# Calculus syntax

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 April 28, 2006, 12:25 I am wondering if some is able #1 Member   chris book Join Date: Mar 2009 Posts: 85 Rep Power: 8 I am wondering if some is able to "translate" me the code in a more mathematican way. phi = fvc::interpolate(rho) *((fvc::interpolate(U) & mesh.Sf()) - fvc::meshPhi(rho, U)); > what is phi in this context? I do not understand how it is computed! for (int nonOrth=0; nonOrth<=nNonOrthCorr; nonOrth++) { fvScalarMatrix pEqn ( fvm::ddt(psi, p) + fvc::div(phi) - fvm::laplacian(rho*rUA, p) ); >How to determine this equation? I think this is PISO related stuff. pEqn.solve();

 April 29, 2006, 09:26 Hi Chris, in foam usually a #2 Senior Member   Markus Hartinger Join Date: Mar 2009 Posts: 102 Rep Power: 8 Hi Chris, in foam usually all variables are stored at the cell centre. But for calculating the divergence of a field the face values are needed. So fvc::interpolate returns a field containing the face values interpolated from the cell-centre values. The interpolation scheme is defined in system/fvScheme by the entry interpolationScheme, usually linear. phi is in your example the mass-flux across the faces corrected for mesh-motion by fvc::meshPhi. the pEqn is part of PISO, probably you look in one of the foam thesis' for it's derivation or ferziger and peric regards Markus

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