 <OpenGeoSysProject>

   <meshes>

     <mesh>cube_1x1x1_hex_1e3.vtu</mesh>

     <mesh>cube_1x1x1_hex_1e3_back.vtu</mesh>

     <mesh>cube_1x1x1_hex_1e3_bottom.vtu</mesh>

     <mesh>cube_1x1x1_hex_1e3_front.vtu</mesh>

     <mesh>cube_1x1x1_hex_1e3_left.vtu</mesh>

     <mesh>cube_1x1x1_hex_1e3_right.vtu</mesh>

     <mesh>cube_1x1x1_hex_1e3_top.vtu</mesh>

   </meshes>

   <processes>

     <process>

       <name>GW23</name>

       <type>STEADY_STATE_DIFFUSION</type>

       <integration_order>2</integration_order>

       <process_variables>

         <process_variable>pressure</process_variable>

       </process_variables>

       <secondary_variables>

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

       </secondary_variables>

     </process>

   </processes>

   <time_loop>

     <processes>

       <process ref="GW23">

         <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>SingleStep</type>

         </time_stepping>

       </process>

     </processes>

     <output>

       <type>VTK</type>

       <prefix>cube_1e3_neumann</prefix>

       <variables>

         <variable>pressure</variable>

         <variable>v</variable>

       </variables>

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

     </output>

   </time_loop>

   <media>

     <medium id="0">

       <phases />

       <properties>

         <property>

           <name>diffusion</name>

           <type>Constant</type>

           <value>1</value>

         </property>

         <property>

           <name>reference_temperature</name>

           <type>Constant</type>

           <value>293.15</value>

         </property>

       </properties>

     </medium>

   </media>

   <parameters>

     <parameter>

       <name>p0</name>

       <type>Constant</type>

       <value>0</value>

     </parameter>

     <parameter>

       <name>p_neumann</name>

       <type>Constant</type>

       <value>1</value>

     </parameter>

     <parameter>

       <name>p_Dirichlet</name>

       <type>Constant</type>

       <value>1</value>

     </parameter>

   </parameters>

   <process_variables>

     <process_variable>

       <name>pressure</name>

       <mesh>cube_1x1x1_hex_1e3</mesh>

       <components>1</components>

       <order>1</order>

       <initial_condition>p0</initial_condition>

       <boundary_conditions>

         <boundary_condition>

           <mesh>cube_1x1x1_hex_1e3_left</mesh>

           <type>Dirichlet</type>

           <parameter>p_Dirichlet</parameter>

         </boundary_condition>

         <boundary_condition>

           <mesh>cube_1x1x1_hex_1e3_front</mesh>

           <type>Dirichlet</type>

           <parameter>p_Dirichlet</parameter>

         </boundary_condition>

         <boundary_condition>

           <mesh>cube_1x1x1_hex_1e3_right</mesh>

           <type>Neumann</type>

           <parameter>p_neumann</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-16 -maxiter 10000</lis>

       <eigen>

         <solver_type>CG</solver_type>

         <precon_type>DIAGONAL</precon_type>

         <max_iteration_step>10000</max_iteration_step>

         <error_tolerance>1e-16</error_tolerance>

       </eigen>

       <petsc>

         <prefix>gw</prefix>

         <parameters>-gw_ksp_type cg -gw_pc_type jacobi -gw_ksp_rtol 1.e-16 -gw_ksp_max_it 10000</parameters>

       </petsc>

     </linear_solver>

   </linear_solvers>

 </OpenGeoSysProject>