External Aerodynamics Setup

Hello! I am currently trying to conduct up an external aerodynamics simulation to find the drag coefficient of a hand model and I have finding troubles setting it up, especially with creating a domain and mesh. Thank you and any help related to my simulation would be highly appreciated!

Hi @sungjoo_lim: Without any reference to you project it is difficult, if not impossible, to answer your question.

Take care,

Retsam

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Hello @Retsam, thank you for your response. Currently, my project is public I would appreciate it if you could take a look at it. What I want to do is create a simulation in which water can flow towards my hand model and analyze it.

You have to post your link here @sungjoo_lim! Make it as easy as possible for the community to help you out :wink:

Cheers!

Jousef

https://www.simscale.com/projects/sungjoo_lim/hand-_0_degree_5/

Thanks for letting me know! :wink:

Hi @sungjoo_lim: I suggest you remove sheet3-5 from your geometry, leaving only solid10.

With new geometry, you will be able to create external CFD simulation, adding a BMB (kind of simulation tunnel) and filling it with water.

Please define BC for side walls as ‘slip walls’.

Use ‘Results control’ > Surface data section to measure forces in front / back of the hand.

When running simulation, please use ‘Potential foam initialisation’ in ‘Advanced concepts > Simulation control’ section.

Take care,

Retsam

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@Retsam
Thank you for your detailed response.
Is there a way to remove the sheets on Simscale or do I have to delete it on the software in which I created the model?

@sungjoo_lim: Please remove those faces “sheets3-5” in your designing software. Later on, you would need to make more sophisticated updates to your hand geometry (like adding fillet) and you have to do it in your CAD software.

Retsam

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@Retsam
Is there a specific instruction video or tutorial I can follow as to how to set up the external cfd simulation? I am having a hard time visualizing it.

@Retsam
I have been able to remove the sheets and only have the solid left now :grinning:

Imagine an object (hand) placed into an aquarium (top will be closed as well). Water in aquarium is your simulation domain. In SimScale, while setting external CFD, you define BMB (this is the aquarium) giving appropriate X Y Z dimensions (6 - 20 times bigger than your geometry).

X would be the flow direction,
Y would be the left / right sides of the BMB
Z would be the vertical dimension of BMB.

That should help to figure out your external CFD setup.

Take care,

Retsam

Hi @sungjoo_lim

I’m a fan of external aerodynamics applied to racecars. What I did to learn how to set up an external aerodynamics simulation was that I watched all the FSAE webinars and workshops (basics and advanced) and read the documentation in Simscale web for easier geometries.

Here the links :

The 1st video I watched for external aerodynamics using Simscale
https://www.simscale.com/docs/tutorials/incompressible-turbulent-airflow-around-a-spoiler/

I recommend the tutorial 2, which is a Full Car FSAE Aerodynamics
https://www.simscale.com/forum/c/workshops-webinars/formula-student-sae-workshop-2017

This is the video I watched to learn how to use a 3rd party post-processing software

Let me know if they have helped you in your question :wink:

Best regards,

Jaime

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@jaimegm16
Hey Jaime! Thank you for your links.
I have been able to follow to first tutorial pretty well until the mesh generating part when the mesh would not be created for the ‘domains’ or ‘boxes’ and only for my model so I am unable to proceed to the next step.

Here are the links for my two tries:
https://www.simscale.com/projects/sungjoo_lim/hand-_0_degree_7/
https://www.simscale.com/projects/sungjoo_lim/hand-0_degree-official-/

Hi sungjoo,

If you are simulating external aerodynamics your material point should be outside the geometry but within the domain.
Try to move the material point on the coord Y=0.1 for example.
Whenever you perform an external aero simulation, your material point should be outside the geometry but within the Background Mesh, in your case, it is inside. Check my answer here, it can be helpful:

@jaimegm16
Hey Jaime! Thanks for the help, I was able to get the mesh done. However, after selecting the material, an option to select the volume doesn’t appear and instead, only an option for the solid appears so I was wondering how to move on from here.

https://www.simscale.com/projects/sungjoo_lim/hand-0_degree-3rd_try-/

This should be the link:

https://www.simscale.com/workbench/?pid=5410271273349632392&mi=spec%3A1af301b8-707c-49fc-93fd-8e1f160537b1%2Cservice%3ASIMULATION%2Cstrategy%3A6&ps=analysis%2FIncompressible--oneOf%2Fmaterials%2Ffluids%2F0

Some pictures of how it looks

30%20PM

You need to select the Mesh as Domain, afterwards the bounding volume should be created.

@jaimegm16
ohh ok, I will try that out! Thank you so much :grinning:

Hello @jaimegm16,

Thanks to you, I did get to set up a simulation using your first link but I was wondering if there was a way to find the drag coefficient of my hand model.

Here’s the link to my project:
https://www.simscale.com/workbench/?pid=5410271273349632392

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