.. _automatedMeshing:
Automated Meshing
*****************
Overview
========
Flow360 offers automated meshing, from CAD geometry to a surface mesh and finally to a volume mesh. The supported CAD format is \*.csm file which is Engineering Sketch Pad (EPS) format. The generated volume format is CGNS.
Geometry
========
The Engineering Sketch Pad is a solid-modeling, feature-based, web-enabled system for building parametric geometry.
It can be downloaded from `ESP's website `_.
Please check out pre-built ESP, you don't need to compile software from source.
The geometry in ESP is described in a text \*.csm file containing all CAD instructions. See csm example\:
.. code-block::
# Branches:
sphere 0 0 0 1
attribute groupName $mysphere
end
which will create a sphere of radius = 1 at (0, 0, 0). The sphere will be labelled as `mysphere`.
.. _fig1_geometry:
.. figure:: Figures/sphere_csm.png
:width: 50%
:align: center
Engineering Sketch Pad view of the geometry.
.. _ESPtoSurfaceMeshSection:
Surface Meshing
===============
The surface mesher takes the geometry file and configuration JSON file as input parameters and generates a surface mesh. The meshing configuration file (which can be defined as a dictionary in python), also called surfaceMesh.json, contains information such as maximum element edge length, curvature resolution angle or growth rate of 2D layers. See JSON example:
.. literalinclude:: Files/surfaceMesh.example.json
:language: JSON
The surface mesh is created by submitting a geometry file and JSON file using :code:`NewSurfaceMeshFromGeometry()` function. See the example below\:
.. code-block:: python
import flow360client
surfaceMeshId = flow360client.NewSurfaceMeshFromGeometry("path/to/geometry.csm", "surfaceMesh.json", surfaceMeshName="my_surface_mesh", solverVersion='release-22.2.3.0')
The above code will create a surface mesh of geometry using :code:`"maxEdgeLength": 0.05` on a surface labelled as `mysphere`, see line 4 of the \*.csm file.
.. _fig1_surfMesh:
.. figure:: Figures/sphere_surfMesh.png
:width: 50%
:align: center
Auto-generated surface mesh.
Inputs\:
- geometry.csm file
- surface mesh config.json (or defined as a dictionary in Python)
Outputs\:
- surface mesh
- :code:`surfaceMeshId`
For a full description of config.json for surface mesher see :ref:`here.`
.. _SurfaceToVolumeMeshSection:
Volume Meshing
==============
The volume mesher takes a :code:`surfaceMeshId` and a config JSON as arguments and generates a CGNS mesh suitable for the Flow360 solver. The JSON configuration file (or a dictionary in Python) specifies the first layer thickness, growth rate, sizes and location of refinement zones and actuator disks. All geometry from ESP is treated as a no-slip wall therefore prism layers will be grown off geometry surfaces.
The farfield will be created automatically\:
- cylindrical for quasi 3D cases if :code:`farfield->type: "quasi-3d"` is specified. Both sides of the farfield will be set as a symmetry boundary condition.
- semi-spherical if the geometry is bounded by :code:`y=0` plane. The :code:`y=0` plane will be set as a symmetry plane boundary condition.
- spherical otherwise.
Below is an example volume mesh JSON configuration:
.. literalinclude:: Files/volumeMesh.example.json
:language: JSON
The volume mesh is created by :code:`NewMeshFromSurface()` function using :code:`surfaceMeshId` and config.json. See the example below\:
.. code-block:: python
volumeMeshId = flow360client.NewMeshFromSurface(surfaceMeshId, "volumeMesh.json", meshName="my_volume_mesh")
The above code will create a volume mesh out of the surface mesh. The refinement zone of size=4x3x2 will be placed with its centre at (2,0,0). Additionally, it will be rotated by 45 degrees around the [0,0,1] axis. Spacing of 0.05 will be applied in this zone.
.. _fig1_volMesh:
.. figure:: Figures/sphere_volMesh.png
:width: 50%
:align: center
Auto-generated volume mesh.
Inputs\:
- :code:`surfaceMeshId`
- volume mesh config.json or python dict
Outputs\:
- volume CGNS mesh
- Flow360Mesh.json
- :code:`volumeMeshId`
For a full description of config.json for volume mesher see :ref:`here.`
.. _JSON surface mesher:
JSON surface mesher
===================
.. csv-table::
:file: Tables/surfaceMesher.csv
:header-rows: 1
:delim: @
:widths: 20 10 10 10 50
.. _JSON surface mesher edges:
edges
-----
.. csv-table::
:file: Tables/surfaceMesherEdges.csv
:header-rows: 1
:delim: @
:widths: 20 10 10 10 50
Example\:
.. code-block:: json
"edges": {
"leadingEdge": {
"type": "aniso",
"method": "angle",
"value": 1
},
"trailingEdge": {
"type": "aniso",
"method": "height",
"value": 1e-3
},
"hubCircle": {
"type": "aniso",
"method": "height",
"value": 0.1
},
"hubSplitEdge": {
"type": "projectAnisoSpacing"
}
}
.. _fig1_surfMesh_edges:
.. figure:: Figures/surfaceMesh_firstLayerThickness.png
:width: 50%
:align: center
Surface mesh of a wing. Leading edge and trailing edge are labelled and first layer thickness is applied to the layers grown from the edges.
.. _fig_surfMesh_edges_projectAnisoSpacing:
.. figure:: Figures/projectAnisoSpacing.png
:width: 70%
:align: center
Example of edge type "projectAnisoSpacing". See the above JSON example: "hubCircle" colored green, "hubSplitEdge" colored red which is of type "projectAnisoSpacing". The anisotropic spacing on the neighboring patches will be “projected” to the edge, i.e., the nodes distribution along the edge will be updated.
