Merge pull request #6005 from bobmyhill/fix_cvp

fix damper stress calculation

source/material_model/rheology/composite_visco_plastic.cc

@@ -343,7 +343,7 @@ namespace aspect
         // arranged in parallel with the viscoplastic elements.
         // The total stress is equal to the sum of the viscoplastic stress and
         // minimum stress.
-        const double damper_stress = 2. * damper_viscosity * edot_ii;
+        const double damper_stress = 2. * damper_viscosity * (edot_ii - partial_strain_rates[4]);
         const double total_stress = viscoplastic_stress + damper_stress;
 
         // 6) Return the effective creep viscosity using the total stress
@@ -600,7 +600,7 @@ namespace aspect
         // arranged in parallel with the viscoplastic elements.
         // The total stress is equal to the sum of the viscoplastic stress and
         // minimum stress.
-        const double damper_stress = 2. * damper_viscosity * edot_ii;
+        const double damper_stress = 2. * damper_viscosity * (edot_ii - partial_strain_rates[4]);
         const double total_stress = viscoplastic_stress + damper_stress;
 
         // 6) Return the effective creep viscosity using the total stress
@@ -772,6 +772,15 @@ namespace aspect
         // eta_max / (eta_max - eta_min) becomes a useful value,
         // which we here call the "strain_rate_scaling_factor".
         const double minimum_viscosity = prm.get_double("Minimum viscosity");
+
+        AssertThrow(minimum_viscosity > 0,
+                    ExcMessage("Minimum viscosity needs to be larger than zero."));
+
+        AssertThrow(maximum_viscosity > 1.1 * minimum_viscosity,
+                    ExcMessage("The maximum viscosity needs to be at least ten percent larger than the minimum viscosity. "
+                               "If you require an isoviscous model consider a different rheology, or set the "
+                               "parameters of the active flow laws to be independent of temperature, pressure, grain size, and stress."));
+
         strain_rate_scaling_factor = maximum_viscosity / (maximum_viscosity - minimum_viscosity);
         damper_viscosity = maximum_viscosity * minimum_viscosity / (maximum_viscosity - minimum_viscosity);
 

