[FEM] Elmer: don't hardcode the coordinate system

- Elmer allows for all currently supported equations several coordinate systems
- also remove an unused variable

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

@@ -35,10 +35,10 @@ import FreeCAD
 
 from . import tasks
 from .equations import elasticity
+from .equations import electricforce
 from .equations import electrostatic
 from .equations import flow
 from .equations import flux
-from .equations import electricforce
 from .equations import heat
 from .. import run
 from .. import solverbase
@@ -47,6 +47,10 @@ from femtools import femutils
 if FreeCAD.GuiUp:
     import FemGui
 
+COORDINATE_SYSTEM = ["Cartesian 1D", "Cartesian 2D", "Cartesian 3D",
+                     "Polar 2D", "Polar 3D",
+                     "Cylindric", "Cylindric Symmetric",
+                     "Axi Symmetric"]
 SIMULATION_TYPE = ["Scanning", "Steady State", "Transient"]
 
 
@@ -72,6 +76,15 @@ class Proxy(solverbase.Proxy):
     def __init__(self, obj):
         super(Proxy, self).__init__(obj)
 
+        obj.addProperty(
+            "App::PropertyEnumeration",
+            "CoordinateSystem",
+            "Coordinate System",
+            ""
+        )
+        obj.CoordinateSystem = COORDINATE_SYSTEM
+        obj.CoordinateSystem = "Cartesian 3D"
+
         obj.addProperty(
             "App::PropertyIntegerConstraint",
             "BDFOrder",

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

@@ -60,7 +60,6 @@ _STARTINFO_NAME = "ELMERSOLVER_STARTINFO"
 _SIF_NAME = "case.sif"
 _ELMERGRID_IFORMAT = "8"
 _ELMERGRID_OFORMAT = "2"
-_SOLID_PREFIX = "Solid"
 
 
 def _getAllSubObjects(obj):
@@ -320,7 +319,7 @@ class Writer(object):
                 hasHeat = True
         if hasHeat:
             self._simulation("BDF Order", self.solver.BDFOrder)
-        self._simulation("Coordinate System", "Cartesian 3D")
+        self._simulation("Coordinate System", self.solver.CoordinateSystem)
         self._simulation("Coordinate Mapping", (1, 2, 3))
         # Elmer uses SI base units, but our mesh is in mm, therefore we must tell
         # the solver that we have another scale
@@ -350,6 +349,15 @@ class Writer(object):
 
     def _updateSimulation(self, solver):
         # updates older simulations
+        if not hasattr(self.solver, "CoordinateSystem"):
+            solver.addProperty(
+                "App::PropertyEnumeration",
+                "CoordinateSystem",
+                "Coordinate System",
+                ""
+            )
+            solver.CoordinateSystem = solverClass.COORDINATE_SYSTEM
+            solver.CoordinateSystem = "Cartesian 3D"
         if not hasattr(self.solver, "BDFOrder"):
             solver.addProperty(
                 "App::PropertyIntegerConstraint",
@@ -409,7 +417,9 @@ class Writer(object):
                 for body in activeIn:
                     if not self._isBodyMaterialFluid(body):
                         self._addSolver(body, solverSection)
-                        self._handleElasticityEquation(activeIn, equation)
+                        # "Plane Stress" is only possible for 2D
+                        if self.solver.CoordinateSystem == "Cartesian 2D":
+                            self._handleElasticityEquation(activeIn, equation)
         if activeIn:
             self._handleElasticityConstants()
             self._handleElasticityBndConditions()