feat: Retrieve mesh data in solution mode

[mkundu1]

import pyvista as pv
import numpy as np
import ansys.fluent.core as pyfluent
from ansys.fluent.core.services.field_data import CellElementType

def convert_fluent_element_type_to_pv_cell_type(element_type):
    if element_type == CellElementType.TETRAHEDRON:
        return pv.CellType.TETRA
    if element_type == CellElementType.HEXAHEDRON:
        return pv.CellType.HEXAHEDRON
    # Add other element types
    raise ValueError(f"Unknown element type {element_type}")

solver = pyfluent.launch_fluent(processor_count=4)
solver.settings.file.read_case(file_name="d:/work/elbow.cas.h5")
mesh = solver.fields.field_data.get_mesh(zone_id=2)
points = np.array([(node.x, node.y, node.z) for node in mesh.nodes])
cells = np.array([[len(element.node_indices)] + element.node_indices for element in mesh.elements]).ravel()
cell_types = [convert_fluent_element_type_to_pv_cell_type(element.element_type) for element in mesh.elements]
grid = pv.UnstructuredGrid(cells, cell_types, points)
pv.plot(grid, show_edges=True)

[mkundu1]

We shall have FaceElementType when we support that in future.

[mkundu1]

Connectivity for polyhedral cells is not yet properly supported. This class will be bit more complex when we support that in future.

[mkundu1]

TODO: It would be more performant to do the 0-based indexing and sorting in the server-side. Maybe we can eliminate ids at the protobuf layer also.

[mkundu1]

I have noted down the future tasks for this feature: #3585 (comment)