Merge pull request festim-dev#774 from festim-dev/IC-heat-transfer

IC improvements for Heat Transfer

docs/source/userguide/temperature.rst

@@ -68,6 +68,17 @@ For a steady-state problem:
 
 :ref:`Boundary conditions<boundary conditions>` and :ref:`heat sources<sources>` can then be applied to this heat transfer problem.
 
+For transient problems, an initial condition is required:
+
+.. code-block:: python
+
+    model.T = HeatTransferProblem(
+        transient=True,
+        initial_condition=300,
+    )
+
+Initial conditions can be given as float, sympy expressions or a :class:`festim.InitialCondition` instance in order to read from a XDMF file (see :ref:`Initial Conditions<Initial Conditions>` for more details).
+
 ----------------
 From a XDMF file
 ----------------

festim/temperature/temperature_solver.py

@@ -8,7 +8,7 @@ class HeatTransferProblem(festim.Temperature):
     Args:
         transient (bool, optional): If True, a transient simulation will
             be run. Defaults to True.
-        initial_condition (festim.InitialCondition, optional): The initial condition.
+        initial_condition (int, float, sp.Expr, festim.InitialCondition, optional): The initial condition.
             Only needed if transient is True.
         absolute_tolerance (float, optional): the absolute tolerance of the newton
             solver. Defaults to 1e-03
@@ -56,6 +56,17 @@ def __init__(
         self.boundary_conditions = []
         self.sub_expressions = []
 
+    @property
+    def initial_condition(self):
+        return self._initial_condition
+
+    @initial_condition.setter
+    def initial_condition(self, value):
+        if isinstance(value, (int, float, sp.Expr)):
+            self._initial_condition = festim.InitialCondition(field="T", value=value)
+        else:
+            self._initial_condition = value
+
     # TODO rename initialise?
     def create_functions(self, materials, mesh, dt=None):
         """Creates functions self.T, self.T_n and test function self.v_T.
@@ -73,7 +84,10 @@ def create_functions(self, materials, mesh, dt=None):
         self.T = f.Function(V, name="T")
         self.T_n = f.Function(V, name="T_n")
         self.v_T = f.TestFunction(V)
-
+        if self.transient and self.initial_condition is None:
+            raise AttributeError(
+                "Initial condition is required for transient heat transfer simulations"
+            )
         if self.transient and self.initial_condition:
             if isinstance(self.initial_condition.value, str):
                 if self.initial_condition.value.endswith(".xdmf"):

test/system/test_misc.py

@@ -331,3 +331,23 @@ def test_materials_setter():
     test_materials = F.Materials([])
     my_model.materials = test_materials
     assert my_model.materials is test_materials
+
+
+def test_error_raised_when_no_IC_heat_transfer():
+    """
+    Checks that an error is raised when no initial condition is provided for
+    transient heat transfer simulations
+    """
+    my_model = F.Simulation()
+
+    my_model.T = F.HeatTransferProblem(transient=True, initial_condition=None)
+    my_model.mesh = F.MeshFromVertices(np.linspace(0, 1, 10))
+    my_model.materials = F.Material(1, 1, 0.1)
+    my_model.settings = F.Settings(1e-10, 1e-10, final_time=1e-7)
+    my_model.dt = F.Stepsize(1e-9)
+
+    with pytest.raises(
+        AttributeError,
+        match="Initial condition is required for transient heat transfer simulations",
+    ):
+        my_model.initialise()

test/unit/test_temperature.py

@@ -69,9 +69,7 @@ def thermal_cond(a):
     bc1 = festim.DirichletBC(surfaces=[1], value=u, field="T")
     bc2 = festim.FluxBC(surfaces=[2], value=2, field="T")
 
-    my_temp = festim.HeatTransferProblem(
-        transient=True, initial_condition=festim.InitialCondition(field="T", value=0)
-    )
+    my_temp = festim.HeatTransferProblem(transient=True, initial_condition=0)
     my_temp.boundary_conditions = [bc1, bc2]
     my_temp.sources = [festim.Source(-4, volume=[1], field="T")]
     my_temp.create_functions(my_mats, my_mesh, dt=dt)
@@ -133,6 +131,30 @@ class is created from this file and the error norm between the written and
     assert error_L2 < 1e-9
 
 
+def test_temperature_with_expr():
+    """
+    Test for the InitialCondition.create_functions() with a sympy expression
+    and checks that the error norm between the expected and computed
+    functions is below a certain threshold.
+    """
+    # create function to be comapared
+    mesh = fenics.UnitSquareMesh(10, 10)
+    # TempFromXDMF needs a festim mesh
+    my_mesh = festim.Mesh()
+    my_mesh.dx = fenics.dx
+    my_mesh.ds = fenics.ds
+    my_mesh.mesh = mesh
+    my_mats = festim.Materials(
+        [festim.Material(id=1, D_0=1, E_D=0, thermal_cond=1, heat_capacity=1, rho=1)]
+    )
+    my_T = festim.HeatTransferProblem(transient=True, initial_condition=300 + festim.x)
+    my_T.create_functions(mesh=my_mesh, materials=my_mats, dt=festim.Stepsize(2))
+
+    expected_expr = fenics.Expression("300 + x[0]", degree=2)
+    error_L2 = fenics.errornorm(expected_expr, my_T.T_n, "L2")
+    assert error_L2 < 1e-9
+
+
 def test_temperature_from_xdmf_create_functions(tmpdir):
     """Test for the TemperatureFromXDMF.create_functions().
     Creates a function, writes it to an XDMF file, then a TemperatureFromXDMF