tGPBLD.cc - pism - [fork] customized build of PISM, the parallel ice sheet model (tillflux branch)
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       tGPBLD.cc (2695B)
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            1 /* Copyright (C) 2015, 2016, 2017, 2018 PISM Authors
            2  *
            3  * This file is part of PISM.
            4  *
            5  * PISM is free software; you can redistribute it and/or modify it under the
            6  * terms of the GNU General Public License as published by the Free Software
            7  * Foundation; either version 3 of the License, or (at your option) any later
            8  * version.
            9  *
           10  * PISM is distributed in the hope that it will be useful, but WITHOUT ANY
           11  * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
           12  * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
           13  * details.
           14  *
           15  * You should have received a copy of the GNU General Public License
           16  * along with PISM; if not, write to the Free Software
           17  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
           18  */
           19 
           20 #include "GPBLD.hh"
           21 #include "pism/util/ConfigInterface.hh"
           22 
           23 namespace pism {
           24 namespace rheology {
           25 
           26 /*!
           27   This constructor just sets flow law factor for nonzero water content, from
           28   \ref AschwandenBlatter and \ref LliboutryDuval1985.
           29 */
           30 GPBLD::GPBLD(const std::string &prefix,
           31              const Config &config, EnthalpyConverter::Ptr ec)
           32   : FlowLaw(prefix, config, ec) {
           33   m_name = "Glen-Paterson-Budd-Lliboutry-Duval";
           34 
           35   m_T_0              = config.get_number("constants.fresh_water.melting_point_temperature"); // K
           36   m_water_frac_coeff = config.get_number("flow_law.gpbld.water_frac_coeff");
           37 
           38   m_water_frac_observed_limit = config.get_number("flow_law.gpbld.water_frac_observed_limit");
           39 }
           40 
           41 //! The softness factor in the Glen-Paterson-Budd-Lliboutry-Duval flow law.  For constitutive law form.
           42 /*!
           43   This is a modification of Glen-Paterson-Budd ice, which is PatersonBudd.  In particular, if
           44   \f$A()\f$ is the softness factor for PatersonBudd, if \f$E\f$ is the enthalpy, and \f$p\f$ is
           45   the pressure then the softness we compute is
           46   \f[A = A(T_{pa}(E, p))(1+184\omega).\f]
           47   The pressure-melting temperature \f$T_{pa}(E, p)\f$ is computed by pressure_adjusted_temperature().
           48 */
           49 double GPBLD::softness_impl(double enthalpy, double pressure) const {
           50   const double E_s = m_EC->enthalpy_cts(pressure);
           51   if (enthalpy < E_s) {       // cold ice
           52     double T_pa = m_EC->pressure_adjusted_temperature(enthalpy, pressure);
           53     return softness_paterson_budd(T_pa);
           54   } else { // temperate ice
           55     double omega = m_EC->water_fraction(enthalpy, pressure);
           56     // as stated in \ref AschwandenBuelerBlatter, cap omega at max of observations:
           57     omega = std::min(omega, m_water_frac_observed_limit);
           58     // next line implements eqn (23) in \ref AschwandenBlatter2009
           59     return softness_paterson_budd(m_T_0) * (1.0 + m_water_frac_coeff * omega);
           60   }
           61 }
           62 
           63 } // end of namespace rheology
           64 } // end of namespace pism