Fem: Add support for Elmer static current solver - fixes #11895

src/Mod/Fem/CMakeLists.txt

@@ -285,6 +285,8 @@ SET(FemSolverElmerEquations_SRCS
     femsolver/elmer/equations/magnetodynamic2D.py
     femsolver/elmer/equations/magnetodynamic2D_writer.py
     femsolver/elmer/equations/nonlinear.py
+    femsolver/elmer/equations/staticcurrent.py
+    femsolver/elmer/equations/staticcurrent_writer.py
 )
 
 SET(FemSolverFenics_SRCS

src/Mod/Fem/Gui/Command.cpp

@@ -1542,6 +1542,9 @@ void CmdFemCompEmEquations::activated(int iMsg)
     else if (iMsg == 3) {
         rcCmdMgr.runCommandByName("FEM_EquationMagnetodynamic2D");
     }
+    else if (iMsg == 4) {
+        rcCmdMgr.runCommandByName("FEM_EquationStaticCurrent");
+    }
     else {
         return;
     }
@@ -1569,6 +1572,8 @@ Gui::Action* CmdFemCompEmEquations::createAction()
     cmd2->setIcon(Gui::BitmapFactory().iconFromTheme("FEM_EquationMagnetodynamic"));
     QAction* cmd3 = pcAction->addAction(QString());
     cmd3->setIcon(Gui::BitmapFactory().iconFromTheme("FEM_EquationMagnetodynamic2D"));
+    QAction* cmd4 = pcAction->addAction(QString());
+    cmd4->setIcon(Gui::BitmapFactory().iconFromTheme("FEM_EquationStaticCurrent"));
 
     _pcAction = pcAction;
     languageChange();
@@ -1637,6 +1642,17 @@ void CmdFemCompEmEquations::languageChange()
         cmd3->setStatusTip(QApplication::translate("FEM_EquationMagnetodynamic2D",
                                                    EquationMagnetodynamic2D->getStatusTip()));
     }
+
+    Gui::Command* EquationStaticCurrent = rcCmdMgr.getCommandByName("FEM_EquationStaticCurrent");
+    if (EquationStaticCurrent) {
+        QAction* cmd4 = a[4];
+        cmd4->setText(QApplication::translate("FEM_EquationStaticCurrent",
+                                              EquationStaticCurrent->getMenuText()));
+        cmd4->setToolTip(QApplication::translate("FEM_EquationStaticCurrent",
+                                                 EquationStaticCurrent->getToolTipText()));
+        cmd4->setStatusTip(QApplication::translate("FEM_EquationStaticCurrent",
+                                                   EquationStaticCurrent->getStatusTip()));
+    }
 }
 
 bool CmdFemCompEmEquations::isActive()

src/Mod/Fem/Gui/Resources/Fem.qrc

@@ -51,6 +51,7 @@
         <file>icons/FEM_EquationHeat.svg</file>
         <file>icons/FEM_EquationMagnetodynamic.svg</file>
         <file>icons/FEM_EquationMagnetodynamic2D.svg</file>
+        <file>icons/FEM_EquationStaticCurrent.svg</file>
 
         <!-- gui command icons: meshes -->
         <file>icons/FEM_CreateElementsSet.svg</file>

src/Mod/Fem/Gui/Resources/ui/CurrentDensity.ui

@@ -345,6 +345,41 @@ Note: for 2D only setting for x is possible,
      </property>
     </widget>
    </item>
+   <item row="5" column="0">
+    <widget class="QLabel" name="l_normal">
+     <property name="text">
+      <string>Normal:</string>
+     </property>
+    </widget>
+   </item>
+   <item row="5" column="1">
+    <widget class="Gui::QuantitySpinBox" name="normalQSB">
+     <property name="enabled">
+      <bool>true</bool>
+     </property>
+     <property name="unit" stdset="0">
+      <string notr="true">A/m^2</string>
+     </property>
+     <property name="alignment">
+      <set>Qt::AlignLeft|Qt::AlignTrailing|Qt::AlignVCenter</set>
+     </property>
+     <property name="keyboardTracking">
+      <bool>true</bool>
+     </property>
+     <property name="minimum">
+      <double>-1000000000000000000000.000000000000000</double>
+     </property>
+     <property name="maximum">
+      <double>1000000000000000000000.000000000000000</double>
+     </property>
+     <property name="singleStep">
+      <double>1.000000000000000</double>
+     </property>
+     <property name="value">
+      <double>0.000000000000</double>
+     </property>
+    </widget>
+   </item>
   </layout>
  </widget>
  <customwidgets>

src/Mod/Fem/ObjectsFem.py

@@ -767,6 +767,17 @@ def makeEquationMagnetodynamic2D(doc, base_solver=None, name="Magnetodynamic2D")
     return obj
 
