[FEM] add example for flux equation

- also fine-tune flow example

src/Mod/Fem/CMakeLists.txt

@@ -78,6 +78,7 @@ SET(FemExamples_SRCS
     femexamples/equation_electrostatics_capacitance_two_balls.py
     femexamples/equation_electrostatics_electricforce_elmer_nongui6.py
     femexamples/equation_flow_elmer_2D.py
+    femexamples/equation_flux_elmer.py
     femexamples/frequency_beamsimple.py
     femexamples/manager.py
     femexamples/material_multiple_bendingbeam_fiveboxes.py

src/Mod/Fem/femexamples/equation_flow_elmer_2D.py

@@ -40,8 +40,8 @@ def get_information():
         "name": "Flow - Elmer 2D",
         "meshtype": "solid",
         "meshelement": "Tet10",
-        "constraints": ["initial pressure", "initial velocity",
-                        "velocity", "initial temperature", "temperature"],
+        "constraints": ["initial pressure", "initial temperature", "initial velocity",
+                        "temperature", "velocity"],
         "solvers": ["elmer"],
         "material": "fluid",
         "equations": ["flow", "heat"]
@@ -119,8 +119,8 @@ def setup(doc=None, solvertype="elmer"):
     # solver
     if solvertype == "elmer":
         solver_obj = ObjectsFem.makeSolverElmer(doc, "SolverElmer")
-        solver_flow = ObjectsFem.makeEquationFlow(doc, solver_obj)
-        solver_heat = ObjectsFem.makeEquationHeat(doc, solver_obj)
+        equation_flow = ObjectsFem.makeEquationFlow(doc, solver_obj)
+        equation_heat = ObjectsFem.makeEquationHeat(doc, solver_obj)
     else:
         FreeCAD.Console.PrintWarning(
             "Not known or not supported solver type: {}. "
@@ -130,15 +130,13 @@ def setup(doc=None, solvertype="elmer"):
     analysis.addObject(solver_obj)
 
     # solver settings
-    solver_flow.Priority = 10
-    solver_flow.IdrsParameter = 3
-    solver_flow.LinearIterativeMethod = "Idrs"
-    solver_flow.LinearPreconditioning = "ILU1"
-    solver_heat.Priority = 20
-    solver_heat.IdrsParameter = 3
-    solver_heat.LinearIterativeMethod = "Idrs"
-    solver_heat.LinearPreconditioning = "ILU1"
-    solver_heat.RelaxationFactor = 0.9
+    equation_flow.IdrsParameter = 3
+    equation_flow.LinearIterativeMethod = "Idrs"
+    equation_flow.LinearPreconditioning = "ILU1"
+    equation_heat.IdrsParameter = 3
+    equation_heat.LinearIterativeMethod = "Idrs"
+    equation_heat.LinearPreconditioning = "ILU1"
+    equation_heat.RelaxationFactor = 0.9
 