.. _JSON surface mesher faces:
faces
-----
.. csv-table::
:file: Tables/surfaceMesherFaces.csv
:header-rows: 1
:delim: @
:widths: 20 10 10 10 50
Example\:
.. code-block:: json
"faces": {
"rightWing": {
"maxEdgeLength": 0.05
},
"fuselage": {
"maxEdgeLength": 0.05
}
}
.. _JSON volume mesher:
JSON volume mesher
==================
.. csv-table::
:file: Tables/volumeMesher.csv
:header-rows: 1
:delim: @
:widths: 20 14 6 12 50
Gap treatment examples\:
.. _fig_gaptreatment0:
.. figure:: Figures/gap0.png
:width: 55%
:align: center
Default configuration, :code:`gapTreatmentStrength=0`
.. _fig_gaptreatment025:
.. figure:: Figures/gap025.png
:width: 55%
:align: center
:code:`gapTreatmentStrength=0.25`
.. _fig_gaptreatment050:
.. figure:: Figures/gap050.png
:width: 55%
:align: center
:code:`gapTreatmentStrength=0.5`
.. _fig_gaptreatment075:
.. figure:: Figures/gap075.png
:width: 55%
:align: center
:code:`gapTreatmentStrength=0.75`
.. _fig_gaptreatment100:
.. figure:: Figures/gap100.png
:width: 55%
:align: center
:code:`gapTreatmentStrength=1.0`
The larger :code:`gapTreatmentStrength` is, the more space is dedicated to isotropic mesh than anisotropic mesh in narrow gaps.
.. _JSON volume mesher refinement:
refinement (list)
-----------------
.. csv-table::
:file: Tables/volumeMesherRefinement.csv
:header-rows: 1
:delim: @
:widths: 16 10 14 10 50
Example\:
.. code-block:: json
"refinement": [
{
"size": [4, 3, 2],
"center": [2, 0, 0],
"spacing": 0.05,
"axisOfRotation": [ 0, 0, 1 ],
"angleOfRotation": 45
},
{
"type": "cylinder",
"radius": 4,
"length": 5,
"center": [5, 0, 0],
"spacing": 0.05,
"axis": [1, 0, 0]
}]
.. _JSON volume mesher rotorDisks:
rotorDisks (list)
------------------
.. csv-table::
:file: Tables/volumeMesherRotorDisks.csv
:header-rows: 1
:delim: @
:widths: 20 10 10 10 50
Example\:
.. code-block:: json
"rotorDisks": [
{
"name": "enclosed",
"innerRadius": 0,
"outerRadius": 0.75,
"thickness": 0.1,
"axisThrust": [1, 0, 0],
"center": [0, 5.0, 0],
"spacingAxial": 0.1,
"spacingRadial": 0.1,
"spacingCircumferential": 0.1
},
{
"innerRadius": 0,
"outerRadius": 0.75,
"thickness": 0.1,
"axisThrust": [0, 0, 1],
"center": [0, -5, 0],
"spacingAxial": 0.1,
"spacingRadial": 0.1,
"spacingCircumferential": 0.1
}
],
.. _JSON volume mesher slidingInterfaces:
slidingInterfaces (list)
------------------------
.. csv-table::
:file: Tables/volumeMesherSlidingInterfaces.csv
:header-rows: 1
:delim: @
:widths: 20 12 10 10 48
Example\:
.. code-block:: json
"slidingInterfaces": [
{
"name": "inner",
"innerRadius": 0,
"outerRadius": 0.75,
"thickness": 0.5,
"axisOfRotation": [0, 0, 1],
"center": [0, 0, 0],
"spacingAxial": 0.2,
"spacingRadial": 0.2,
"spacingCircumferential": 0.2,
"enclosedObjects": ["hub", "blade1", "blade2", "blade3"]
}, {
"name": "mid",
"innerRadius": 0,
"outerRadius": 2.0,
"thickness": 2.0,
"axisOfRotation": [0, 1, 0],
"center": [0, 0, 0],
"spacingAxial": 0.2,
"spacingRadial": 0.2,
"spacingCircumferential": 0.2,
"enclosedObjects": ["slidingInterface-inner"]
}, {
"innerRadius": 0,
"outerRadius": 2.0,
"thickness": 2.0,
"axisOfRotation": [0, 1, 0],
"center": [0, 5, 0],
"spacingAxial": 0.2,
"spacingRadial": 0.2,
"spacingCircumferential": 0.2,
"enclosedObjects": ["rotorDisk-enclosed"]
}, {
"innerRadius": 1.5,
"outerRadius": 2.0,
"thickness": 2.0,
"axisOfRotation": [0, 1, 0],
"center": [0, -5, 0],
"spacingAxial": 0.2,
"spacingRadial": 0.2,
"spacingCircumferential": 0.2,
"enclosedObjects": []
}, {
"name": "outer",
"innerRadius": 0,
"outerRadius": 8,
"thickness": 6,
"axisOfRotation": [1, 0, 0],
"center": [0, 0, 0],
"spacingAxial": 0.4,
"spacingRadial": 0.4,
"spacingCircumferential": 0.4,
"enclosedObjects": ["slidingInterface-mid", "rotorDisk-1", "slidingInterface-2", "slidingInterface-3"]
}
],
.. _fig_slidingInterfaces:
.. figure:: Figures/slidingInterfaces.png
:width: 90%
:align: center
Rotor disks and sliding interfaces generated according to the above configuration.