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Adding a scalar transport equation to buoyantPimpleFoam

Hello Everyone,

I am trying to add a scalar transport equation to buoyantPimpleFoam, which is a compressible solver.

Code:

     fvScalarMatrix rhoEEqn

     (

         fvm::ddt(rhoE)              

       + fvm::div(phi, rhoE)       

       - fvm::laplacian(a, rhoE)   

     );

     rhoEEqn.solve();

I get the following dimension mismatch error.

Code:

  --> FOAM FATAL ERROR: 

incompatible dimensions for operation 

    [rhoE[0 -3 0 0 0 1 0] ] + [rhoE[1 -6 0 0 0 1 0] ]



    From function void Foam::checkMethod(const  Foam::fvMatrix<Type>&, const Foam::fvMatrix<Type>&,  const char*) [with Type = double]

     in file /home/user/OpenFOAM/OpenFOAM-6/src/finiteVolume/lnInclude/fvMatrix.C at line 1283.

In order find out the source of error, I ran the simulation by neglecting the terms in scalar transport equation, one by one.

The error pops up when the divergence term is included.

I was able to successfully add this scalar equation to buoyantBoussinesqPimpleFoam (incompressible solver).

The dimension of rhoE is [0 -3 1 0 0 1 0]

Does adding a scalar transport equation to a compressible solver, need any special modification?

Is the dimension of phi different in a compressible sovler?

Unfortunately, I could not find any tutorial on adding a scalar transport equation to a compressible solver.

Kindly, please give me a direction in solving this.

Thank You.

With Thanks,
Pavithra.

Hi,

if you have a passive scalar transport equation the general equation is:

$\frac{\partial \rho \phi}{\partial t} + \nabla \bullet (\rho \textbf{U} \phi) = S_\phi$

Thus, the time derivative in FOAM should have the following:

Code:

fvm::ddt(rho, rhoE)

The unit mismatch is based on the missing density.

Quote:

Originally Posted by Tobi (Post 738047)

Code:

fvm::ddt(rho, rhoE)

The unit mismatch is based on the missing density.

Respected Sir,

Thank you so much for your kind help. I followed your advice and defined the scalar transport equation as below

Code:

     fvScalarMatrix rhoEEqn

     (

         fvm::ddt(rho, rhoE)                 //Time derivative

       + fvm::div(phi, rhoE)        //Convective term

       - fvm::laplacian(a*rho, rhoE)    //Diffusive Term

     );

      rhoEEqn.solve();

Now, I am able to successfully run the simulation and validate the solver.

Thank You.

With Thanks,
Pavithra.

Quote:

Originally Posted by Pavithra (Post 738031)

Hello Everyone,

I am trying to add a scalar transport equation to buoyantPimpleFoam, which is a compressible solver.

What about using the scalarTransport functionObject instead?

Hi Mark,

the function object is a possible and very easy option, I agree. Also the fields should be available during run-time while you can lookup the quantity and re-use it whereever you want.

Crazy how powerful the function objects are.

Respected Prof. Mark Olesen,

Thank you so much for your suggestion. I am very new to OpenFoam. Could you please give me some direction for me to learn about functionObjects. I am interested in learning about that and solve a scalar transport equation using fucntionObject.

Thank You.

With Thanks,
Pavithra.

Hello Everyone,

I tried to use functionObject to solve a scalar transport equation as suggested by Dr. Mark Olesen. I was able to do it successfully.

Now I have a transport equation, which has two convective fluxes. I am puzzled, if I can solve this using functionObject. My base solver is buoyantPimpleFoam and I use OF v6.

My transport equation is

$\frac{\partial \phi}{\partial t} + \nabla \bullet (\textbf{U} \phi) + \nabla \bullet (\textbf{A} \phi) - \alpha \nabla^2 \phi = 0$

Here,

$\phi$ - Electric charge density
$\textbf{U}$ - velocity
$\textbf{A}$ - flux field defined by user
$\alpha$ - Diffusion coefficient

Kindly, please give me a direction to solve this.

I want to define a source term which is dependent on this scalar ( $\phi$ ).

Thank You.