Adaptive Mesh Refinement by Air Shaper - Revision history

Jozsef Nagy at 10:26, 4 October 2022

2022-10-04T10:26:45Z

Jozsef Nagy at 04:43, 17 June 2021

2021-06-17T04:43:57Z

Jozsef Nagy: /* Results */

2021-06-15T05:12:24Z

Results

Jozsef Nagy: /* Results */

2021-06-15T05:09:31Z

Results

Jozsef Nagy at 05:07, 15 June 2021

2021-06-15T05:07:35Z

Jozsef Nagy: /* Results */

2021-06-11T07:09:33Z

Results

Jozsef Nagy: /* Results */

2021-06-11T07:05:03Z

Results

Jozsef Nagy at 07:01, 11 June 2021

2021-06-11T07:01:12Z

Jozsef Nagy at 07:00, 11 June 2021

2021-06-11T07:00:41Z

Jozsef Nagy: Created page with "category:mesh * '''contributor''': Nikola Majksner and Wouter Remmerie * '''affiliation''': Air Shaper * '''contact''': * '''affiliation''': Air Shaper
* '''contact''': <mail address='nikola@airshaper.com' description='author'>click here for email address</mail>, <mail address='wouter@airshaper.com' description='author'>click here for email address</mail>
* '''OpenFOAM versions''': v2012
* '''Published under''': CC BY-NC-ND license ([https://creativecommons.org/licenses creative commons licenses])

Go back to [https://wiki.openfoam.com/Collection_by_authors Collection by authors].

Go back to [https://wiki.openfoam.com/Meshing Meshing].

=[https://github.com/airshaper/adaptive-mesh-refinement.git Adaptive Mesh Refinement]=

OpenFOAM motorBike case with adaptive volume & surface mesh refinement based on curl(U) or grad(p)

== Description ==

This repository provides adaptive mesh refinement for both the volume mesh and the surface mesh. Any field can be used for refinement. In this tutorial, two options have been included:

<ul>
<li>grad(p): the pressure gradient</li>
<li>curl(U): the curl of the velocity field
Both are multipled by the cell length to “discourage” the algorithm to keep refining the smallest cells. The method has 3 major parts:</li></ul>

<ol style="list-style-type: decimal;">
<li>Initial mesh
SnappyHexMesh is run in two separate steps:
<ul>
<li>castellated mesh: only runs the refinement phase using “baffles” for the surface of the geometry (to avoid the mesh inside the geometry being cut and to keep all cells hexagonal). This mesh is stored in <code>primal_refinement</code> for use in the mesh refinement phase.</li>
<li>snapping phase: this part will cut the mesh (by also having castellated enabled) and snap it to the surface (by setting the surface patch type to <code>wall</code>). This mesh is used in <code>primal_run</code> for the first CFD loop.</li></ul>
</li>
<li>Refinement field
Once the first CFD loop has finished, it maps the fields onto the stored castellated mesh (in <code>primal_refinement</code>) and calculates the refinement field (<code>refVal</code>), for which the lower limit value should be set manually in <code>primal_refinement/constant/dynamicMeshDict</code>.</li>
<li>Mesh refinement
The refinement is then applied to the castellated mesh of the first loop. Once refinement is done, the castellated mesh is copied to <code>primal_run</code> where the snapping phase is executed again to snap the refined mesh to the surface. This mesh is then used for the second and final CFD run.</li></ol>

== Conclusions ==

This method allows for mesh refinement of both the volume and the surface mesh.

In contrast to other OpenFOAM® based methods that refine on the surface, the mesh is re-snapped after refinement, which improves the correspondence to the real geometry.

Adaptive mesh refinement can greatly reduce the computational cost, as the mesh is applied in a more efficient way.

Any given field can be created to steer the mesh refinement. The gradient of pressure (useful for airfoils for example) and curl of the velocity field (useful for wake refinement for example) have been included.

We definitely welcome any contribution to further improve this method (for example, would it be easier to just use refineMesh instead of pimpleFoam?).

