
[Sponsors] 
October 6, 2009, 11:34 
understanding the term: fvm::Sp(fvc::div(phi), h)

#1 
New Member
Dominik Christ
Join Date: Mar 2009
Posts: 28
Rep Power: 9 
Hello everyone,
when having a closer look at the energy equation as it is used by solvers for reacting cases, I cannot figure out where the term  fvm::Sp(fvc::div(phi), h) comes from. All I could find out is that it is a source term of some kind but when I try to derive an energy equation for enthalpy I do not get such a source term. Could anybody please enlighten me? :) Thanks in advance! Regards Dominik 

April 28, 2011, 11:37 

#2  
Senior Member
Daniel P. Combest
Join Date: Mar 2009
Location: St. Louis, USA
Posts: 581
Rep Power: 20 
Quote:
Dominik, I know this is an old thread, but I'm sure others run into it and have the same question. The origin of this term Sp(div(phi),h) comes from the expansion of the div(U,h) term in the transport equation. div(U,h) = h*div(U) + U&grad(h). In a completely converged domain the div(U) > 0. However, sometimes there is incomplete convergence and there is some generation (or consumption) that will throw off the energy balance. Have a look at origin of fvm::Sp(fvc::div(phi_), epsilon_) in kepsilon Eqn? and ScalarTransportFoam for RTD calculations for maybe a little explanation. Dan 

May 7, 2011, 05:53 

#3 
Member

Hi Dan, you mentioned that
which I cannot understand. For example, in an incompressible flow we may have div(U) = 0 everywhere. But how could you apply it to all the other cases? And what is the definition of U in you opinion? For example in two phase flow, will it be the velocity of each component or a mixed velocity? Or maybe there's no physics principle for div(U) = 0 at all? Is it a kind of restriction from mathematics? If possible, can you give me some references? Thx // Kai 

May 7, 2011, 08:14 

#4 
Member

Hi Foamers
again... about the div U =0... 'cause it's obviously correct in the simple singlephase incompressible flow. However if it comes to two phase flow, where there is a phase change term on RHS of eq. for instance in alphaEqn.H, it looks like Code:
ddt(alpha) + div(phi, alpha) == Gamma/rhoa //Kai 

Tags 
energy equation, source term 
Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
momentum source term  zwdi  FLUENT  13  December 5, 2013 18:58 
How to suppress the convective term  SAKTI  CDadapco  1  August 28, 2008 01:38 
UDF Source Term Units?  Brian  FLUENT  1  October 24, 2005 09:15 
pressure gradient term in low speed flow  Atit Koonsrisuk  Main CFD Forum  2  January 10, 2002 11:52 
bouyancy term in epsilon equation  Michael  Main CFD Forum  1  June 25, 1999 10:20 