# phi in scalarTransportFoam, why not U

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 September 4, 2015, 07:10 phi in scalarTransportFoam, why not U #1 New Member   novo Join Date: Jun 2015 Posts: 11 Rep Power: 8 Dear Openfoamers, sorry for the ignorant question but I would appreciate if anybody could revert me to the proper info since I have been looking around and am still quite puzzled. In the scalarTransportFoam the equation to be solved includes the scalar "T" which is transported both by diffusion constant ("DT") and convection vector ("U"). But in the scalarTransportFoam the equation solved includes "phi" instead of "U". Code: ``` for (int nonOrth=0; nonOrth<=nNonOrthCorr; nonOrth++) { // Building and solving the scalar tranport equation solve ( fvm::ddt(T) // Unsteady term + fvm::div(phi, T) // Convective term - fvm::laplacian(DT, T) // Diffusive term ); }``` Could anyone help me?

December 18, 2015, 17:14
#2
Senior Member

Thomas Oliveira
Join Date: Apr 2015
Posts: 114
Rep Power: 9
Quote:
 Originally Posted by pnovo in the scalarTransportFoam the equation solved includes "phi" instead of "U". Could anyone help me?
"phi" is the scalar product of the of Uf and the area vector. Uf is the velocity at the face, while U is the velocity at the the center of the cell. If you used U at the discretized form of the divergence, you would have the divergence equals to zero no matter how your velocity field were.

 Tags openfaom, scalartransportfoam