[MCrossover97]

Hey everybody!

I want to simulate 1D steady state flow in porous media using Darcy law. The equations are as follows:

.U=0;
U=p;

where U is the velocity, p is pressure. is the viscosity and K is the permeability.

As the inlet velocity is considered a constant in the case of my problem, I decided to use fixedFluxPressure BC. So, the the initial and boundary conditions would be:

p:

internalField   uniform 0;

boundaryField
{
    inlet
    {
        type            fixedFluxPressure;
    }

    outlet
    {
        type            fixedValue;
        value           uniform 0;
    }

    frontAndBackAndTopAndBottom
    {
        type            empty;
    }
}

and U:

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform (1 0 0);
    }

    outlet
    {
        type            zeroGradient
    }

    frontAndBackAndTopAndBottom
    {
        type            empty;
    }
}

I tried to solve the equations as follows:

fvScalarMatrix pEqn
    (
	fvm::laplacian(k/mu,p)
    );
pEqn.solve();

U=-k/mu*fvc::grad(p);

However, when I run my solver the case, I get this error:

--> FOAM FATAL ERROR:
updateCoeffs(const scalarField& snGradp) MUST be called before updateCoeffs() or evaluate() to set the boundary gradient.

    From function virtual void Foam::fixedFluxPressureFvPatchScalarField::updateCoeffs()
    in file fields/fvPatchFields/derived/fixedFluxPressure/fixedFluxPressureFvPatchScalarField.C at line 157.

I don't know exactly how this fixedFluxPressure BC works and How it exactly uses the velocity field to calculate pressure gradient at the inlet. I would be very appreciated if anyone can help me with this.

[Kenmaster]

Originally Posted by MCrossover97

Hey everybody!

I want to simulate 1D steady state flow in porous media using Darcy law. The equations are as follows:

.U=0;
U=p;

where U is the velocity, p is pressure. is the viscosity and K is the permeability.

As the inlet velocity is considered a constant in the case of my problem, I decided to use fixedFluxPressure BC. So, the the initial and boundary conditions would be:

p:

internalField   uniform 0;

boundaryField
{
    inlet
    {
        type            fixedFluxPressure;
    }

    outlet
    {
        type            fixedValue;
        value           uniform 0;
    }

    frontAndBackAndTopAndBottom
    {
        type            empty;
    }
}

and U:

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform (1 0 0);
    }

    outlet
    {
        type            zeroGradient
    }

    frontAndBackAndTopAndBottom
    {
        type            empty;
    }
}

I tried to solve the equations as follows:

fvScalarMatrix pEqn
    (
	fvm::laplacian(k/mu,p)
    );
pEqn.solve();

U=-k/mu*fvc::grad(p);

However, when I run my solver the case, I get this error:

--> FOAM FATAL ERROR:
updateCoeffs(const scalarField& snGradp) MUST be called before updateCoeffs() or evaluate() to set the boundary gradient.

    From function virtual void Foam::fixedFluxPressureFvPatchScalarField::updateCoeffs()
    in file fields/fvPatchFields/derived/fixedFluxPressure/fixedFluxPressureFvPatchScalarField.C at line 157.

I don't know exactly how this fixedFluxPressure BC works and How it exactly uses the velocity field to calculate pressure gradient at the inlet. I would be very appreciated if anyone can help me with this.

Did you solve this