scFLOW　メッシュ作成について

Hi, Atsuya

Thanks for posting your question.  I'll try to help you with the prism and octree specifications.

Actually, there was a thread on here last week that should help with your prism settings.  Please look for "How to control the prism layer thickness in scFLOW?" in the thread list.  And here is a direct link:

 How to control the prism layer thickness in scFLOW? 

The image in my first reply there shows the dialog where you can set first prism layer thickness; change ratio; and number of layers.  You'll need to have a registered surface for the human body to [<< Apply] the prism settings to it.  You probably have that already, but if not, you can use the default surface for that part, which will have "Part Surface (@" at the start of the surface name.

Also, here are links to a couple of recent SimCompanion [Knowledge] articles on the subject of prism layer insertion:

https://simcompanion.hexagon.com/customers/s/article/How-to-control-prism-layer-thickness-in-scFLOW

https://simcompanion.hexagon.com/customers/s/article/How-to-determine-the-first-prism-layer-height-to-achieve-a-specific-y-value

There's an Excel sheet prism layer calculator included in the second of these articles.  One of the things it gives you is an [Estimated local octant size], so you could use that as the octant size of the human body surface.  The article explains how this octant size relates to the selected prism size.

Regarding octree creation (and mesh generation) in general, please refer to these scFLOW exercises:

- [Training 2] in the Operation manual; this includes octree refinement for external flow over a glider, though I don't think you'll need to worry about a wake region for flow around your human body.

- [exA29-1] in the Exercise manual is an application of the scFLOW JOS model for a human standing in an air-conditioned room.  So, that will maybe give you some ideas on octant sizes to use in your model.  I would go a bit finer than the exercise does, though.  The exercises tend to use quite coarse meshes so that the user does not have to wait very long for the simulation to complete.

Since you are new to Cradle CFD, I should also mention that the user manuals can be opened from the blue book icon in the top row of the scFLOW Kicker.  Also, if you don't already have the files for the exercises I've mentioned above, please download the Zip-file that contains all the scFLOW sample data.  You can find it online, at the same location where you downloaded the Cradle CFD installer.

If you're in doubt about whether your mesh is fine enough, you can try a mesh sensitivity study, where you compare the results from a few different meshes (say, 3, for "coarse", "medium", and "fine" meshes).  Basically, the mesh should be fine enough so that further refinement of it will not significantly affect the key results from your simulation.  So, your coarse mesh could be based on exA29-1, then use smaller octant (and prism) settings to some up with medium and fine meshes.  And when you use smaller octants on the human body, also reduce your other specified octant sizes by the same ratio.

I hope this is enough information to answer your question.  Please let me know if you have any follow-up question.

Regards,

- David

Hi, Atsuya

Thanks for posting your question.  I'll try to help you with the prism and octree specifications.

Actually, there was a thread on here last week that should help with your prism settings.  Please look for "How to control the prism layer thickness in scFLOW?" in the thread list.  And here is a direct link:

 How to control the prism layer thickness in scFLOW? 

The image in my first reply there shows the dialog where you can set first prism layer thickness; change ratio; and number of layers.  You'll need to have a registered surface for the human body to [<< Apply] the prism settings to it.  You probably have that already, but if not, you can use the default surface for that part, which will have "Part Surface (@" at the start of the surface name.

Also, here are links to a couple of recent SimCompanion [Knowledge] articles on the subject of prism layer insertion:

https://simcompanion.hexagon.com/customers/s/article/How-to-control-prism-layer-thickness-in-scFLOW

https://simcompanion.hexagon.com/customers/s/article/How-to-determine-the-first-prism-layer-height-to-achieve-a-specific-y-value

There's an Excel sheet prism layer calculator included in the second of these articles.  One of the things it gives you is an [Estimated local octant size], so you could use that as the octant size of the human body surface.  The article explains how this octant size relates to the selected prism size.

Regarding octree creation (and mesh generation) in general, please refer to these scFLOW exercises:

- [Training 2] in the Operation manual; this includes octree refinement for external flow over a glider, though I don't think you'll need to worry about a wake region for flow around your human body.

- [exA29-1] in the Exercise manual is an application of the scFLOW JOS model for a human standing in an air-conditioned room.  So, that will maybe give you some ideas on octant sizes to use in your model.  I would go a bit finer than the exercise does, though.  The exercises tend to use quite coarse meshes so that the user does not have to wait very long for the simulation to complete.

Since you are new to Cradle CFD, I should also mention that the user manuals can be opened from the blue book icon in the top row of the scFLOW Kicker.  Also, if you don't already have the files for the exercises I've mentioned above, please download the Zip-file that contains all the scFLOW sample data.  You can find it online, at the same location where you downloaded the Cradle CFD installer.

If you're in doubt about whether your mesh is fine enough, you can try a mesh sensitivity study, where you compare the results from a few different meshes (say, 3, for "coarse", "medium", and "fine" meshes).  Basically, the mesh should be fine enough so that further refinement of it will not significantly affect the key results from your simulation.  So, your coarse mesh could be based on exA29-1, then use smaller octant (and prism) settings to some up with medium and fine meshes.  And when you use smaller octants on the human body, also reduce your other specified octant sizes by the same ratio.

I hope this is enough information to answer your question.  Please let me know if you have any follow-up question.

Regards,

- David