tests/composite_viscous_outputs_limited.cc

@@ -0,0 +1,222 @@
+/*
+  Copyright (C) 2022 - 2023 by the authors of the ASPECT code.
+
+  This file is part of ASPECT.
+
+  ASPECT 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 2, or (at your option)
+  any later version.
+
+  ASPECT is distributed in the hope that it will be useful,
+  but WITHOUT ANY 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 ASPECT; see the file LICENSE.  If not see
+  <http://www.gnu.org/licenses/>.
+*/
+
+#include <aspect/simulator.h>
+#include <aspect/material_model/rheology/composite_visco_plastic.h>
+#include <aspect/simulator_signals.h>
+
+template <int dim>
+void f(const aspect::SimulatorAccess<dim> &simulator_access,
+       aspect::Assemblers::Manager<dim> &)
+{
+  // This function tests whether the composite creep rheology is producing
+  // the correct composite viscosity and partial strain rates corresponding to
+  // the different creep mechanisms incorporated into the rheology.
+  // It is assumed that each individual creep mechanism has already been tested.
+
+  using namespace aspect::MaterialModel;
+
+  // First, we set up a few objects which are used by the rheology model.
+  aspect::ParameterHandler prm;
+  const std::vector<std::string> list_of_composition_names = simulator_access.introspection().get_composition_names();
+  auto n_phases = std::make_unique<std::vector<unsigned int>>(1); // 1 phase per composition
+  const unsigned int composition = 0;
+  const std::vector<double> volume_fractions = {1.};
+  const std::vector<double> phase_function_values = std::vector<double>();
+  const std::vector<unsigned int> n_phase_transitions_per_composition = std::vector<unsigned int>(1);
+
+  // Next, we initialise instances of the composite rheology and
+  // individual creep mechanisms.
+  std::unique_ptr<Rheology::CompositeViscoPlastic<dim>> composite_creep;
+  composite_creep = std::make_unique<Rheology::CompositeViscoPlastic<dim>>();
+  composite_creep->initialize_simulator (simulator_access.get_simulator());
+  composite_creep->declare_parameters(prm);
+  prm.set("Viscosity averaging scheme", "isostrain");
+  prm.set("Include diffusion creep in composite rheology", "true");
+  prm.set("Include dislocation creep in composite rheology", "true");
+  prm.set("Include Peierls creep in composite rheology", "true");
+  prm.set("Include Drucker Prager plasticity in composite rheology", "true");
+  prm.set("Peierls creep flow law", "viscosity approximation");
+  prm.set("Maximum yield stress", "5e8");
+  prm.set("Minimum viscosity", "1e18");
+  prm.set("Maximum viscosity", "4e18");
+  composite_creep->parse_parameters(prm);
+
+  std::unique_ptr<Rheology::DiffusionCreep<dim>> diffusion_creep;
+  diffusion_creep = std::make_unique<Rheology::DiffusionCreep<dim>>();
+  diffusion_creep->initialize_simulator (simulator_access.get_simulator());
+  diffusion_creep->declare_parameters(prm);
+  diffusion_creep->parse_parameters(prm);
+
+  std::unique_ptr<Rheology::DislocationCreep<dim>> dislocation_creep;
+  dislocation_creep = std::make_unique<Rheology::DislocationCreep<dim>>();
+  dislocation_creep->initialize_simulator (simulator_access.get_simulator());
+  dislocation_creep->declare_parameters(prm);
+  dislocation_creep->parse_parameters(prm);
+
+  std::unique_ptr<Rheology::PeierlsCreep<dim>> peierls_creep;
+  peierls_creep = std::make_unique<Rheology::PeierlsCreep<dim>>();
+  peierls_creep->initialize_simulator (simulator_access.get_simulator());
+  peierls_creep->declare_parameters(prm);
+  peierls_creep->parse_parameters(prm);
+
+  std::unique_ptr<Rheology::DruckerPragerPower<dim>> drucker_prager_power;
+  drucker_prager_power = std::make_unique<Rheology::DruckerPragerPower<dim>>();
+  drucker_prager_power->initialize_simulator (simulator_access.get_simulator());
+  drucker_prager_power->declare_parameters(prm);
+  prm.set("Maximum yield stress", "5e8");
+  drucker_prager_power->parse_parameters(prm);
+  Rheology::DruckerPragerParameters p = drucker_prager_power->compute_drucker_prager_parameters(composition, phase_function_values, n_phase_transitions_per_composition);
+
+  // The creep components are arranged in series with each other.
+  // This package of components is then arranged in parallel with
+  // a strain rate limiter with a constant viscosity lim_visc.
+  // The whole system is then arranged in series with a viscosity limiter with
+  // viscosity maximum_viscosity.
+  // lim_visc is equal to (minimum_viscosity*maximum_viscosity)/(maximum_viscosity - minimum_viscosity)
+  double minimum_viscosity = prm.get_double("Minimum viscosity");
+  double maximum_viscosity = prm.get_double("Maximum viscosity");
+
+  AssertThrow(minimum_viscosity > 0,
+              ExcMessage("Minimum viscosity needs to be larger than zero."));
+
+  AssertThrow(maximum_viscosity > 1.1 * minimum_viscosity,
+              ExcMessage("The maximum viscosity needs to be at least ten percent larger than the minimum viscosity. "
+                         "If you require an isoviscous model consider a different rheology, or set the "
