 <OpenGeoSysProject>

   <meshes>

     <mesh>sphere.vtu</mesh>

     <mesh>geometry_top_point.vtu</mesh>

     <mesh>geometry_bottom_point.vtu</mesh>

   </meshes>

   <processes>

     <process>

       <name>LiquidFlow</name>

       <type>LIQUID_FLOW</type>

       <integration_order>2</integration_order>

       <equation_balance_type>mass</equation_balance_type>

       <process_variables>

         <process_variable>pressure</process_variable>

       </process_variables>

       <specific_body_force>0 0 -9.8</specific_body_force>

       <secondary_variables>

         <secondary_variable internal_name="darcy_velocity" output_name="v" />

       </secondary_variables>

       <aperture_size>

         <parameter>1D_element_cross_section_area</parameter>

       </aperture_size>

     </process>

   </processes>

   <media>

     <medium>

       <phases>

         <phase>

           <type>AqueousLiquid</type>

           <properties>

             <property>

               <name>viscosity</name>

               <type>Constant</type>

               <value>1.e-3</value>

             </property>

             <property>

               <name>density</name>

               <type>Linear</type>

               <reference_value>1000.0</reference_value>

               <independent_variable>

                 <variable_name>liquid_phase_pressure</variable_name>

                 <reference_condition>1e5</reference_condition>

                 <slope>4.6511627906976743356e-10</slope>

               </independent_variable>

             </property>

           </properties>

         </phase>

       </phases>

       <properties>

         <property>

           <name>permeability</name>

           <type>Constant</type>

           <value>1.e-12</value>

         </property>

         <property>

           <name>reference_temperature</name>

           <type>Constant</type>

           <value>293.15</value>

         </property>

         <property>

           <name>porosity</name>

           <type>Constant</type>

           <value>0.2</value>

         </property>

         <property>

           <name>storage</name>

           <type>Constant</type>

           <value>1.e-10</value>

         </property>

       </properties>

     </medium>

   </media>

   <time_loop>

     <processes>

       <process ref="LiquidFlow">

         <nonlinear_solver>basic_picard</nonlinear_solver>

         <convergence_criterion>

           <type>DeltaX</type>

           <norm_type>NORM2</norm_type>

           <abstol>1.e-6</abstol>

         </convergence_criterion>

         <time_discretization>

           <type>BackwardEuler</type>

         </time_discretization>

         <time_stepping>

           <type>FixedTimeStepping</type>

           <t_initial>0.0</t_initial>

           <t_end>8640000</t_end>

           <timesteps>

             <pair>

               <repeat>100</repeat>

               <delta_t>86400</delta_t>

             </pair>

           </timesteps>

         </time_stepping>

       </process>

     </processes>

     <output>

       <type>VTK</type>

       <prefix>line_fractures_in_3D</prefix>

       <timesteps>

         <pair>

           <repeat>10</repeat>

           <each_steps>10</each_steps>

         </pair>

       </timesteps>

       <variables>

         <variable>pressure</variable>

         <variable>v</variable>

       </variables>

       <suffix>ts{:timestep}_t_{:time}</suffix>

     </output>

   </time_loop>

   <parameters>

     <parameter>

       <name>1D_element_cross_section_area</name>

       <type>Constant</type>

       <value>1.e-4</value>

     </parameter>

     <parameter>

       <name>p0</name>

       <type>Constant</type>

       <value>1.0e+5</value>

     </parameter>

     <parameter>

       <name>p_top</name>

       <type>Constant</type>

       <value>5.0e+6</value>

     </parameter>

     <parameter>

       <name>p_bottom</name>

       <type>Constant</type>

       <value>1e+5</value>

     </parameter>

   </parameters>

   <process_variables>

     <process_variable>

       <name>pressure</name>

       <components>1</components>

       <order>1</order>

       <initial_condition>p0</initial_condition>

       <boundary_conditions>

         <boundary_condition>

           <mesh>geometry_top_point</mesh>

           <type>Dirichlet</type>

           <parameter>p_top</parameter>

         </boundary_condition>

         <boundary_condition>

           <mesh>geometry_bottom_point</mesh>

           <type>Dirichlet</type>

           <parameter>p_bottom</parameter>

         </boundary_condition>

       </boundary_conditions>

     </process_variable>

   </process_variables>

   <nonlinear_solvers>

     <nonlinear_solver>

       <name>basic_picard</name>

       <type>Picard</type>

       <max_iter>10</max_iter>

       <linear_solver>general_linear_solver</linear_solver>

     </nonlinear_solver>

   </nonlinear_solvers>

   <linear_solvers>

     <linear_solver>

       <name>general_linear_solver</name>

       <lis>-i cg -p jacobi -tol 1e-20 -maxiter 10000</lis>

       <eigen>

         <solver_type>CG</solver_type>

         <precon_type>DIAGONAL</precon_type>

         <max_iteration_step>10000</max_iteration_step>

         <error_tolerance>1e-20</error_tolerance>

       </eigen>

       <petsc>

         <prefix>lf</prefix>

         <parameters>-lf_ksp_type cg -lf_pc_type bjacobi -lf_ksp_rtol 1e-16 -lf_ksp_max_it 10000</parameters>

       </petsc>

     </linear_solver>

   </linear_solvers>

 </OpenGeoSysProject>