Hi Friends,
I have a proble
Hi Friends,
I have a problem of the Vector and scalar when I process the Darcy velocity. The Darcy velocity is depended on the gradient of pressure. Pressure is the SCALAR, but Darcy VELOCITY is the VECTOR. So when I complier, I was told the operator is error. My equation of the Darcy velocity is: U = K/nu(grad(P)  rho*g) where K is the permeability, nu is the viscosity, P is pressure and g is gravity. I encoded as followsing in FOAM: fvVectorMatrix UEqn // solving Darcy velocity (  (K/nu)*(fvc::grad(P)  rho*g) ); UEqn.solve(); The complier error is: buoyantFoam.C:81: error: no match for 'operator' in 'Foam::fvc::grad(const Foam::GeometricField<type,>&) [with Type = Foam::scalar]()  Foam::operator*(const Foam::GeometricField<foam::scalar,>&, const Foam::GeometricField<type,>&) [with Type = Foam::scalar, PatchField = Foam::fvPatchField, GeoMesh = Foam::volMesh](((const Foam::GeometricField<foam::scalar,>&)((const Foam::GeometricField<foam::scalar,>*)(& gh))))' /home/liu/OpenFOAM/OpenFOAM1.2/src/OpenFOAM/lnInclude/dimensionSet.H:176: note: candidates are: Foam::dimensionSet Foam::operator(const Foam::dimensionSet&) /home/liu/OpenFOAM/OpenFOAM1.2/src/OpenFOAM/lnInclude/dimensionSet.H:188: note: Foam::dimensionSet Foam::operator(const Foam::dimensionSet&, const Foam::dimensionSet&) /home/liu/OpenFOAM/OpenFOAM1.2/src/OpenFOAM/lnInclude/dimensionedScalar.H:55: note: Foam::dimensionedScalar Foam::operator(const Foam::dimensionedScalar&, Foam::scalar) /home/liu/OpenFOAM/OpenFOAM1.2/src/OpenFOAM/lnInclude/dimensionedScalar.H:56: note: Foam::dimensionedScalar Foam::operator(Foam::scalar, const Foam::dimensionedScalar&) /home/liu/OpenFOAM/OpenFOAM1.2/src/cfdTools/general/lnInclude/initContinuityErr s.H:38: warning: unused variable 'cumulativeContErr' make: *** [Make/linuxGcc4Opt/buoyantFoam.o] Error 1 Could any friend help me? Thanks so much. 
Is it possible, that your g is
Is it possible, that your g is only a scalar? It should be a vector (gravity is pointing somewhere).

Why are you building a matrix
Why are you building a matrix when the equation is explicit?
In any case, you haven't included U in the UEqn. What do you think you will be solving for? 
Hi, freinds,
Many thanks fo
Hi, freinds,
Many thanks for your help. I solve the UEqn for the Darcy`s velocity which is depended on the gradient pressure and gravity (for buoyancy). My whole solver is linked by (http://www.cfdonline.com/cgibin/Op...cus/discus.cgi). So if not like my wroten, what it should be? Could you give more advice? Thanks again. 
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