Integral Equation to Foam Equation

Thilo · October 25, 2011, 14:32

Hi Everyone,

can someone please tell me, if I have implemented my equation right? As this is my first task I implement into openFoam, I'm not sure wether there are errors in my code which is running so far, but crashes after some timesteps.

My Equation is:

$\frac{\partial}{\partial t}\int f_i d V + \int{f_i \vec U \vec n}dA+\rho\int{U_i \vec U \vec n}dA +\int{p \vec e\cdot \vec n}dA$

with f: velocity times density
U: velocity
p: pressure

My OpenFoam code is:

fvVectorMatrix aFEeqn
(
fvm::ddt(aF)
+ fvm::div(ac_phi,aF)
+ rho * fvc::div(ac_phi_2,U)
+ fvc::grad(aP)
);

Thank you very much in advanced,

Thilo

chegdan · November 22, 2011, 18:01

You may have answered this already, but to make your question a little clearer...why not write it using latex (http://www.cfd-online.com/Forums/sit...ne-forums.html).

Code:

\oint_{S} \vec{U}\vec{U}\cdot \hat{n}dA

produces

$\oint_{S} \vec{U}\vec{U}\cdot \hat{n}dA$

see link above for more explanation

Cyp · November 24, 2011, 03:17

What about the pressure equation ?

Indeed, your equation depends on the pressure field. Consequently the pressure must be evaluated elsewhere.

The classical method is to use SIMPLE or PISO algorithms.. (cf simpleFoam or pisoFoam or icoFoam)

regards,
Cyp

Thilo · November 24, 2011, 04:53

Hi Cyp,

thanks for this advice. Indeed there is a pressure and a density equation, which I didn't mention. I was not shure, if I implemented the mentioned equation right and I didn't want to ask for to much help.

Meanwile I solved my problem!

With kind regards,

Thilo

October 25, 2011, 14:32	Integral Equation to Foam Equation	#1
Thilo New Member Thilo Michels Join Date: Oct 2011 Posts: 11 Rep Power: 14	Hi Everyone, can someone please tell me, if I have implemented my equation right? As this is my first task I implement into openFoam, I'm not sure wether there are errors in my code which is running so far, but crashes after some timesteps. My Equation is: $\frac{\partial}{\partial t}\int f_i d V + \int{f_i \vec U \vec n}dA+\rho\int{U_i \vec U \vec n}dA +\int{p \vec e\cdot \vec n}dA$ with f: velocity times density U: velocity p: pressure My OpenFoam code is: fvVectorMatrix aFEeqn ( fvm::ddt(aF) + fvm::div(ac_phi,aF) + rho * fvc::div(ac_phi_2,U) + fvc::grad(aP) ); Thank you very much in advanced, Thilo Last edited by Thilo; November 23, 2011 at 04:06. Reason: Equation in latex form

November 22, 2011, 18:01		#2
chegdan Senior Member Daniel P. Combest Join Date: Mar 2009 Location: St. Louis, USA Posts: 621 Rep Power: 0	You may have answered this already, but to make your question a little clearer...why not write it using latex (http://www.cfd-online.com/Forums/sit...ne-forums.html). Code: \oint_{S} \vec{U}\vec{U}\cdot \hat{n}dA produces $\oint_{S} \vec{U}\vec{U}\cdot \hat{n}dA$ see link above for more explanation

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November 24, 2011, 03:17		#3
Cyp Senior Member Cyprien Join Date: Feb 2010 Location: Stanford University Posts: 299 Rep Power: 18	What about the pressure equation ? Indeed, your equation depends on the pressure field. Consequently the pressure must be evaluated elsewhere. The classical method is to use SIMPLE or PISO algorithms.. (cf simpleFoam or pisoFoam or icoFoam) regards, Cyp

November 24, 2011, 04:53		#4
Thilo New Member Thilo Michels Join Date: Oct 2011 Posts: 11 Rep Power: 14	Hi Cyp, thanks for this advice. Indeed there is a pressure and a density equation, which I didn't mention. I was not shure, if I implemented the mentioned equation right and I didn't want to ask for to much help. Meanwile I solved my problem! With kind regards, Thilo