== How to run the case ==

# Make sure you have installed latest [https://www.openfoam.com/download/ OpenFOAM v2012]
# Clone this repository on your machine <code>git clone https://github.com/airshaper/adaptive-mesh-refinement.git</code>
# Adopt <code>primal_run/system/decomposeParDict</code> depending on number of cores you have. Change <code>numberOfSubdomains 6</code> to number of cores or threads you have available. Also modify <code>n</code> under <code>coeffs</code> to reflect <code>numberOfSubdomains</code> change. For example if you have 12 cores your <code>n</code> should be <code>(3 2 2)</code> if you have 16 cores for example then <code>n</code> should be <code>(4 2 2)</code> and so on.
# Go to <code>cd ./primal_run</code> then run <code>./Allrun</code>

== Results ==

Non-refined mesh slice [[File:images/motorBike_before_refinement_slice.png?raw=true|Non-refined mesh]]

Refined mesh slice with curl(U) (notice how curl(U) refines the wake as well) [[File:images/motorBike_after_refinement_slice_curlU.png?raw=true|Refined Mesh with curl(U)]]

Refined mesh slice with grad(p) (notice how grad(p) mostly refines the surface) [[File:images/motorBike_after_refinement_slice_gradp.png?raw=true|Refined Mesh with grad(p)]]

Zoomed Non-refined mesh slice [[File:images/motorBike_before_refinement_slice_zoomed.png?raw=true|Zoomed Non-refined mesh]]

Zoomed Refined mesh slice with curl(U) [[File:images/motorBike_after_refinement_slice_zoomed_curlU.png?raw=true|Zoomed Refined Mesh with curl(U)]]

Zoomed Refined mesh slice with grad(p) [[File:images/motorBike_after_refinement_slice_zoomed_gradp.png?raw=true|Zoomed Refined Mesh with grad(p)]]

Non-refined surface mesh [[File:images/motorBike_before_refinement_surface.png?raw=true|Non-refined surface mesh]]

Refined surface mesh based on curl(U) [[File:images/motorBike_after_refinement_surface_curlU.png?raw=true|Refined surface mesh based on curl(U)]]

Refined surface mesh based on grad(p) [[File:images/motorBike_after_refinement_surface_gradp.png?raw=true|Refined surface mesh based on grad(p)]]

Custom calculated field refVal based on curl(U) [[File:images/motorBike_before_refinement_slice_refVal_curlU.png?raw=true|Custom calculated field refVal based on curl(U)]]

Custom calculated field refVal based on grad(p) [[File:images/motorBike_before_refinement_slice_refVal_gradp.png?raw=true|Custom calculated field refVal based on grad(p)]]

@@ Line 34: / Line 34: @@
 <li><p>Mesh refinement</p>
 <p>The refinement is then applied to the castellated mesh of the first loop. Once refinement is done, the castellated mesh is copied to <code>primal_run</code> where the snapping phase is executed again to snap the refined mesh to the surface. This mesh is then used for the second and final CFD run.</p></li></ol>
 == Conclusions ==

@@ Line 78: / Line 78: @@
 Zoomed Refined mesh slice with grad(p)
-[[File:AS_motorBike_after_refinement_slice_zoomed_gradp2.png|650px|center|Zoomed Refined Mesh with grad(p)]]
+[[File:AS_motorBike_after_refinement_slice_zoomed_gradp.png|650px|center|Zoomed Refined Mesh with grad(p)]]
 Non-refined surface mesh

@@ Line 76: / Line 76: @@
 [[File:AS_motorBike_after_refinement_slice_zoomed_curlU.png|650px|center|Zoomed Refined Mesh with curl(U)]]
-Zoomed Refined mesh slice with grad(p) [[File:AS_motorBike_after_refinement_slice_zoomed_gradp.png|650px|center|Zoomed Refined Mesh with grad(p)]]
+Zoomed Refined mesh slice with grad(p)
 Non-refined surface mesh

