ThermoDiffusion.C

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//* This file is part of the MOOSE framework
//* https://mooseframework.inl.gov
//*
//* All rights reserved, see COPYRIGHT for full restrictions
//* https://github.com/idaholab/moose/blob/master/COPYRIGHT
//*
//* Licensed under LGPL 2.1, please see LICENSE for details
//* https://www.gnu.org/licenses/lgpl-2.1.html
 
#include "ThermoDiffusion.h"
 
registerMooseObject("MiscApp", ThermoDiffusion);
 
InputParameters
ThermoDiffusion::validParams()
{
  InputParameters params = Kernel::validParams();
  params.addRequiredCoupledVar("temp", "Coupled temperature");
  params.addParam<Real>("gas_constant", 8.3144621, "Gas constant");
  params.addParam<std::string>(
      "heat_of_transport", "heat_of_transport", "Property name for the heat of transport.");
  params.addParam<std::string>(
      "mass_diffusivity", "mass_diffusivity", "Property name for the diffusivity.");
 
  params.addClassDescription("Kernel for thermo-diffusion (Soret effect, thermophoresis, etc.)");
  return params;
}
 
ThermoDiffusion::ThermoDiffusion(const InputParameters & parameters)
  : Kernel(parameters),
    _temperature(coupledValue("temp")),
    _grad_temperature(coupledGradient("temp")),
    _mass_diffusivity(getMaterialProperty<Real>(getParam<std::string>("mass_diffusivity"))),
    _heat_of_transport(getMaterialProperty<Real>(getParam<std::string>("heat_of_transport"))),
    _gas_constant(getParam<Real>("gas_constant")),
    _temperature_index(coupled("temp"))
{
}
 
RealGradient
ThermoDiffusion::thermoDiffusionVelocity() const
{
  // The thermo-diffusion term looks like grad( v * C ) where v is like a diffusive
  // velocity. If the concentration C does not couple back into the heat equation,
  // then the one-way coupling of temperature means that thermo-diffusion of C
  // behaves like advection. Then v is the velocity:
  //
  //   v = D Qstar grad(T) / ( R T^2 )
  //
  Real coeff = _mass_diffusivity[_qp] * _heat_of_transport[_qp] /
               (_gas_constant * _temperature[_qp] * _temperature[_qp]);
  return coeff * _grad_temperature[_qp];
}
 
Real
ThermoDiffusion::computeQpResidual()
{
  return thermoDiffusionVelocity() * _u[_qp] * _grad_test[_i][_qp];
}
 
Real
ThermoDiffusion::computeQpJacobian()
{
  return thermoDiffusionVelocity() * _phi[_j][_qp] * _grad_test[_i][_qp];
}
 
Real
ThermoDiffusion::computeQpOffDiagJacobian(unsigned int jvar)
{
  if (jvar == _temperature_index)
  {
    Real coeff = _mass_diffusivity[_qp] * _heat_of_transport[_qp] /
                 (_gas_constant * _temperature[_qp] * _temperature[_qp]);
    return coeff * _grad_test[_i][_qp] * _u[_qp] *
           (_grad_phi[_j][_qp] - 2 * _phi[_j][_qp] * _grad_temperature[_qp] / _temperature[_qp]);
  }
  return 0;
}