solvers_porousScalarTransport2DFoam

porousScalarTransport2DFoam solver

Description

Solves the transport equation of a passive scalar for free-surface flow in porous media with dispersion coefficient model.

The transport is implicitly solved and based on pre-computed flux phi or velocity U field and water depth hwater

Configuration files

constant/transportProperties :

eps eps [0 0 0 0 0 0 0] 0.25; // porosity (can be volScalarField in constant/)

Dm Dm [0 2 -1 0 0 0 0] 1e-9; // molecular diffusion

porousTransport // specific dictionary for transport
{
  phaseName a; // to specify the flux field (phia here) or velocity field (Ua)
  Kd Kd [-1 3 0 0 0 0 0] 1e-3;
  rs rs [1 -3 0 0 0 0 0] 1000;
  epsTotal epsTotal [0 0 0 0 0 0 0] 0.30;
  lambda lambda [0 0 -1 0 0 0 0 ] 0;// decay of the C scalar
}

dispersionModel alphaDispersion; // dispersion model

alphaDispersionCoeffs
{
  tau tau [0 0 0 0 0 0 0] 2; // tortuosity
  alphaL alphaL [0 1 0 0 0 0 0] 0.01; // longitudinal dispersivity
  alphaT alphaT [0 1 0 0 0 0 0] 0.002; // transverse dispersivity
}

eventFileTracerSource injectionFile.dat;  // to specify event file for time-dependent source term

system/controlDict :

adjustTimeStep yes;

truncationError 0.001; // Allowed time-scheme truncation error used to manage time-step

CSVoutput       true; // active the CmassBalance.csv output

eventTimeTracking true; // to force the solver to compute solutions at each event time (patch/source/output)

Required fields

• 0/C : The concentration field
• 0/phia : The pre-computed flux field where a can be changed in porousTransport dictionary (can be computed using 0/Ua)
• 0/hwater : The pre-computed water depth

Optional fields

• 0/Ua : Used to compute 0/phia if not present
• Other spatially defined parameters : alphaL , alphaT, eps

Timestep managing

The computation of timestep for next iteration is directly computed using truncation error related to the time scheme defined (Euler, backward, CrankNicolson). The time step formula for backward time-scheme is for example :

deltaT = Foam::pow(3 x truncationError x Cmax[speciesi]/dC3dT3max[speciesi],1./3.)

where dC3dT3maxmaximal is the maximal value of the thid time derivative and Cmax the value of C in this cell.

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