OGS
gas_flow.prj
<OpenGeoSysProject>
  <meshes>
    <mesh>square_1x1_quad8_1e2.vtu</mesh>
    <mesh>square_1x1_geometry_left.vtu</mesh>
  </meshes>
  <processes>
    <process>
      <name>LF_GAS</name>
      <type>LIQUID_FLOW</type>
      <integration_order>3</integration_order>
      <equation_balance_type>mass</equation_balance_type>
      <process_variables>
        <process_variable>pressure</process_variable>
      </process_variables>
      <secondary_variables>
        <secondary_variable internal_name="darcy_velocity" output_name="v" />
      </secondary_variables>
      <specific_body_force>0 0</specific_body_force>
    </process>
  </processes>
  <media>
    <medium>
      <phases>
        <phase>
          <type>Gas</type>
          <properties>
            <property>
              <name>viscosity</name>
              <type>Constant</type>
              <value>1e-5</value>
            </property>
            <property>
              <name>density</name>
              <type>IdealGasLaw</type>
            </property>
            <property>
              <name>molar_mass</name>
              <type>Constant</type>
              <value>0.028964397787206768</value>
            </property>
          </properties>
        </phase>
        <phase>
          <type>Solid</type>
          <properties>
            <property>
              <name>density</name>
              <type>Constant</type>
              <value>2.17e3</value>
            </property>
          </properties>
        </phase>
      </phases>
      <properties>
        <property>
          <name>porosity</name>
          <type>Constant</type>
          <value>0.03</value>
        </property>
        <property>
          <name>reference_temperature</name>
          <type>Constant</type>
          <value>293.15</value>
        </property>
        <property>
          <name>permeability</name>
          <type>Constant</type>
          <value>1e-4</value>
        </property>
        <property>
          <name>storage</name>
          <type>Constant</type>
          <value>0.0</value>
        </property>
      </properties>
    </medium>
  </media>
  <time_loop>
    <processes>
      <process ref="LF_GAS">
        <nonlinear_solver>basic_picard</nonlinear_solver>
        <convergence_criterion>
          <type>DeltaX</type>
          <norm_type>NORM2</norm_type>
          <reltol>1.e-6</reltol>
        </convergence_criterion>
        <time_discretization>
          <type>BackwardEuler</type>
        </time_discretization>
        <time_stepping>
          <type>FixedTimeStepping</type>
          <t_initial>0</t_initial>
          <t_end>100</t_end>
          <timesteps>
            <pair>
              <repeat>1</repeat>
              <delta_t>0.1</delta_t>
            </pair>
          </timesteps>
        </time_stepping>
      </process>
    </processes>
    <output>
      <type>VTK</type>
      <prefix>gas_flow</prefix>
      <timesteps>
        <pair>
          <repeat>1</repeat>
          <each_steps>1000</each_steps>
        </pair>
      </timesteps>
      <variables>
        <variable>pressure</variable>
        <variable>velocity</variable>
      </variables>
      <suffix>ts{:timestep}_t_{:time}</suffix>
    </output>
  </time_loop>
  <parameters>
    <parameter>
      <name>pressure0</name>
      <type>Constant</type>
      <values>1e5</values>
    </parameter>
    <parameter>
      <name>zero</name>
      <type>Constant</type>
      <value>0</value>
    </parameter>
    <parameter>
      <name>flux</name>
      <type>Constant</type>
      <value>1e-3</value>
    </parameter>
  </parameters>
  <process_variables>
    <process_variable>
      <name>pressure</name>
      <components>1</components>
      <order>2</order>
      <initial_condition>pressure0</initial_condition>
      <boundary_conditions>
        <boundary_condition>
          <mesh>square_1x1_geometry_left</mesh>
          <type>Neumann</type>
          <parameter>flux</parameter>
        </boundary_condition>
      </boundary_conditions>
    </process_variable>
  </process_variables>
  <nonlinear_solvers>
    <nonlinear_solver>
      <name>basic_picard</name>
      <type>Picard</type>
      <max_iter>100</max_iter>
      <linear_solver>general_linear_solver</linear_solver>
    </nonlinear_solver>
  </nonlinear_solvers>
  <linear_solvers>
    <linear_solver>
      <name>general_linear_solver</name>
      <lis>-i bicgstab -p ilu -tol 1e-16 -maxiter 10000</lis>
      <eigen>
        <solver_type>BiCGSTAB</solver_type>
        <precon_type>ILUT</precon_type>
        <max_iteration_step>3000</max_iteration_step>
        <error_tolerance>1e-18</error_tolerance>
      </eigen>
    </linear_solver>
  </linear_solvers>
</OpenGeoSysProject>