feat: get mesh by zone name or id (#3638)

* feat: Add field_data.get_zones_info()

* feat: get mesh by zone name

* feat: get mesh by zone name

* feat: get mesh by zone name

* feat: fix circular reference issue

Author: mkundu1

src/ansys/fluent/core/services/field_data.py

@@ -5,6 +5,7 @@
 from functools import reduce
 import io
 from typing import Callable, Dict, List, Tuple
+import weakref
 
 import grpc
 import numpy as np
@@ -954,6 +955,36 @@ def _extract_field(field_datatype, field_size, chunk_iterator):
         return fields_data
 
 
+# Root domain id in Fluent.
+ROOT_DOMAIN_ID = 1
+
+
+class ZoneType(Enum):
+    """Zone types for mesh."""
+
+    CELL = 1
+    FACE = 2
+
+
+@dataclass
+class ZoneInfo:
+    """Zone information for mesh.
+
+    Attributes:
+    -----------
+    _id : int
+        Zone ID.
+    name : str
+        Name of the zone.
+    zone_type : ZoneType
+        Type of the zone for mesh.
+    """
+
+    _id: int
+    name: str
+    zone_type: ZoneType
+
+
 @dataclass
 class Node:
     """Node class for mesh.
@@ -1062,12 +1093,14 @@ def __init__(
         field_info: FieldInfo,
         is_data_valid: Callable[[], bool],
         scheme_eval=None,
+        get_zones_info: weakref.WeakMethod[Callable[[], list[ZoneInfo]]] | None = None,
     ):
         """__init__ method of FieldData class."""
         self._service = service
         self._field_info = field_info
         self.is_data_valid = is_data_valid
         self.scheme_eval = scheme_eval
+        self.get_zones_info = lambda: get_zones_info()()
 
         self._allowed_surface_names = _AllowedSurfaceNames(field_info)
 
@@ -1417,28 +1450,45 @@ def get_pathlines_field_data(
             }
         return path_lines_dict
 
-    def get_mesh(self, zone_id: int) -> Mesh:
+    def get_mesh(self, zone: str | int) -> Mesh:
         """Get mesh for a zone.
 
         Parameters
         ----------
-        zone_id : int
-            Zone ID.
+        zone : str | int
+            Zone name or id. Currently, only cell zones are supported.
 
         Returns
         -------
         Mesh
             Mesh object containing nodes and elements.
+
+        Raises
+        ------
+        ValueError
+            If the zone is not found.
+        NotImplementedError
+            If a face zone is provided.
         """
+        zone_info = None
+        for zone_info in self.get_zones_info():
+            if zone_info.name == zone or zone_info._id == zone:
+                break
+        if zone_info is None:
+            raise ValueError(f"Zone {zone} not found.")
+        if zone_info.zone_type == ZoneType.FACE:
+            raise NotImplementedError("Face zone mesh is not supported.")
+
+        # Mesh data is retrieved from the root domain in Fluent
         request = FieldDataProtoModule.GetSolverMeshNodesRequest(
-            domain_id=1, thread_id=zone_id
+            domain_id=ROOT_DOMAIN_ID, thread_id=zone_info._id
         )
         response = self._service.get_solver_mesh_nodes(request)
         nodes = response.nodes
         nodes = [Node(_id=node.id, x=node.x, y=node.y, z=node.z) for node in nodes]
         nodes = sorted(nodes, key=lambda x: x._id)
         request = FieldDataProtoModule.GetSolverMeshElementsRequest(
-            domain_id=1, thread_id=zone_id
+            domain_id=ROOT_DOMAIN_ID, thread_id=zone_info._id
         )
         response = self._service.get_solver_mesh_elements(request)
         elements_pb = response.elements

src/ansys/fluent/core/session.py

@@ -3,15 +3,15 @@
 from enum import Enum
 import json
 import logging
-from typing import Any, Dict
+from typing import Any, Callable, Dict
 import warnings
 import weakref
 
 from ansys.fluent.core.fluent_connection import FluentConnection
 from ansys.fluent.core.journaling import Journal
 from ansys.fluent.core.services import service_creator
 from ansys.fluent.core.services.app_utilities import AppUtilitiesOld
-from ansys.fluent.core.services.field_data import FieldDataService
+from ansys.fluent.core.services.field_data import FieldDataService, ZoneInfo
 from ansys.fluent.core.services.scheme_eval import SchemeEval
 from ansys.fluent.core.streaming_services.datamodel_event_streaming import (
     DatamodelEvents,
@@ -85,6 +85,7 @@ class BaseSession:
         Close the Fluent connection and exit Fluent.
     """
 
+    # We are passing around an WeakMethod to avoid circular references
     def __init__(
         self,
         fluent_connection: FluentConnection,
@@ -93,6 +94,7 @@ def __init__(
         start_transcript: bool = True,
         launcher_args: Dict[str, Any] | None = None,
         event_type: Enum | None = None,
+        get_zones_info: weakref.WeakMethod[Callable[[], list[ZoneInfo]]] | None = None,
     ):
         """BaseSession.
 
