wrong with enthalpy equation., i could not go further deep into the code. [QUOTE=lions85;248573]Hi, the fluent flame has a higher peak and is more dissipative, and the difference seems to increase when the fuel inlet velocity decrease. In my opinion there is something wrong in the enthalpy equation.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post jannnesss CFX 0 January 8, 2010 20:53 bernarde STAR-CCM+ 0 June 4, 2009 03:17 Micael Boulet FLUENT 3 July 31, 2008 18:32 Valdemir G. Ferreira Main CFD Forum 0 April 30, 2000 08:57 Michael Main CFD Forum 1 June 25, 1999 10:20

All times are GMT -4. The time now is 18:09.