@@ Line 58: / Line 58: @@
 Non-refined mesh slice [[File:images/motorBike_before_refinement_slice.png?raw=true|Non-refined mesh]]
-Refined mesh slice with curl(U) (notice how curl(U) refines the wake as well) [[File:AS_MotorBike_after_refinement_slice_curlU.png?raw=true|Refined Mesh with curl(U)]]
+Refined mesh slice with curl(U) (notice how curl(U) refines the wake as well) [[File:AS_MotorBike_after_refinement_slice_curlU.png|Refined Mesh with curl(U)]]
 Refined mesh slice with grad(p) (notice how grad(p) mostly refines the surface) [[File:images/motorBike_after_refinement_slice_gradp.png?raw=true|Refined Mesh with grad(p)]]

@@ Line 3: / Line 3: @@
 * '''affiliation''': [https://airshaper.com AirShaper]
 * '''contact''': <mail address='nikola@airshaper.com' description='author'>click here for email address</mail>, <mail address='wouter@airshaper.com' description='author'>click here for email address</mail>
-* '''OpenFOAM versions''': v2012
+* '''OpenFOAM versions''': v2206
 * '''Published under''': CC BY-NC-ND license ([https://creativecommons.org/licenses creative commons licenses])

@@ Line 1: / Line 1: @@
 [[category:mesh]]
 * '''contributor''': Nikola Majksner and Wouter Remmerie
-* '''affiliation''': Air Shaper
+* '''affiliation''': [https://airshaper.com AirShaper]
 * '''contact''': <mail address='nikola@airshaper.com' description='author'>click here for email address</mail>, <mail address='wouter@airshaper.com' description='author'>click here for email address</mail>
 * '''OpenFOAM versions''': v2012

@@ Line 56: / Line 56: @@
 == Results ==
-Non-refined mesh slice [[File:images/motorBike_before_refinement_slice.png?raw=true|Non-refined mesh]]
+Non-refined mesh slice
 Refined mesh slice with curl(U) (notice how curl(U) refines the wake as well)
@@ Line 66: / Line 68: @@
 [[File:AS_motorBike_after_refinement_slice_gradp.png|650px|center|Refined Mesh with grad(p)]]
-Zoomed Non-refined mesh slice [[File:images/motorBike_before_refinement_slice_zoomed.png?raw=true|Zoomed Non-refined mesh]]
+Zoomed Non-refined mesh slice
 Zoomed Refined mesh slice with curl(U)
@@ Line 74: / Line 78: @@
 Zoomed Refined mesh slice with grad(p) [[File:AS_motorBike_after_refinement_slice_zoomed_gradp.png|650px|center|Zoomed Refined Mesh with grad(p)]]
-Non-refined surface mesh [[File:images/motorBike_before_refinement_surface.png?raw=true|Non-refined surface mesh]]
+Non-refined surface mesh
-Refined surface mesh based on curl(U) [[File:images/motorBike_after_refinement_surface_curlU.png?raw=true|Refined surface mesh based on curl(U)]]
+Custom calculated field refVal based on curl(U)
-Refined surface mesh based on grad(p) [[File:images/motorBike_after_refinement_surface_gradp.png?raw=true|Refined surface mesh based on grad(p)]]
+[[File:AS_motorBike_before_refinement_slice_refVal_curlU.png|650px|center|Custom calculated field refVal based on curl(U)]]
-Custom calculated field refVal based on curl(U) [[File:images/motorBike_before_refinement_slice_refVal_curlU.png?raw=true|Custom calculated field refVal based on curl(U)]]
+Custom calculated field refVal based on grad(p)
-Custom calculated field refVal based on grad(p) [[File:images/motorBike_before_refinement_slice_refVal_gradp.png?raw=true|Custom calculated field refVal based on grad(p)]]
+[[File:AS_motorBike_before_refinement_slice_refVal_gradp.png|650px|center|Custom calculated field refVal based on grad(p)]]