     # material
     material_obj = ObjectsFem.makeMaterialFluid(doc, "Material_Fluid")

src/Mod/Fem/femexamples/equation_flux_elmer.py

@@ -0,0 +1,166 @@
+# ***************************************************************************
+# *   Copyright (c) 2023 Uwe Stöhr <uwestoehr@lyx.org>                      *
+# *                                                                         *
+# *   This file is part of the FreeCAD CAx development system.              *
+# *                                                                         *
+# *   This program is free software; you can redistribute it and/or modify  *
+# *   it under the terms of the GNU Lesser General Public License (LGPL)    *
+# *   as published by the Free Software Foundation; either version 2 of     *
+# *   the License, or (at your option) any later version.                   *
+# *   for detail see the LICENCE text file.                                 *
+# *                                                                         *
+# *   This program 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 Library General Public License for more details.                  *
+# *                                                                         *
+# *   You should have received a copy of the GNU Library General Public     *
+# *   License along with this program; if not, write to the Free Software   *
+# *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  *
+# *   USA                                                                   *
+# *                                                                         *
+# ***************************************************************************
+
+import sys
+import FreeCAD
+from FreeCAD import Vector
+
+import ObjectsFem
+
+from . import manager
+from .manager import get_meshname
+from .manager import init_doc
+
+def get_information():
+    return {
+        "name": "Flux - Elmer",
+        "meshtype": "solid",
+        "meshelement": "Tet10",
+        "constraints": ["electrostatic potential", "temperature"],
+        "solvers": ["elmer"],
+        "material": "solid",
+        "equations": ["electrostatic", "flux", "heat"]
+    }
+
+def get_explanation(header=""):
+    return header + """
+
+To run the example from Python console use:
+from femexamples.equation_flux_elmer import setup
+setup()
+
+Flow and Heat equation in FreeCAD FEM-Elmer
+
+"""
+
+def setup(doc=None, solvertype="elmer"):
+
+    # init FreeCAD document
+    if doc is None:
+        doc = init_doc()
+
+    # explanation object
+    # just keep the following line and change text string in get_explanation method
+    manager.add_explanation_obj(doc, get_explanation(manager.get_header(get_information())))
+
+    # geometric object
+    cube = doc.addObject("Part::Box", "Cube")
+
+    # set view
+    doc.recompute()
+    if FreeCAD.GuiUp:
+        cube.ViewObject.Transparency = 50
+        cube.ViewObject.Document.activeView().viewAxonometric()
+        cube.ViewObject.Document.activeView().fitAll()
+
+    # analysis
+    analysis = ObjectsFem.makeAnalysis(doc, "Analysis")
+    if FreeCAD.GuiUp:
+        import FemGui
+        FemGui.setActiveAnalysis(analysis)
+
+    # solver
+    if solvertype == "elmer":
+        solver_obj = ObjectsFem.makeSolverElmer(doc, "SolverElmer")
+        equation_electrostatic = ObjectsFem.makeEquationElectrostatic(doc, solver_obj)
+        equation_heat = ObjectsFem.makeEquationHeat(doc, solver_obj)
+        equation_flux_potential = ObjectsFem.makeEquationFlux(doc, solver_obj)
+        equation_flux_temperature = ObjectsFem.makeEquationFlux(doc, solver_obj)
+    else:
+        FreeCAD.Console.PrintWarning(
+            "Not known or not supported solver type: {}. "
+            "No solver object was created.\n".format(solvertype)
+        )
+        return doc
+    analysis.addObject(solver_obj)
+
+    # solver settings
+    equation_flux_potential.Label = "Flux_Potential"
+    equation_flux_potential.FluxCoefficient = "None"
+    equation_flux_potential.FluxVariable = "Potential"
+    equation_flux_temperature.Label = "Flux_Temperature"
+
+    # material
+    material_obj = ObjectsFem.makeMaterialSolid(doc, "Graphite")
+    mat = material_obj.Material
+    mat["Name"] = "Graphite"
+    mat["Density"] = "1750.0 kg/m^3"
+    mat["PoissonRatio"] = "0.20"
+    mat["ThermalConductivity"] = "96 W/m/K"
+    mat["ThermalExpansionCoefficient"] = "8 µm/m/K"
+    mat["SpecificHeat"] = "720.00 J/kg/K"
+    mat["RelativePermittivity"] = "0.7"
+    mat["ElectricalConductivity"] = "2e4 S/m"
+    mat["RelativePermeability"] = "1.0"
+    material_obj.Material = mat
+    material_obj.References = [(cube, "Solid1")]
+    analysis.addObject(material_obj)
+
+    # constraint potential 1V
+    Potential_1V = ObjectsFem.makeConstraintElectrostaticPotential(doc, "Potential_1V")
+    Potential_1V.Potential = "1 V"
+    Potential_1V.NormalDirection = Vector(0, -1, 0)
+    Potential_1V.References = [(cube, "Face3")]
+    analysis.addObject(Potential_1V)
+
+    # constraint potential 0V
+    Potential_0V = ObjectsFem.makeConstraintElectrostaticPotential(doc, "Potential_0V")
+    Potential_0V.Potential = "0 V"
+    Potential_0V.NormalDirection = Vector(0, 0, 0)
+    Potential_0V.References = [(cube, "Face4")]
+    analysis.addObject(Potential_0V)
+
+    # constraint wall temperature
+    Temperature_300K = ObjectsFem.makeConstraintTemperature(doc, "Temperature_300K")
+    Temperature_300K.Temperature = 300.0
+    Temperature_300K.NormalDirection = Vector(-1, 0, 0)
+    Temperature_300K.References = [(cube, "Face1")]
+    analysis.addObject(Temperature_300K)
+
+    # constraint inlet temperature
+    Temperature_600K = ObjectsFem.makeConstraintTemperature(doc, "Temperature_600K")
+    Temperature_600K.Temperature = 600.0
+    Temperature_600K.NormalDirection = Vector(1, 0, 0)
+    Temperature_600K.References = [(cube, "Face2")]
+    analysis.addObject(Temperature_600K)
+
+    # mesh
+    femmesh_obj = analysis.addObject(ObjectsFem.makeMeshGmsh(doc, get_meshname()))[0]
+    femmesh_obj.Part = cube
+    femmesh_obj.CharacteristicLengthMax = "1 mm"
+    femmesh_obj.ViewObject.Visibility = False
+
+    # generate the mesh
+    from femmesh import gmshtools
+    gmsh_mesh = gmshtools.GmshTools(femmesh_obj, analysis)
+    try:
+        error = gmsh_mesh.create_mesh()
+    except Exception:
+        error = sys.exc_info()[1]
+        FreeCAD.Console.PrintError(
+            "Unexpected error when creating mesh: {}\n"
+            .format(error)
+        )
+
+    doc.recompute()
+    return doc

src/Mod/Fem/femexamples/manager.py

@@ -71,6 +71,7 @@ def run_all():
     run_example("equation_electrostatics_capacitance_two_balls", run_solver=True)
     run_example("equation_electrostatics_electricforce_elmer_nongui6", run_solver=True)
     run_example("equation_flow_elmer_2D", run_solver=True)
+    run_example("equation_flux_elmer", run_solver=True)
     run_example("frequency_beamsimple", run_solver=True)
     run_example("material_multiple_bendingbeam_fiveboxes", run_solver=True)
     run_example("material_multiple_bendingbeam_fivefaces", run_solver=True)
@@ -104,6 +105,7 @@ def setup_all():
     run_example("equation_electrostatics_capacitance_two_balls")
     run_example("equation_electrostatics_electricforce_elmer_nongui6")
     run_example("equation_flow_elmer_2D")
+    run_example("equation_flux_elmer")
     run_example("frequency_beamsimple")
     run_example("material_multiple_bendingbeam_fiveboxes")
     run_example("material_multiple_bendingbeam_fivefaces")