+                         "parameters of the active flow laws to be independent of temperature, pressure, grain size, and stress."));
+
+  double lim_visc = (minimum_viscosity*maximum_viscosity)/(maximum_viscosity - minimum_viscosity);
+
+  // Assign values to the variables which will be passed to compute_viscosity
+  // The test involves pure shear calculations at 1 GPa and variable temperature
+  double temperature;
+  const double pressure = 1.e9;
+  const double grain_size = 1.e-3;
+  SymmetricTensor<2,dim> strain_rate;
+  strain_rate[0][0] = -1e-11;
+  strain_rate[0][1] = 0.;
+  strain_rate[1][1] = 1e-11;
+  strain_rate[2][0] = 0.;
+  strain_rate[2][1] = 0.;
+  strain_rate[2][2] = 0.;
+
+  std::cout << "temperature (K)   eta (Pas)   creep stress (Pa)   edot_ii (/s)   edot_ii fractions (diff, disl, prls, drpr, max)" << std::endl;
+
+  // Loop through strain rates, tracking whether there is a discrepancy in
+  // the decomposed strain rates.
+  bool error = false;
+  double viscosity;
+  double total_strain_rate;
+  double creep_strain_rate;
+  double creep_stress;
+  double diff_stress;
+  double disl_stress;
+  double prls_stress;
+  double drpr_stress;
+  std::vector<double> partial_strain_rates(5, 0.);
+
+  for (unsigned int i=0; i <= 10; i++)
+    {
+      temperature = 1000. + i*100.;
+
+      // Compute the viscosity
+      viscosity = composite_creep->compute_viscosity(pressure, temperature, grain_size, volume_fractions, strain_rate, partial_strain_rates);
+      total_strain_rate = std::accumulate(partial_strain_rates.begin(), partial_strain_rates.end(), 0.);
+
+      // The creep strain rate is calculated by subtracting the strain rate
+      // of the max viscosity dashpot from the total strain rate
+      // The creep stress is then calculated by subtracting the stress running
+      // through the strain rate limiter from the total stress
+      creep_strain_rate = total_strain_rate - partial_strain_rates[4];
+      creep_stress = 2.*(viscosity*total_strain_rate - lim_visc*creep_strain_rate);
+
+      // Print the output
+      std::cout << temperature << ' ' << viscosity << ' ' << creep_stress << ' ' << total_strain_rate;
+      for (unsigned int i=0; i < partial_strain_rates.size(); ++i)
+        {
+          std::cout << ' ' << partial_strain_rates[i]/total_strain_rate;
+        }
+      std::cout << std::endl;
+
+      // The following lines test that each individual creep mechanism
+      // experiences the same creep stress
+
+      // Each creep mechanism should experience the same stress
+      diff_stress = 2.*partial_strain_rates[0]*diffusion_creep->compute_viscosity(pressure, temperature, grain_size, composition);
+      disl_stress = 2.*partial_strain_rates[1]*dislocation_creep->compute_viscosity(partial_strain_rates[1], pressure, temperature, composition);
+      prls_stress = 2.*partial_strain_rates[2]*peierls_creep->compute_viscosity(partial_strain_rates[2], pressure, temperature, composition);
+      if (partial_strain_rates[3] > 0.)
+        {
+          drpr_stress = 2.*partial_strain_rates[3]*drucker_prager_power->compute_viscosity(p.cohesion,
+                        p.angle_internal_friction,
+                        pressure,
+                        partial_strain_rates[3],
+                        p.max_yield_stress);
+        }
+      else
+        {
+          drpr_stress = creep_stress;
+        }
+
+      if ((std::fabs((diff_stress - creep_stress)/creep_stress) > 1e-6)
+          || (std::fabs((disl_stress - creep_stress)/creep_stress) > 1e-6)
+          || (std::fabs((prls_stress - creep_stress)/creep_stress) > 1e-6)
+          || (std::fabs((drpr_stress - creep_stress)/creep_stress) > 1e-6))
+        {
+          error = true;
+          std::cout << "   creep stress: " << creep_stress;
+          std::cout << " diffusion stress: " << diff_stress;
+          std::cout << " dislocation stress: " << disl_stress;
+          std::cout << " peierls stress: " << prls_stress;
+          std::cout << " drucker prager stress: " << drpr_stress << std::endl;
+        }
+    }
+
+  if (error)
+    {
+      std::cout << "   Error: The individual creep stresses differ by more than the required tolerance." << std::endl;
+      std::cout << "Some parts of the test were not successful." << std::endl;
+    }
+  else
+    {
+      std::cout << "OK" << std::endl;
+    }
+
+}
+
+template <>
+void f(const aspect::SimulatorAccess<2> &,
+       aspect::Assemblers::Manager<2> &)
+{
+  AssertThrow(false,dealii::ExcInternalError());
+}
+
+template <int dim>
+void signal_connector (aspect::SimulatorSignals<dim> &signals)
+{
+  using namespace dealii;
+  std::cout << "* Connecting signals" << std::endl;
+  signals.set_assemblers.connect (std::bind(&f<dim>,
+                                            std::placeholders::_1,
+                                            std::placeholders::_2));
+}
+
+ASPECT_REGISTER_SIGNALS_CONNECTOR(signal_connector<2>,
+                                  signal_connector<3>)

