WallDistanceMixingLengthAux.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 "WallDistanceMixingLengthAux.h"

registerMooseObject("NavierStokesApp", WallDistanceMixingLengthAux);

InputParameters
WallDistanceMixingLengthAux::validParams()
{
  InputParameters params = AuxKernel::validParams();
  params.addClassDescription(
      "Computes the turbulent mixing length by assuming that it is "
      "proportional to the distance from the nearest wall. The mixing"
      "length is capped at a distance proportional to inputted parameter delta.");
  params.addRequiredParam<std::vector<BoundaryName>>("walls",
                                                     "Boundaries that correspond to solid walls.");
  params.addParam<MooseFunctorName>("von_karman_const", 0.41, "");   // Von Karman constant
  params.addParam<MooseFunctorName>("von_karman_const_0", 0.09, ""); // Escudier' model parameter
  params.addParam<MooseFunctorName>(
      "delta",
      1e9,
      ""); // Tunable parameter related to the thickness of the boundary layer.
           // When it is not specified, Prandtl's original mixing length model is retrieved.
  return params;
}

WallDistanceMixingLengthAux::WallDistanceMixingLengthAux(const InputParameters & parameters)
  : AuxKernel(parameters),
    _wall_boundary_names(getParam<std::vector<BoundaryName>>("walls")),
    _von_karman_const(getFunctor<Real>("von_karman_const")),
    _von_karman_const_0(getFunctor<Real>("von_karman_const_0")),
    _delta(getFunctor<Real>("delta"))
{
  const MeshBase & mesh = _subproblem.mesh().getMesh();
  if (!mesh.is_replicated())
    mooseError("WallDistanceMixingLengthAux only supports replicated meshes");
  if (_var.feType() != FEType(CONSTANT, MONOMIAL))
    paramError("variable",
               "'",
               name(),
               "' computes the distance from the closest wall to an approximation of the element "
               "centroid; only a single dof is required to hold this value. Consequently users "
               "should always use a constant monomial finite element type (this is what finite "
               "volume variables implicitly use) for the auxiliary variables.");
}

Real
WallDistanceMixingLengthAux::computeValue()
{
  // Get reference to the libMesh mesh object
  const MeshBase & l_mesh = _mesh.getMesh();

  // Get the ids of the wall boundaries
  std::vector<BoundaryID> vec_ids = _mesh.getBoundaryIDs(_wall_boundary_names, true);

  // Loop over all boundaries
  Real min_dist2 = 1e9;
  const auto & bnd_to_elem_map = _mesh.getBoundariesToActiveSemiLocalElemIds();
  for (BoundaryID bid : vec_ids)
  {
    // Get the set of elements on this boundary
    auto search = bnd_to_elem_map.find(bid);
    if (search == bnd_to_elem_map.end())
      mooseError("Error computing wall distance; the boundary id ", bid, " is invalid");
    const auto & bnd_elems = search->second;

    // Loop over all boundary elements and find the distance to the closest one
    for (dof_id_type elem_id : bnd_elems)
    {
      const Elem & elem = l_mesh.elem_ref(elem_id);
      const auto side = _mesh.sideWithBoundaryID(&elem, bid);
      const auto bnd_pos = elem.side_ptr(side)->vertex_average();
      const auto distance = bnd_pos - _q_point[_qp];
      const auto dist2 = distance * distance;
      mooseAssert(dist2 != 0, "This distance should never be 0");
      min_dist2 = std::min(min_dist2, dist2);
    }
  }

  const Moose::ElemArg elem_arg = {_current_elem, false};
  const Moose::StateArg state_arg = Moose::currentState();

  const auto delta = _delta(elem_arg, state_arg);
  const auto von_karman_const = _von_karman_const(elem_arg, state_arg);
  const auto von_karman_const_0 = _von_karman_const_0(elem_arg, state_arg);

  if (std::sqrt(min_dist2) / delta <= von_karman_const_0 / von_karman_const)
    return von_karman_const * std::sqrt(min_dist2);
  else
    return von_karman_const_0 * delta;
}