[Jose Manuel Olmos]

Hello everyone,

I'm trying to simulate the flow of a solution (containing a solute) inside a pipe. I'm using the icoFoam solver with some modifications on the code for including the transport of the solute (just after calculating the distribution of velocities):

[I]fvVectorMatrix UEqn
(
fvm::ddt(U)
+ fvm::div(phi, U)
- fvm::laplacian(nu, U)
);

if (piso.momentumPredictor())
{
solve(UEqn == -fvc::grad(p));
}

// --- PISO loop
while (piso.correct())
{
volScalarField rAU(1.0/UEqn.A());
volVectorField HbyA(constrainHbyA(rAU*UEqn.H(), U, p));
surfaceScalarField phiHbyA
(
"phiHbyA",
fvc::flux(HbyA)
+ fvc::interpolate(rAU)*fvc::ddtCorr(U, phi)
);
adjustPhi(phiHbyA, U, p);
// Update the pressure BCs to ensure flux consistency
constrainPressure(p, U, phiHbyA, rAU);

// Non-orthogonal pressure corrector loop
while (piso.correctNonOrthogonal())
{
// Pressure corrector
fvScalarMatrix pEqn
(
fvm::laplacian(rAU, p) == fvc::div(phiHbyA)
);
pEqn.setReference(pRefCell, pRefValue);
pEqn.solve();

if (piso.finalNonOrthogonalIter())
{
phi = phiHbyA - pEqn.flux();
}
}
#include "continuityErrs.H"
U = HbyA - rAU*fvc::grad(p);
U.correctBoundaryConditions();
}
// --- Mass transport

dictionary soluteSolveDict = mesh.solutionDict().subDict("solvers").subDict("C_ solutes");
forAll(soluteNameList, i)
{
fvScalarMatrix MassTransport
(
fvm::ddt(soluteList[i]) + fvm::div(phi, soluteList[i], "div(phi,C_solutes)")
- fvm::laplacian(soluteList[i].D(), soluteList, "laplacian(D,C_solutes)")
);
MassTransport.solve(soluteSolveDict);
}

// --- Write run time

The solver is running and the distribution of concentrations is calculated. However, it only takes part from the inlet of the pipe.. I mean, the transport of the momentum and the concentration of the solute is not "synchronized. You can see this problem in the following images, that show the distribution of velocities and concentrations at the same time:

https://ibb.co/bQLCf2v
https://ibb.co/7XSj25K

Before running the simulation, I created a new field ("concentration") with the following boundary conditions:

dimensions [0 -3 0 0 1 0 0];

internalField uniform 0;

boundaryField
{
CAD_inlet
{
type fixedValue;
value uniform 0.01; //this is the concentration of the solute at
//the inlet
}

CAD_outlet
{
type zeroGradient;
}

CAD_wall
{
type zeroGradient;
}
}

I don't understand why the solution reach the outlet of the pipe (the velocity is non-null at this zone) but the solute is only at the first of the pipe. I would be very grateful if anyone could tell me if I'm taking any mistake on the modification of the solver or in the establishment of the boundary conditions.

Thanks in advance,
Jose Manuel