tests/composite_viscous_outputs_limited.prm

@@ -0,0 +1,84 @@
+# This test is a modification of the composite_viscous_outputs test
+# that adds a minimum and maximum viscosity limiter with values
+# that are somewhat close. It documents the behavior of the rheology
+# for this case, which is that when the maximum viscosity (here 4e18)
+# approaches the minimum viscosity (1e18) the effective maximum and
+# minimum viscosities are different from the ones prescribed in
+# the input file (1.33e18 and 5.33e18 in this test).
+
+set Additional shared libraries = tests/libcomposite_viscous_outputs.so
+set Dimension                              = 3
+set End time                               = 0
+set Use years in output instead of seconds = true
+set Nonlinear solver scheme                = no Advection, no Stokes
+
+# Model geometry (100x100 km, 10 km spacing)
+subsection Geometry model
+  set Model name = box
+
+  subsection Box
+    set X repetitions = 10
+    set Y repetitions = 10
+    set X extent      = 100e3
+    set Y extent      = 100e3
+  end
+end
+
+# Mesh refinement specifications
+subsection Mesh refinement
+  set Initial adaptive refinement        = 0
+  set Initial global refinement          = 0
+  set Time steps between mesh refinement = 0
+end
+
+# Boundary classifications (fixed T boundaries, prescribed velocity)
+
+# Temperature boundary and initial conditions
+subsection Boundary temperature model
+  set Fixed temperature boundary indicators   = bottom, top, left, right
+  set List of model names = box
+
+  subsection Box
+    set Bottom temperature = 273
+    set Left temperature   = 273
+    set Right temperature  = 273
+    set Top temperature    = 273
+  end
+end
+
+# Velocity on boundaries characterized by functions
+subsection Boundary velocity model
+  set Prescribed velocity boundary indicators = bottom y: function, top y: function, left x: function, right x: function
+
+  subsection Function
+    set Variable names      = x,y,z
+    set Function constants  = m=0.0005, year=1
+    set Function expression = if (x<50e3 , -1*m/year, 1*m/year); if (y<50e3 , 1*m/year, -1*m/year);0
+  end
+end
+
+subsection Initial temperature model
+  set Model name = function
+
+  subsection Function
+    set Function expression = 273
+  end
+end
+
+# Material model
+subsection Material model
+  set Model name = visco plastic
+
+  subsection Visco Plastic
+    set Angles of internal friction = 30.
+  end
+end
+
+# Gravity model
+subsection Gravity model
+  set Model name = vertical
+
+  subsection Vertical
+    set Magnitude = 10.0
+  end
+end

tests/composite_viscous_outputs_limited/screen-output

@@ -0,0 +1,28 @@
+
+Loading shared library <./libcomposite_viscous_outputs_limited.debug.so>
+
+* Connecting signals
+temperature (K)   eta (Pas)   creep stress (Pa)   edot_ii (/s)   edot_ii fractions (diff, disl, prls, drpr, max)
+1000 3.99999e+18 7.99998e+07 1e-11 1.5072e-07 1.93692e-06 1.58471e-11 1.60671e-47 0.999998
+1100 3.997e+18 7.99201e+07 1e-11 9.7033e-06 0.000739244 7.95399e-10 1.52864e-47 0.999251
+1200 3.70523e+18 7.21395e+07 1e-11 0.000281896 0.0734102 8.42438e-09 9.12346e-50 0.926308
+1300 2.33707e+18 3.56552e+07 1e-11 0.00262872 0.413104 3.88781e-10 4.546e-65 0.584267
+1400 1.5335e+18 1.42267e+07 1e-11 0.0130073 0.603618 4.18203e-12 5.08959e-85 0.383375
+1500 1.22332e+18 5.95532e+06 1e-11 0.0482676 0.645901 9.24051e-14 6.26253e-104 0.305831
+1600 1.09939e+18 2.65043e+06 1e-11 0.144969 0.580183 4.10546e-15 1.64922e-121 0.274848
+1700 1.04457e+18 1.1886e+06 1e-11 0.350471 0.388386 2.29166e-16 6.35863e-139 0.261143
+1800 1.01759e+18 469097 1e-11 0.618354 0.127248 6.34559e-18 4.11763e-159 0.254398
+1900 1.00547e+18 145858 1e-11 0.734184 0.0144489 4.62654e-20 1.77001e-184 0.251367
+2000 1.00167e+18 44514.1 1e-11 0.748313 0.00126937 3.89551e-22 2.99484e-210 0.250417
+OK
+Number of active cells: 100 (on 1 levels)
+Number of degrees of freedom: 5,534 (3,969+242+1,323)
+
+*** Timestep 0:  t=0 years, dt=0 years
+
+   Postprocessing:
+
+Termination requested by criterion: end time
+
+
+