PatersonBuddCold.cc

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/* Copyright (C) 2015, 2016, 2018, 2023, 2025 PISM Authors
 *
 * This file is part of PISM.
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 * PISM is free software; you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 3 of the License, or (at your option) any later
 * version.
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 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with PISM; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
 
#include <cmath>
 
#include "pism/rheology/PatersonBuddCold.hh"
#include "pism/util/Config.hh"
 
namespace pism {
namespace rheology {
 
PatersonBuddCold::PatersonBuddCold(double exponent,
                                   const Config &config,
                                   std::shared_ptr<EnthalpyConverter> ec)
  : PatersonBudd(exponent, config, ec) {
  m_name = "Paterson-Budd (cold case)";
}
 
double PatersonBuddCold::tempFromSoftness(double A) const {
  return - m_Q_cold / (m_ideal_gas_constant * (log(A) - log(m_A_cold)));
}
 
// takes care of hardness...
double PatersonBuddCold::softness_from_temp(double T_pa) const {
  return m_A_cold * exp(-m_Q_cold / (m_ideal_gas_constant * T_pa));
}
 
// ignores pressure and uses non-pressure-adjusted temperature
double PatersonBuddCold::flow_from_temp(double stress, double temp,
                                        double , double) const {
  return softness_from_temp(temp) * pow(stress,m_n-1);
}
 
 
// Rather than make this part of the base class, we just check at some reference values.
bool FlowLawIsPatersonBuddCold(const FlowLaw &flow_law, const Config &config,
                               std::shared_ptr<EnthalpyConverter> EC) {
  static const struct {
    double s, E, p, gs;
  } v[] = { { 1e3, 223, 1e6, 1e-3 },
            { 450000, 475000, 500000, 525000 },
            { 5e4, 268, 5e6, 3e-3 },
            { 1e5, 273, 8e6, 5e-3 } };
 
  double n = config.get_number("stress_balance.sia.Glen_exponent");
  PatersonBuddCold cpb(n, config, EC); // This is unmodified cold Paterson-Budd
 
  for (int i=0; i<4; i++) {
    const double left  = flow_law.flow(v[i].s, v[i].E, v[i].p, v[i].gs),
      right =  cpb.flow(v[i].s, v[i].E, v[i].p, v[i].gs);
    if (fabs((left - right)/left)>1.0e-15) {
      return false;
    }
  }
  return true;
}
 
} // end of namespace rheology
} // end of namespace pism