[stopherkri]

Hello guys,

I was wondering if it's possible to use only the addLayers part of snappyHexMesh to a mesh created with blockMesh (so I have no stls in the triSurface folder).

Appreciate your help.

[AtoHM]

Uh, not sure, never used it this way. Maybe someone else has?

I just want to add: you can use grading in blockMesh to generate clean perfect layers there even for very low y+ which would likely not be possible in sHM.

[GerhardHolzinger]

Should be possible, why don't you just try it?

[stopherkri]

Originally Posted by AtoHM

Uh, not sure, never used it this way. Maybe someone else has?

I just want to add: you can use grading in blockMesh to generate clean perfect layers there even for very low y+ which would likely not be possible in sHM.

I did the grading with blockMesh previously, but I'm modelling steps so the corners are the problem I'm getting big values of y+ in the "riser" part of the step. Maybe I could divide each step in two blocks, but I have more than 10 steps so i'm looking for a workaround.

[stopherkri]

Originally Posted by GerhardHolzinger

Should be possible, why don't you just try it?

Apparently it needs to run castellatedMesh first. So I use surfaceMeshExtract to create and stl of my patch but when running snappyHexMesh the surfaces don't seem to align perfectly, so I end up with two surfaces.

[Yann]

Originally Posted by stopherkri

Apparently it needs to run castellatedMesh first. So I use surfaceMeshExtract to create and stl of my patch but when running snappyHexMesh the surfaces don't seem to align perfectly, so I end up with two surfaces.

At the beginning of snappyHexMeshDict, you can deactivate the castellated and snap steps to only run the addLayers step:

// Which of the steps to run
castellatedMesh false;
snap            false;
addLayers       true;

This should allow you to add layers on your mesh created with blockMesh.

[stopherkri]

Originally Posted by Yann

At the beginning of snappyHexMeshDict, you can deactivate the castellated and snap steps to only run the addLayers step:

// Which of the steps to run
castellatedMesh false;
snap            false;
addLayers       true;

This should allow you to add layers on your mesh created with blockMesh.

I've tried that, but It seems like it is requiered to run castellatedMesh previously which I've done by creating a stl surface from my blockMeshDict. However, I have not been succesful since my mesh doesn't intersect perfectly with this surface.

[AtoHM]

Technically I agree, it should work, but I was vague in my first comment, because I am not totally sure how. We can deactivate the other steps, but I am not sure how to adress the entities from blockMesh.
In the template sHMDict I am always using, we have a comment saying

// Per final patch (so not geometry!) the layer information

layers
{
 ...
}

I guess it comes from some annotated dict in an offical repo. Normally, when using STLs we add here the region names of the STL with the respective number of layers. What do we add for blockMesh? According to the comment, we need to create proper patches there and then we can adress them?

[Yann]

Originally Posted by stopherkri

I've tried that, but It seems like it is requiered to run castellatedMesh previously which I've done by creating a stl surface from my blockMeshDict.

Which version of OpenFOAM are you using ?

Can you give details of what you tried and why you say it requires to run castellatedMesh previously? (for instance, sharing your blockMeshDict, snappyHexMeshDict and logs, error message...)

Originally Posted by AtoHM

Technically I agree, it should work, but I was vague in my first comment, because I am not totally sure how. We can deactivate the other steps, but I am not sure how to adress the entities from blockMesh.
In the template sHMDict I am always using, we have a comment saying

// Per final patch (so not geometry!) the layer information

layers
{
 ...
}

I guess it comes from some annotated dict in an offical repo. Normally, when using STLs we add here the region names of the STL with the respective number of layers. What do we add for blockMesh? According to the comment, we need to create proper patches there and then we can adress them?

You can add layers on the blockMesh patches, you don't need STL for this.
Check the motorBike case for example, where layers are added on the lowerWall, which is a patch created in blockMesh and not from the STL/OBJ surface.
Actually you can easily check this by removing all mentions to the motorbike in the motorbile tutorial and only add layers on some of the blockMesh patches.

[stopherkri]

Originally Posted by Yann

Which version of OpenFOAM are you using ?

Can you give details of what you tried and why you say it requires to run castellatedMesh previously? (for instance, sharing your blockMeshDict, snappyHexMeshDict and logs, error message...)





You can add layers on the blockMesh patches, you don't need STL for this.
Check the motorBike case for example, where layers are added on the lowerWall, which is a patch created in blockMesh and not from the STL/OBJ surface.
Actually you can easily check this by removing all mentions to the motorbike in the motorbile tutorial and only add layers on some of the blockMesh patches.

You were right sir. It only needs a stl (it doesn't even matter if its related to the mesh or not) to run which is not even use in the addLayers part of snappyHexMesh.

Thanks to everyone.

[Yann]

Glad to know it works!

Feel free to post your snappyHexMeshDict here, because you should not have to provide any STL file.
(just remove what you may have left defined in the geometry {}, features{}, refinementSurfaces{} and refinementRegions {} sections)

[AtoHM]

... and blockMeshDict too (or a reduced version showing how it works in principle) for other users coming here with the same question.