 
+def makeEquationStaticCurrent(doc, base_solver=None, name="StaticCurrent"):
+    """makeEquationStaticCurrent(document, [base_solver], [name]):
+    creates a FEM static current equation for a solver"""
+    from femsolver.elmer.equations import staticcurrent
+
+    obj = staticcurrent.create(doc, name)
+    if base_solver:
+        base_solver.addObject(obj)
+    return obj
+
+
 def makeSolverCalculiXCcxTools(doc, name="SolverCcxTools"):
     """makeSolverCalculiXCcxTools(document, [name]):
     makes a Calculix solver object for the ccx tools module"""

src/Mod/Fem/femcommands/commands.py

@@ -502,6 +502,19 @@ class _EquationMagnetodynamic2D(CommandManager):
         self.do_activated = "add_obj_on_gui_selobj_expand_noset_edit"
 
 
+class _EquationStaticCurrent(CommandManager):
+    "The FEM_EquationStaticCurrent command definition"
+
+    def __init__(self):
+        super().__init__()
+        self.menutext = Qt.QT_TRANSLATE_NOOP("FEM_EquationStaticCurrent", "Static current equation")
+        self.tooltip = Qt.QT_TRANSLATE_NOOP(
+            "FEM_EquationStaticCurrent", "Creates a FEM equation for static current"
+        )
+        self.is_active = "with_solver_elmer"
+        self.do_activated = "add_obj_on_gui_selobj_expand_noset_edit"
+
+
 class _Examples(CommandManager):
     "The FEM_Examples command definition"
 
@@ -1179,6 +1192,7 @@ FreeCADGui.addCommand("FEM_EquationFlux", _EquationFlux())
 FreeCADGui.addCommand("FEM_EquationHeat", _EquationHeat())
 FreeCADGui.addCommand("FEM_EquationMagnetodynamic", _EquationMagnetodynamic())
 FreeCADGui.addCommand("FEM_EquationMagnetodynamic2D", _EquationMagnetodynamic2D())
+FreeCADGui.addCommand("FEM_EquationStaticCurrent", _EquationStaticCurrent())
 FreeCADGui.addCommand("FEM_Examples", _Examples())
 FreeCADGui.addCommand("FEM_MaterialEditor", _MaterialEditor())
 FreeCADGui.addCommand("FEM_MaterialFluid", _MaterialFluid())

src/Mod/Fem/femobjects/constraint_currentdensity.py

@@ -98,6 +98,15 @@ class ConstraintCurrentDensity(base_fempythonobject.BaseFemPythonObject):
             )
             obj.setPropertyStatus("CurrentDensity_im_3", "LockDynamic")
             obj.CurrentDensity_im_3 = "0 A/m^2"
+        if not hasattr(obj, "NormalCurrentDensity"):
+            obj.addProperty(
+                "App::PropertyCurrentDensity",
+                "NormalCurrentDensity",
+                "Current Density",
+                "Current density normal to boundary",
+            )
+            obj.setPropertyStatus("NormalCurrentDensity", "LockDynamic")
+            obj.NormalCurrentDensity = "0 A/m^2"
 
