Add unstructured 2D/3D DFN battery models

CHANGELOG.md

@@ -8,6 +8,7 @@
 
 ## Features
 
+- Added basic unstructured 2D/3D DFN models (`BasicDFN2DUnstructured`, `BasicDFN3DUnstructured`). ([#5690](https://github.com/pybamm-team/PyBaMM/pull/5690))
 - Added VTK-based plotting (`VTKQuickPlot`) for unstructured mesh solutions, including headless CI OpenGL setup. ([#5689](https://github.com/pybamm-team/PyBaMM/pull/5689))
 - Added `FiniteVolumeUnstructured` spatial method and unstructured processed-variable support for cell-centered data on arbitrary meshes. The TPFA Laplacian carries an implicit non-orthogonal correction (`"non-orthogonal correction"` option: `"over-relaxed"` or `"minimum"`) and gradients use a least-squares reconstruction, so both are exact on linear fields and second-order on skewed triangle and tetrahedral meshes. Diffusion coefficients reach faces through the distance-weighted harmonic mean, as in `FiniteVolume`, so material interfaces carry the exact series flux. ([#5688](https://github.com/pybamm-team/PyBaMM/pull/5688))
 - Added unstructured mesh support (`UnstructuredSubMesh`, generators, and interface coupling) for arbitrary 2D/3D domains. Hexahedra must have planar faces (warped hexes raise a `GeometryError`), and `UserSuppliedUnstructuredMesh` accepts tetrahedral, triangular, and quadrilateral cells only. ([#5687](https://github.com/pybamm-team/PyBaMM/pull/5687))

docs/source/api/models/lithium_ion/dfn.rst

@@ -13,4 +13,10 @@ Doyle-Fuller-Newman (DFN)
 .. autoclass:: pybamm.lithium_ion.BasicDFNHalfCell
     :members:
 
+.. autoclass:: pybamm.lithium_ion.BasicDFN2DUnstructured
+    :members:
+
+.. autoclass:: pybamm.lithium_ion.BasicDFN3DUnstructured
+    :members:
+
 .. footbibliography::

packages/pybamm/src/pybamm/__init__.py

@@ -168,7 +168,6 @@
     UserSuppliedSubmesh3D,
 )
 
-
 from .meshes.unstructured_submesh import (
     UnstructuredSubMesh,
     UnstructuredMeshGenerator,

packages/pybamm/src/pybamm/expression_tree/functions.py

@@ -719,8 +719,32 @@ def log10(child: pybamm.Symbol):
     return log(child, base=10)
 
 
-class Max(SpecificFunction):
-    """Max function."""
+class Reduction(SpecificFunction):
+    """Base class for reduction operations that collapse a spatial
+    field to a scalar (e.g. max, min).  Automatically clears domains
+    and returns scalar shape."""
+
+    def __init__(self, function: Callable, child: pybamm.Symbol):
+        super().__init__(function, child)
+        self.clear_domains()
+
+    @classmethod
+    def _from_json(cls, snippet: dict):
+        """See :meth:`pybamm.SpecificFunction._from_json()`.
+
+        ``SpecificFunction._from_json`` bypasses ``__init__``, so the domains
+        inherited from the child have to be cleared again here.
+        """
+        instance = super()._from_json(snippet)
+        instance.clear_domains()
+        return instance
+
+    def _evaluate_for_shape(self):
+        return np.nan * np.ones((1, 1))
+
+
+class Max(Reduction):
+    """Max function (reduction to scalar)."""
 
     def __init__(self, child):
         super().__init__(np.max, child)
@@ -750,8 +774,8 @@ def max(child: pybamm.Symbol):
     return pybamm.simplify_if_constant(Max(child))
 
 
-class Min(SpecificFunction):
-    """Min function."""
+class Min(Reduction):
+    """Min function (reduction to scalar)."""
 
     def __init__(self, child):
         super().__init__(np.min, child)

packages/pybamm/src/pybamm/expression_tree/symbol.py

@@ -45,12 +45,20 @@ def domain_size(domain: list[str] | str):
     fixed_domain_sizes = {
         "current collector": 3,
         "negative particle": 5,
+        "negative primary particle": 5,
+        "negative secondary particle": 5,
         "positive particle": 7,
+        "positive primary particle": 7,
+        "positive secondary particle": 7,
         "negative electrode": 11,
         "separator": 13,
         "positive electrode": 17,
         "negative particle size": 19,
+        "negative primary particle size": 19,
+        "negative secondary particle size": 19,
         "positive particle size": 23,
+        "positive primary particle size": 23,
+        "positive secondary particle size": 23,
     }
     if domain in [[], None]:
         size = 1

packages/pybamm/src/pybamm/models/full_battery_models/lithium_ion/__init__.py

@@ -24,6 +24,8 @@
 from .newman_tobias import NewmanTobias
 from .basic_dfn import BasicDFN
 from .basic_dfn_2d import BasicDFN2D
+from .basic_dfn_2d_unstructured import BasicDFN2DUnstructured
+from .basic_dfn_3d_unstructured import BasicDFN3DUnstructured
 from .basic_spm import BasicSPM
 from .basic_spm_with_3d_thermal import Basic3DThermalSPM
 from .basic_dfn_half_cell import BasicDFNHalfCell