@@ -120,6 +122,7 @@ def __init__(
             scheme_eval,
             file_transfer_service,
             event_type,
+            get_zones_info,
         )
 
     def _build_from_fluent_connection(
@@ -128,6 +131,7 @@ def _build_from_fluent_connection(
         scheme_eval: SchemeEval,
         file_transfer_service: Any | None = None,
         event_type=None,
+        get_zones_info: weakref.WeakMethod[Callable[[], list[ZoneInfo]]] | None = None,
     ):
         """Build a BaseSession object from fluent_connection object."""
         self._fluent_connection = fluent_connection
@@ -205,6 +209,7 @@ def __init__(self, _session):
                     self.field_info,
                     self._is_solution_data_valid,
                     _session.scheme_eval,
+                    get_zones_info,
                 )
                 self.field_data_streaming = FieldDataStreaming(
                     _session._fluent_connection._id, _session._field_data_service

src/ansys/fluent/core/session_solver.py

@@ -6,9 +6,12 @@
 import threading
 from typing import Any, Dict
 import warnings
+import weakref
 
+from ansys.api.fluent.v0 import svar_pb2 as SvarProtoModule
 import ansys.fluent.core as pyfluent
 from ansys.fluent.core.services import SchemeEval, service_creator
+from ansys.fluent.core.services.field_data import ZoneInfo, ZoneType
 from ansys.fluent.core.services.reduction import ReductionService
 from ansys.fluent.core.services.solution_variables import (
     SolutionVariableData,
@@ -106,6 +109,7 @@ def __init__(
             start_transcript=start_transcript,
             launcher_args=launcher_args,
             event_type=SolverEvent,
+            get_zones_info=weakref.WeakMethod(self._get_zones_info),
         )
         self._build_from_fluent_connection(fluent_connection, scheme_eval)
 
@@ -176,6 +180,23 @@ def svar_info(self):
         )
         return self.fields.solution_variable_info
 
+    def _get_zones_info(self) -> list[ZoneInfo]:
+        zones_info = []
+        for (
+            zone_info
+        ) in self.fields.solution_variable_info.get_zones_info()._zones_info.values():
+            zone_type = (
+                ZoneType.CELL
+                if zone_info.thread_type == SvarProtoModule.ThreadType.CELL_THREAD
+                else ZoneType.FACE
+            )
+            zones_info.append(
+                ZoneInfo(
+                    _id=zone_info.zone_id, name=zone_info.name, zone_type=zone_type
+                )
+            )
+        return zones_info
+
     @property
     def reduction(self):
         """``Reduction`` handle."""

tests/test_field_data.py

@@ -9,6 +9,7 @@
     CellElementType,
     FieldUnavailable,
     SurfaceDataType,
+    ZoneType,
 )
 
 HOT_INLET_TEMPERATURE = 313.15
@@ -472,9 +473,41 @@ def plot_mesh(index, field_name, data):
 
 
 @pytest.mark.fluent_version(">=25.2")
-def test_mesh_data(static_mixer_case_session):
+def test_mesh_data_2d_standard(disk_case_session):
+    solver = disk_case_session
+    zones_info = solver.fields.field_data.get_zones_info()
+    cell_zone_names = [z.name for z in zones_info if z.zone_type == ZoneType.CELL]
+    face_zone_names = [z.name for z in zones_info if z.zone_type == ZoneType.FACE]
+    assert cell_zone_names == ["fluid-7"]
+    assert face_zone_names == [
+        "velocity-inlet-2",
+        "pressure-outlet-3",
+        "interior-4",
+        "axis-5",
+        "wall-6",
+    ]
+    mesh = solver.fields.field_data.get_mesh(zone="fluid-7")
+    assert len(mesh.nodes) == 6351
+    assert len(mesh.elements) == 6192
+    assert mesh.elements[0].element_type == CellElementType.QUADRILATERAL
+    assert len(mesh.elements[0].node_indices) == 4
+    assert min(mesh.nodes, key=lambda x: x.x).x == pytest_approx(0.0)
+    assert max(mesh.nodes, key=lambda x: x.x).x == pytest_approx(0.06202)
+    assert min(mesh.nodes, key=lambda x: x.y).y == pytest_approx(0.0)
+    assert max(mesh.nodes, key=lambda x: x.y).y == pytest_approx(0.443)
+    assert min(mesh.nodes, key=lambda x: x.z).z == pytest_approx(0.0)
+    assert max(mesh.nodes, key=lambda x: x.z).z == pytest_approx(0.0)
+
+
+@pytest.mark.fluent_version(">=25.2")
+def test_mesh_data_3d_poly(static_mixer_case_session):
     solver = static_mixer_case_session
-    mesh = solver.fields.field_data.get_mesh(zone_id=97)
+    zones_info = solver.fields.field_data.get_zones_info()
+    cell_zone_names = [z.name for z in zones_info if z.zone_type == ZoneType.CELL]
+    face_zone_names = [z.name for z in zones_info if z.zone_type == ZoneType.FACE]
+    assert cell_zone_names == ["fluid"]
+    assert face_zone_names == ["inlet1", "inlet2", "outlet", "wall", "interior--fluid"]
+    mesh = solver.fields.field_data.get_mesh(zone="fluid")
     assert len(mesh.nodes) == 82247
     assert len(mesh.elements) == 22771
     assert mesh.elements[0].element_type == CellElementType.POLYHEDRON