# mass transport having different diffusity in each direction

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November 8, 2013, 06:27
mass transport having different diffusity in each direction
#1
New Member

Baek, Donghae
Join Date: Jan 2013
Location: Seoul
Posts: 24
Rep Power: 5
hello foamer

I am making my own solver related to mass transport in turbulent flow.

first, i made the solver of mass transport having same diffusity of concentration in each direction like:

fvScalarMatrix CEqn
(
fvm::ddt(C)
+ fvm::div(phi, C)
- fvm::laplacian(turbulence->nut() / 0.5, C)

);

CEqn.solve();

the code above is added pimple solver to calculate concentration C.

this solver is for river flow and turbulent diffusity of mass is

nut() / 0.5

it is eddy-viscosity over Prandtl number(in this case, Prandtl number is 0.5)

that is, mass spread out having same diffusion coefficient in x,y,z

but now, i want to consider different coefficient in each direction like attached equation.

different coefficient is definded D1, D2, D3 as scalar.

D1, D2, D3 is calculated by some equations.

if scalar value D1, D2, D3 can be located in vector matrix after D1,D2,D3 is calculated, i think it is easy to programming as i want.
like:
Dt=(D1, D2, D3)
//////////////////////////////////////////////////////////
fvScalarMatrix CEqn
(
fvm::ddt(C)
+ fvm::div(phi, C)
- Dt&fvm::laplacian( C)

);

CEqn.solve();
///////////////////////////////////////////////////////////

actually i dont know openfoam programming exactly.
I am just beginer for programming.
so i'm not sure whether - Dt&fvm::laplacian(C) is right expression in openfoam language or not

plz help me.

the point is make vector using scalar which is calculated
Attached Images
 eq1.png (10.9 KB, 17 views)

 February 10, 2014, 10:01 #2 Senior Member   Joachim Herb Join Date: Sep 2010 Posts: 383 Rep Power: 11 If you haven't solved your problem meanwhile: Here is the documentation of the OpenFOAM operators: http://www.foamcfd.org/Nabla/guides/...sGuidese4.html

 February 21, 2014, 16:45 #3 New Member   Jay Join Date: Mar 2011 Posts: 1 Rep Power: 0 Did you ever figure this out? What is the syntax to access the components of the vector Dt in fvScalarMatrix? Last edited by jdmac6; February 25, 2014 at 11:59.

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