# Writing equations

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 October 12, 2011, 09:38 Writing equations #1 Member   Join Date: Jun 2011 Posts: 39 Rep Power: 8 Sponsored Links I have a question regarding how the Navier-Stokes is formulated in icoFoam.C file. fvVectorMatrix UEqn ( fvm::ddt(U) + fvm::div(phi, U) - fvm::laplacian(nu, U) ); solve(UEqn == -fvc::grad(p)); Above, all density terms are simplified except the one included in phi (phi = rho x U). How is this possible? Shouldn't it be something like below: fvm::ddt(rho, U) + fvm::div(phi, U) - fvm::laplacian(mu, U) == - fvc::grad(p)

 October 12, 2011, 11:34 #2 Senior Member   David Gaden Join Date: Apr 2009 Location: Winnipeg, Canada Posts: 436 Rep Power: 15 In icoFoam, since density is uniform and constant, it is pulled out of the equation. Even "phi" is actually volume flux. __________________ ~~~ Follow me on twitter @DavidGaden Last edited by marupio; October 12, 2011 at 11:34. Reason: Even "rho" is... changed to Even "phi" is

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