
[Sponsors] 
June 23, 2006, 10:35 
I fell some trouble to impleme

#1 
Member
chris book
Join Date: Mar 2009
Posts: 85
Rep Power: 9 
I fell some trouble to implement a scalar transport eqn with the following source term:
C1*[grad(Xi)]^2  C2*epsilon/k * rho * Xi C1,C2: constants epsilon: turbulent dissipation k: turbulent kinetic energy Xi: scalar variable How do I have to implement this FOAM? 

June 23, 2006, 12:52 
the main problem is the realis

#2 
Member
chris book
Join Date: Mar 2009
Posts: 85
Rep Power: 9 
the main problem is the realistation of the squared gradient [grad(Xi)]^2
I have tried to do this like: volScalarField gradXiVar2 = fvc::grad(XiVar) & ... solve ( ...  fvm::Sp(...,gradXiVar2) ) but the following error occurs: > FOAM FATAL ERROR : incompatible fields for operation [XiVar]  [(grad(XiVar)&grad(XiVar))] How can I realise this squared gradient term? 

June 23, 2006, 12:54 
ups there is type
volScalar

#3 
Member
chris book
Join Date: Mar 2009
Posts: 85
Rep Power: 9 
ups there is type
volScalarField gradXiVar2 = fvc::grad(XiVar) & fvc::grad(XiVar) 

June 23, 2006, 13:25 
You've just for the the wrong

#4 
Senior Member
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,784
Rep Power: 22 
You've just for the the wrong way around:
In fvm::Sp, first put the multiplier and then the field you're solving for. Also, you seem to be confused by the meaning of things a bit:  first things first: C1*[grad(Xi)]^2 C1*magSqr(grad(Xi)). Done.  C1*[grad(Xi)]^2 is always positive, which makes it a source. Putting it into Sp will just harm your matrix structure. Thus, just leave it as a plain old field in the source  if you want to make C2*epsilon/k * rho * Xi, please tell me which variable you want to make it implicit in. In other words, what equation are you solving where this appears as the source term. I will assume you're solving for Xi: in this case, the Sp term would read: fvc::Sp(C2*epsilon/k*rho, Xi) Note that C2*epsilon/k*rho, is always positive and the minus in front of it makes this a sink term, so there's a point in making this an Sp. As you can see, the multiplier comes first and then the field (Xi) that you're solving for. Enjoy, Hrv
__________________
Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk 

June 24, 2006, 02:08 
thanks Hrv!
just to make su

#5 
Member
chris book
Join Date: Mar 2009
Posts: 85
Rep Power: 9 
thanks Hrv!
just to make sure I get you right: I want to solve a Xieqn and the problem is to implement the following source terms C1*[grad(XXi)]^2  C2*Xi the first term I already know from the XXiEqn so I think I can simply write C1*magSqr(fvc::grad(XXi)) the second term is always a sink (as you already mentioned) so an implicit formulation will advance the diagonal dominance of my matrix so you write fvc::Sp(C2*epsilon/k*rho, Xi) but why not fvm::Sp(C2*epsilon/k*rho, Xi) ??? Am I on the right way? 

June 24, 2006, 04:20 
Sorry, my fault: it should (of

#6 
Senior Member
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,784
Rep Power: 22 
Sorry, my fault: it should (of course) be fvm::Sp(C2*epsilon/k*rho, Xi)
Hrv
__________________
Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk 

August 14, 2007, 07:08 
Hi everybody
When i add a s

#7 
Senior Member
Marhamat Zeinali
Join Date: Mar 2009
Location: Tehran, Tehran, iran
Posts: 107
Rep Power: 9 
Hi everybody
When i add a source term (grad(Fi)) to momentum equation in icoFoam solver i get the below error Where: Gravity defined as Gravity [0 1 2 0 0 0 0] 9.81 and: volScalarField Fi = Gravity.value() * mesh.C().component(1) ; fvVectorMatrix UEqn ( fvm::ddt(U) + fvm::div(phi, U)  fvm::laplacian(nu, U) ); solve(UEqn == fvc::grad(Fi)fvc::grad(p)); .... SOURCE_DIR=. SOURCE=icoFoam.C ; g++ m32 Dlinux DDP Wall W Wnounusedparameter Woldstylecast O3 DNoRepository ftemplatedepth30 I/marhamat/OpenFOAM/OpenFOAM1.3/src/finiteVolume/lnInclude I/marhamat/OpenFOAM/OpenFOAM1.3/src/OpenFOAM/lnInclude IlnInclude I. fPIC pthread c $SOURCE o Make/linuxGcc4DPOpt/icoFoam.o icoFoam.C: In function 'int main(int, char**)': icoFoam.C:66: error: 'Fi' was not declared in this scope make: *** [Make/linuxGcc4DPOpt/icoFoam.o] Error 1 What is the matter? Thanks alot Marhamat 

August 14, 2007, 10:49 
The definition of Fi is inside

#8 
Senior Member
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,910
Rep Power: 27 
The definition of Fi is inside braces {}, so it's not accessible when it's used in the solve line.
Check where Fi is defined. Regards, A.
__________________
Alberto Passalacqua GeekoCFD  A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats. OpenQBMM  An opensource implementation of quadraturebased moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. 

August 25, 2007, 04:18 
Hello everybody
After running

#9 
New Member
morteza
Join Date: Mar 2009
Posts: 18
Rep Power: 9 
Hello everybody
After running the new icoFoam solver that changed by adding grad(Fi) as a source term , the vorticity magnitude increased with opposite of my expection . I used inlet and outlet for inlet&outlet boundries and other boundries are symmetryplane You can see the vorticitymag before and after of adding grad(Fi).I explaned Fi in my last message in this page. : : : Do you think i get correct result? An How i can decrease the vorticity magnitude? Have a nice weekend Marhamat 

August 25, 2007, 07:18 
Hi guys
I send the above mes

#10 
Senior Member
Marhamat Zeinali
Join Date: Mar 2009
Location: Tehran, Tehran, iran
Posts: 107
Rep Power: 9 
Hi guys
I send the above message with my friend. So anything is right. sorry for disturbing you Marhamat 

August 27, 2007, 06:04 
Ideas are welcome.(:
Thanks

#11 
Senior Member
Marhamat Zeinali
Join Date: Mar 2009
Location: Tehran, Tehran, iran
Posts: 107
Rep Power: 9 
Ideas are welcome.(:
Thanks alot 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Source term  Jony  FLUENT  3  January 17, 2009 18:44 
Source term  mayur  FLUENT  0  August 10, 2004 13:23 
source term  zwdi  FLUENT  2  May 26, 2004 10:34 
the source term  neil  CFX  10  July 15, 2002 17:10 
source term  fouzi  FLUENT  0  April 13, 2000 11:56 