# Workshop 2 Session 1 Homework: Optimization of a wing - Part I Meshing

## Homework submission

Submitting all three homework assignments will qualify you for a free Professional Training (value of 500€) as well as a certificate of participation.

Homework 1 - Deadline Date 09/29 at 12pm

Submission Form

## Exercise

The task is to optimize an aircraft wing with and without winglet. The two geometries are as shown below.

For these cases we will use the “Hex-Dominant Parametric” meshing operation which provides full functionality to mesh complex geometries. The Tutorial below will provide detailed steps on how to use each meshing feature to get a well resolved mesh.

## Step-by-Step

Import the project by clicking the link below. ( Crtl + Click to open in a new tab )

Click to Import the Homework Project

Once the project is imported, the workbench is automatically opened. Then follow the steps below for setting up an incompressible flow simulation.

### Geometry

Note: The imported geometry has pre-created ‘Topological sets’ for some essential geometry faces. These sets will be later used for mesh refinements.

The created Sets are shown in the figure below, you can click to highlight the set in red.

### Creating a Mesh

• Select the geometry and click on ‘New Mesh’ button to create a new mesh operation as shown.

#### Main Settings

• In the Main Settings , select “Hex-Dominant Parametric (only CFD)” . Then specify the following parameters and click the Save button.

Number of cells in X-direction: 120
Number of cells in Y-direction: 100
Number of cells in Z-direction: 30

Number of computing processors: 16 ( Please note this has been updated 29-09-16 to avoid errors )

• After saving the tree is extend with 2 new entries, called ‘BaseMeshBox’ and ‘Material Point’ which must be defined.

#### Geometry Primitives

Base Mesh Box

The ‘Base Mesh Box’ defines the outer flow domain boundaries. This must be significantly larger for external flow. Enter the values as shown and click Save.

Min X= -90
Min Y= -100
Min Z= 0.001
Max X= 150
Max Y= 100
max Z= 60

Material Point
The ‘Material Point’ specifies the region that will be meshed. So in this case the point must be out side the aircraft body.
Enter the values as shown and click Save.

Center X= 4
Center Y= 3.3
Center Z= 3

#### Further primitives

• We will create 4 entities that will be used for mesh region refinements later in the meshing setup.
• To create a New entity, click on ‘Geometry Primitives’ and then the ‘New’ button on top to select a ‘Cylinder’ entity.

The table details the parameters for the 4 cylinder entities that are shown in the figures below.

.

Outer-region

Inner-region

Wing-tip-region

Wing-tip-region 2

#### Mesh Refinements

We will now add the necessary mesh refinements for the previously created geometry sets and the geometry primitives.

• Click on ‘Mesh Refinements’ and click ‘New’ button to add a refinement.

#### Surface refinements

• This refinement will used to refine the bigger surfaces of the wing.

Select the settings as follows and click Save.
Name: Surface-wing
Type : Surface refinement
Level Min : 6
Level Max : 7
Assigned entity Type: Faces
Name: ‘shell_0_face_0’, 'shell_0_face_2’

.

• This refinement will used to refine the small surface of the wing.

Select the settings as follows and click Save.
Name: Surface-edges
Type : Surface refinement
Level Min : 9
Level Max : 9
Assigned entity Type: Faces
Name: 'shell_0_face_1’

.

#### Region refinements

These refinements will refine the volume mesh. We will create 3 region refinements and assign them the previously created geometry primitives.

• So create a new ‘Mesh Refinement’ .
• and enter the settings as follows:Wing-tip-region****Wing-tip-region
Name: Region - 1
Type : Region refinement
Mode : Inside
Distance : 1
Level : 2
Assigned geometry primitives: Outer-region

.
Name: Region - 2
Type : Region refinement
Mode : Inside
Distance : 1
Level : 3
Assigned geometry primitives: Inner-region, Wing-tip-region

.
Name: Region - 3
Type : Region refinement
Mode : Inside
Distance : 1
Level : 4
Assigned geometry primitives: Wing-tip-region 2

#### Feature refinement

The feature refinement will refine near edges. This is important to capture sharp corners.

• So Add a New ‘Mesh Refinement’, and choose Type as ‘Feature Refinement’. Give a Distance of 0 and a Level of 6.

#### Layer refinement

The layer refinement is important to capture the boundary layer near the wall. This will create layer cells following the surface curvature near the walls.

• So Add a New ‘Mesh Refinement’, and choose Type as ‘Layer addition’. Change ‘Number of layers’ to 4, ‘expansionRatio’ to 1.65 and ‘minThickness’ to 0.001
• Then select all the surfaces ‘shell_0_face_0’, ‘shell_0_face_1’ and ‘shell_0_face_2’, and click Save.

Lastly, we will change a few parameters in the Advance Settings by clicking on the mesh operation and scrolling in the settings panel as shown in figures below. This will help to get a good quality mesh for a complex geometry and get the appropriate y-plus value for the cases.

• Only the highlighted parameters need to be changed to the shown value.

Finally, click Save.

Start the Meshing Operation

To Start the mesh operation click on the Start button at the top.

Please Note: Parallel compute cores are changed to 16 to avoid errors

• The completed mesh looks as follows.

### Mesh-2 (Aircraft - blended winglet)

• For the second mesh, please follow the same procedures as the previous case till the creation of ‘Geometry primitives’. In this the geometry Aircraft blended winglet geometry is selected to create the mesh. The viewer should look as shown below.

