RelPermNonWettingPhaseVanGenuchtenMualem.cpp

Go to the documentation of this file.

// SPDX-FileCopyrightText: Copyright (c) OpenGeoSys Community (opengeosys.org)
// SPDX-License-Identifier: BSD-3-Clause
 
#include "RelPermNonWettingPhaseVanGenuchtenMualem.h"
 
#include <algorithm>
#include <cmath>
#include <limits>
 
#include "BaseLib/Error.h"
#include "MaterialLib/MPL/Medium.h"
#include "MaterialLib/MPL/Utils/CheckVanGenuchtenExponentRange.h"
#include "MathLib/Nonlinear/Root1D.h"
 
namespace MaterialPropertyLib
{
double computeVanGenuchtenMualemValue(const double S_L, const double S_L_r,
                                      const double S_L_max, const double m)
{
    const double Se = (S_L - S_L_r) / (S_L_max - S_L_r);
    return std::sqrt(1.0 - Se) * std::pow(1.0 - std::pow(Se, 1.0 / m), 2.0 * m);
}
 
RelPermNonWettingPhaseVanGenuchtenMualem::
    RelPermNonWettingPhaseVanGenuchtenMualem(std::string name,
                                             const double S_L_r,
                                             const double S_n_r,
                                             const double m,
                                             const double krel_min,
                                             const double a)
    : S_L_r_(S_L_r),
      S_L_max_(1. - S_n_r),
      m_(m),
      krel_min_(krel_min),
      S_L_for_krel_min_(computeSaturationForMinimumRelativePermeability()),
      a_(a)
{
    name_ = std::move(name);
    checkVanGenuchtenExponentRange(m_);
}
 
PropertyDataType RelPermNonWettingPhaseVanGenuchtenMualem::value(
    VariableArray const& variable_array,
    ParameterLib::SpatialPosition const& /*pos*/, double const /*t*/,
    double const /*dt*/) const
{
    const double S_L =
        std::clamp(variable_array.liquid_saturation, S_L_r_, S_L_max_);
 
    const double krel =
        computeVanGenuchtenMualemValue(S_L, S_L_r_, S_L_max_, m_);
    return std::max(krel_min_, a_ * krel);
}
 
PropertyDataType RelPermNonWettingPhaseVanGenuchtenMualem::dValue(
    VariableArray const& variable_array, Variable const variable,
    ParameterLib::SpatialPosition const& /*pos*/, double const /*t*/,
    double const /*dt*/) const
{
    if (variable != Variable::liquid_saturation)
    {
        OGS_FATAL(
            "RelPermNonWettingPhaseVanGenuchtenMualem::dValue is implemented "
            "for the derivative with respect to liquid saturation only.");
    }
 
    const double S_L = variable_array.liquid_saturation;
    if (S_L < S_L_r_ || S_L > S_L_for_krel_min_)
    {
        return 0.0;
    }
 
    if (std::fabs(S_L - S_L_max_) < std::numeric_limits<double>::epsilon())
    {
        return 0.0;
    }
 
    const double Se = (S_L - S_L_r_) / (S_L_max_ - S_L_r_);
 
    const double val1 = std::sqrt(1.0 - Se);
    const double val2 = 1.0 - std::pow(Se, 1.0 / m_);
 
    return a_ *
           (-0.5 * std::pow(val2, 2.0 * m_) / val1 -
            2.0 * std::pow(Se, -1.0 + 1.0 / m_) * val1 *
                std::pow(val2, 2.0 * m_ - 1.0)) /
           (S_L_max_ - S_L_r_);
}
 
double RelPermNonWettingPhaseVanGenuchtenMualem::
    computeSaturationForMinimumRelativePermeability() const
{
    auto f = [this](double S_L) -> double
    {
        return computeVanGenuchtenMualemValue(S_L, this->S_L_r_, this->S_L_max_,
                                              this->m_) -
               this->krel_min_;
    };
 
    auto root_finder =
        MathLib::Nonlinear::makeRegulaFalsi<MathLib::Nonlinear::Pegasus>(
            f, S_L_r_, S_L_max_);
 
    root_finder.step(1000);
 
    return root_finder.getResult();
}
}  // namespace MaterialPropertyLib