         # now the enable bools
         if not hasattr(obj, "CurrentDensity_re_1_Disabled"):

src/Mod/Fem/femsolver/elmer/equations/staticcurrent.py

@@ -0,0 +1,90 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+# ***************************************************************************
+# *   Copyright (c) 2025 Mario Passaglia <mpassaglia[at]cbc.uba.ar>         *
+# *                                                                         *
+# *   This file is part of FreeCAD.                                         *
+# *                                                                         *
+# *   FreeCAD is free software: you can redistribute it and/or modify it    *
+# *   under the terms of the GNU Lesser General Public License as           *
+# *   published by the Free Software Foundation, either version 2.1 of the  *
+# *   License, or (at your option) any later version.                       *
+# *                                                                         *
+# *   FreeCAD 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      *
+# *   Lesser General Public License for more details.                       *
+# *                                                                         *
+# *   You should have received a copy of the GNU Lesser General Public      *
+# *   License along with FreeCAD. If not, see                               *
+# *   <https://www.gnu.org/licenses/>.                                      *
+# *                                                                         *
+# ***************************************************************************
+
+__title__ = "FreeCAD FEM solver Elmer equation object StaticCurrent"
+__author__ = "Mario Passaglia"
+__url__ = "https://www.freecad.org"
+
+## \addtogroup FEM
+#  @{
+
+from femtools import femutils
+from ... import equationbase
+from . import linear
+
+
+def create(doc, name="StaticCurrent"):
+    return femutils.createObject(doc, name, Proxy, ViewProxy)
+
+
+class Proxy(linear.Proxy, equationbase.StaticCurrentProxy):
+
+    Type = "Fem::EquationElmerStaticCurrent"
+
+    def __init__(self, obj):
+        super().__init__(obj)
+
+        obj.addProperty("App::PropertyBool", "CalculateVolumeCurrent", "StaticCurrent", "")
+        obj.CalculateVolumeCurrent = True
+        obj.addProperty("App::PropertyBool", "CalculateJouleHeating", "StaticCurrent", "")
+        obj.addProperty(
+            "App::PropertyBool",
+            "ConstantWeights",
+            "StaticCurrent",
+            "Used to turn constant weighting on for the results",
+        )
+        obj.addProperty(
+            "App::PropertyBool",
+            "CalculateNodalHeating",
+            "StaticCurrent",
+            "Calculate nodal heating that may be used to couple the heat equation optimally when using conforming finite element meshes",
+        )
+        obj.addProperty(
+            "App::PropertyBool",
+            "HeatSource",
+            "StaticCurrent",
+            "Use Joule heating as a heat source in combination with heat equation",
+        )
+        obj.addProperty(
+            "App::PropertyBool",
+            "PowerControl",
+            "StaticCurrent",
+            "Apply power control with the desired heating power",
+        )
+        obj.addProperty(
+            "App::PropertyBool",
+            "CurrentControl",
+            "StaticCurrent",
+            "Apply current control with the desired current",
+        )
+        obj.addProperty(
+            "App::PropertyElectricCurrent", "Current", "StaticCurrent", "Current control value"
+        )
+        obj.addProperty("App::PropertyPower", "Power", "StaticCurrent", "Power control value")
+
+
+class ViewProxy(linear.ViewProxy, equationbase.StaticCurrentViewProxy):
+    pass
+
+
+##  @}

src/Mod/Fem/femsolver/elmer/equations/staticcurrent_writer.py

@@ -0,0 +1,111 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+# ***************************************************************************
+# *   Copyright (c) 2025 Mario Passaglia <mpassaglia[at]cbc.uba.ar>         *
+# *                                                                         *
+# *   This file is part of FreeCAD.                                         *
+# *                                                                         *
+# *   FreeCAD is free software: you can redistribute it and/or modify it    *
+# *   under the terms of the GNU Lesser General Public License as           *
+# *   published by the Free Software Foundation, either version 2.1 of the  *
+# *   License, or (at your option) any later version.                       *
+# *                                                                         *
+# *   FreeCAD 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      *
+# *   Lesser General Public License for more details.                       *
+# *                                                                         *
+# *   You should have received a copy of the GNU Lesser General Public      *
+# *   License along with FreeCAD. If not, see                               *
+# *   <https://www.gnu.org/licenses/>.                                      *
+# *                                                                         *
+# ***************************************************************************
+
+__title__ = "FreeCAD FEM StaticCurrent Elmer writer"
+__author__ = "Mario Passaglia"
+__url__ = "https://www.freecad.org"
+
+## \addtogroup FEM
+#  @{
+
+from FreeCAD import Units
+from .. import sifio
+
+
+class SCwriter:
+
+    def __init__(self, writer, solver):
+        self.write = writer
+        self.solver = solver
+
+    def getStaticCurrentSolver(self, equation):
+        # output the equation parameters
+        s = self.write.createLinearSolver(equation)
+        s["Equation"] = "Stat Current Solver"
+        s["Procedure"] = sifio.FileAttr("StatCurrentSolve/StatCurrentSolver")
+        s["Variable"] = self.write.getUniqueVarName("Potential")
+        s["Variable DOFs"] = 1
+        s["Calculate Volume Current"] = equation.CalculateVolumeCurrent
+        s["Calculate Joule Heating"] = equation.CalculateJouleHeating
+        s["Constant Weights"] = equation.ConstantWeights
+        s["Calculate Nodal Heating"] = equation.CalculateNodalHeating
+        if equation.PowerControl:
+            s["Power Control"] = equation.Power.getValueAs("W").Value
+        if equation.CurrentControl:
+            s["Current Control"] = equation.Current.getValueAs("A").Value
+        s["Exec Solver"] = "Always"
+        s["Optimize Bandwidth"] = True
+        s["Stabilize"] = equation.Stabilize
+
+        return s
+
+    def handleStaticCurrentConstants(self):
+        pass
+
+    def handleStaticCurrentMaterial(self, bodies):
+        for obj in self.write.getMember("App::MaterialObject"):
+            m = obj.Material
+            refs = obj.References[0][1] if obj.References else self.write.getAllBodies()
+            for name in (n for n in refs if n in bodies):
+                self.write.material(name, "Name", m["Name"])
+                if "ElectricalConductivity" in m:
+                    self.write.material(
+                        name,
+                        "Electric Conductivity",
+                        Units.Quantity(m["ElectricalConductivity"]).getValueAs("S/m").Value,
+                    )
+
+    def handleStaticCurrentBndConditions(self):
+        for obj in self.write.getMember("Fem::ConstraintElectrostaticPotential"):
+            if obj.References:
+                for name in obj.References[0][1]:
+                    # output the FreeCAD label as comment
+                    if obj.Label:
+                        self.write.boundary(name, "! FreeCAD Name", obj.Label)
+                    if obj.BoundaryCondition == "Dirichlet":
+                        if obj.PotentialEnabled:
+                            self.write.boundary(name, "Current Density BC", False)
+                            self.write.boundary(
+                                name, "Potential", obj.Potential.getValueAs("V").Value
+                            )
+                self.write.handled(obj)
+
+        for obj in self.write.getMember("Fem::ConstraintCurrentDensity"):
+            if obj.References:
+                for name in obj.References[0][1]:
+                    # output the FreeCAD label as comment
+                    if obj.Label:
+                        self.write.boundary(name, "! FreeCAD Name", obj.Label)
+                    self.write.boundary(name, "Current Density BC", True)
+                    self.write.boundary(
+                        name, "Current Density", obj.NormalCurrentDensity.getValueAs("A/m^2").Value
+                    )
+
+                self.write.handled(obj)
+
+    def handleStaticCurrentBodyForces(self, bodies, equation):
+        for name in bodies:
+            self.write.bodyForce(name, "Joule Heat", equation.HeatSource)
+
+
+##  @}