The table details the parameters for the 4 cylinder entities that are shown in the figures below.

Note that the change is only in geometry primitives Wing-tip-region and Wing-tip-region 2

Wing-tip-region

Wing-tip-region 2

#### Mesh refinements

The mesh refinements are to be done as follows.

Surface-wing

Select the settings as follows and click Save.
Name: Surface-wing
Type : Surface refinement
Level Min : 6
Level Max : 7
Assigned entity Type: Face sets
Name: 'Wing’

Surface-edges

Select the settings as follows and click Save.
Name: Surface-edges
Type : Surface refinement
Level Min : 9
Level Max : 9
Assigned entity Type: Face sets
Name: 'edges-wing’

• The region refinements are same as the previous mesh. Please define the 3 regions as for the wing case.

Layer

• Add a New ‘Mesh Refinement’, and choose Type as ‘Layer Refinement’. Change ‘Number of layers’ to 4, ‘expansionRatio’ to 1.65 and ‘minThickness’ to 0.001
• Then select all the face sets and click Save.

Surface-winglet

Select the settings as follows and click Save.
Name: Surface-winglet
Type : Surface refinement
Level Min : 7
Level Max : 8
Assigned entity Type: Face sets
Name: ‘Winglet’ and 'winglet-tip’

Surface-winglet-edges

Select the settings as follows and click Save.
Name: Surface-winglet-edges
Type : Surface refinement
Level Min : 10
Level Max : 10
Assigned entity Type: Face sets
Name: 'edges-winglet’

• That’s all. Once done click the ‘Start’ button to begin the meshing operation.

#### Once done with the Meshing, follow Homework Part-II (Click) for the Simulation Setup.

2 Likes

Hi,

Please find bellow some learning resources and books about airfoil theory and CFD

## Books:

Theory of Wing Sections: Including a Summary of Airfoil Data, Ira H. Abbott
Computational Fluid Dynamics: A Practical Approach, Jiyuan Tu

## Videos:

How do Wings generate Lift?

Introduction to CFD

10 Likes

The best explanation i’ve ever seen of how an airfoil generates lift! So detailed and consistently. None of my university lecturers in fluid dynamics couldn’t explain it so clearly.

6 Likes

In the step for “Layer refinement”, the option for type is “Layer addition”, not ‘Layer Refinement’. Although it is a minor mistake, it got me a few seconds to realize and I’m writing this so that others can confirm their doubt, specially the beginners.
And thank you so much Simscale for this platform, loved every bit of it, right from the webminars and workshops to the projects.

Hey @alamtania,

Thanks for pointing this! I’ve made the change.
Great to hear your interest for SimScale

Sam

1 Like

Hi guys,

Is it good if I add the same Advanced Settings of the Wing mesh to the Blended Winglet mesh, to obtain better results???
And should we create in the Blended Winglet mesh a Feature Refinement, as we did for the Wing mesh???

Thank you for this project. It is great to learn things like this.

1 Like

Hello @krodriguez_fer,

The advanced setting is recommended for both cases - wings and blended winglet.
And YES! Please create the feature refinement for the blended winglet case as well.

Both of these help in obtaining a convergent solution!

Regards,
Sam

1 Like

Hello everybody,
the mesh generation for “aircraft blended wing” was stopped due to:
"The tesselated surface is not closed. There could be a problem with the
Trying to proceed anyway. "

Can anybody help me please to solve this problem?

PS: Mesh generation at first geometry worked fine

Hello @hfoester,

This is just a warning during the snappyHexMesh generation. Your mesh will be generated in spite of this warning, so please continue with creating the mesh and let us know if you encounter an error which hinders from getting a successful mesh. Meanwhile we’ll look into this issue to avoid such warning which might be misleading.

Sam

Hi, I have a problem with the meshing with the wing with winglet. It does not let me select the faces sets, in other words, I select the wing then save and then it disappears like I have not selected it. So I have a problem with the refinement. How can I do? “A mesh refinement without topological entities was found. This refinement will be ignored. Please check the mesh refinements.”

Hi, I have the same problem.

Hi @sjesu_rajendra ,
I receive an error message and the status in the solver log is also “Error”. This means the mesh generation has not finished, even though the software “try to proceed anyway”.

Hello @Dieginho @sebastian_milu,

Do you still encounter the issue? I just checked with a couple of projects, and I don’t encounter this problem.
Could you please check again and tell me? If issues still persists kindly send me from which OS and browser you are trying to use SimScale. I can check and get back to you.

Sam

Hi sjesu_rajendra,
I tried to run the mesh operation again and it worked just fine. Thank you.

I’m Still having the same problem, but just with the wing with winglet. In addition, I cannot finish the simulation, it says “Maximum execution time exceeded.”.

@Dieginho Thanks for the reply. With regard to the simulation run - increase the Maximum runtime setting under Simulation control. I believe the values suggested in the tutorial should be sufficient for the run.

@Dieginho and @hfoester With regard to the mesh - there is some issue with the mesher and our Product Engineers are looking into it now. I will let you know when the issue is resolved. Please try mesh generation after that.

Regards,
Sam

@sjesu_rajendra I have restarted the mesh generation and now (after 3 attempts) it was finished successfully. Thank you

@hfoester, Exactly the issue! Getting a successful mesh is non-deterministic, though it is the same settings. We are looking into it.