src/Mod/Fem/femsolver/elmer/writer.py

@@ -57,6 +57,7 @@ from .equations import flux_writer
 from .equations import heat_writer
 from .equations import magnetodynamic_writer as MgDyn_writer
 from .equations import magnetodynamic2D_writer as MgDyn2D_writer
+from .equations import staticcurrent_writer as SC_writer
 
 
 _STARTINFO_NAME = "ELMERSOLVER_STARTINFO"
@@ -109,6 +110,7 @@ class Writer:
         self._handleFlux()
         self._handleMagnetodynamic()
         self._handleMagnetodynamic2D()
+        self._handleStaticCurrent()
         self._addOutputSolver()
 
         self._writeSif()
@@ -614,6 +616,28 @@ class Writer:
             MgDyn2D.handleMagnetodynamic2DBodyForces(activeIn, equation)
             MgDyn2D.handleMagnetodynamic2DMaterial(activeIn)
 
+    # -------------------------------------------------------------------------------------------
+    # StaticCurrent
+
+    def _handleStaticCurrent(self):
+        SCW = SC_writer.SCwriter(self, self.solver)
+        activeIn = []
+        for equation in self.solver.Group:
+            if femutils.is_of_type(equation, "Fem::EquationElmerStaticCurrent"):
+                if equation.References:
+                    activeIn = equation.References[0][1]
+                else:
+                    activeIn = self.getAllBodies()
+                solverSection = SCW.getStaticCurrentSolver(equation)
+                for body in activeIn:
+                    self._addSolver(body, solverSection)
+                SCW.handleStaticCurrentBodyForces(activeIn, equation)
+
+        if activeIn:
+            SCW.handleStaticCurrentConstants()
+            SCW.handleStaticCurrentBndConditions()
+            SCW.handleStaticCurrentMaterial(activeIn)
+
     # -------------------------------------------------------------------------------------------
     # Solver handling
 

src/Mod/Fem/femsolver/equationbase.py

@@ -157,4 +157,14 @@ class Magnetodynamic2DViewProxy(BaseViewProxy):
         return ":/icons/FEM_EquationMagnetodynamic2D.svg"
 
 
+class StaticCurrentProxy(BaseProxy):
+    pass
+
+
+class StaticCurrentViewProxy(BaseViewProxy):
+
+    def getIcon(self):
+        return ":/icons/FEM_EquationStaticCurrent.svg"
+
+
 ##  @}

src/Mod/Fem/femtaskpanels/task_constraint_currentdensity.py

@@ -123,6 +123,10 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
         FreeCADGui.ExpressionBinding(self._paramWidget.imagZQSB).bind(
             self.obj, "CurrentDensity_im_3"
         )
+        self._paramWidget.normalQSB.setProperty("value", self.obj.NormalCurrentDensity)
+        FreeCADGui.ExpressionBinding(self._paramWidget.normalQSB).bind(
+            self.obj, "NormalCurrentDensity"
+        )
 
         self._paramWidget.reXunspecBox.setChecked(self.obj.CurrentDensity_re_1_Disabled)
         self._paramWidget.reYunspecBox.setChecked(self.obj.CurrentDensity_re_2_Disabled)
@@ -176,3 +180,4 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
                 self._paramWidget.imZunspecBox, self._paramWidget.imagZQSB
             )
         )
+        self.obj.NormalCurrentDensity = self._paramWidget.normalQSB.property("value")