[highpressure]

Hi everyone,


I'm struggling to achieve a smooth cylinder using snappyHexMesh. I've also tried using surfaceFeatureExtract, but I haven't had any success. I’m unsure how to properly mesh the cylinder to get 90° edges and perfect surfaces with snappyHexMesh.


I've attached a screenshot of the cylinder and the case file for reference.


Any help would be greatly appreciated.


Thank you in advance!

[Alczem]

Hey,


For your snap controls, try this:

    nSmoothPatch    2;
    tolerance       2;
    nSolveIter      4;
    nRelaxIter      5;
    nFeatureSnapIter 1;
    implicitFeatureSnap false;
    explicitFeatureSnap true;
    multiRegionFeatureSnap false;

You could also try to use the implicitFeatureSnap but you would need to add resolveFeatureAngle to your castellatedControls.

[highpressure]

Hello Alczem,

Thank you for your response.

Unfortunately, I've tried both of your suggestions, but neither of them seems to be working.

[highpressure]

I've also tried using the surfaceCheck command in OpenFOAM, and the log file indicates that the cylinder is not closed (see log file below). Could this be the problem?

/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2312                                  |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : _e651d635-20240208 OPENFOAM=2312 patch=240220 version=2312
Arch   : "LSB;label=32;scalar=64"
Exec   : surfaceCheck rotating.stl
Date   : May 31 2024
Time   : 16:06:21
Host   : Vostro-3420
PID    : 16667
I/O    : uncollated
Case   : /home/ilyes/OpenFOAM/ilyes-2312/run/Case_file_3D_AMI_updated/constant/triSurface
nProcs : 1
trapFpe: Floating point exception trapping enabled (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 5, maxFileModificationPolls 20)
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Reading surface from "rotating.stl" ...

Statistics:
Triangles    : 180 in 1 region(s)
Vertices     : 184
Bounding Box : (-1 -1.5 -1) (1 1.5 1)

Region Size
------ ----
patch0 180


Surface has no illegal triangles.

Triangle quality (equilateral=1, collapsed=0):
    0 .. 0.05  : 0.266667
    0.05 .. 0.1  : 0.622222
    0.1 .. 0.15  : 0.0777778
    0.15 .. 0.2  : 0.0166667
    0.2 .. 0.25  : 0.0166667
    0.25 .. 0.3  : 0
    0.3 .. 0.35  : 0
    0.35 .. 0.4  : 0
    0.4 .. 0.45  : 0
    0.45 .. 0.5  : 0
    0.5 .. 0.55  : 0
    0.55 .. 0.6  : 0
    0.6 .. 0.65  : 0
    0.65 .. 0.7  : 0
    0.7 .. 0.75  : 0
    0.75 .. 0.8  : 0
    0.8 .. 0.85  : 0
    0.85 .. 0.9  : 0
    0.9 .. 0.95  : 0
    0.95 .. 1  : 0

    min 0.000976297 for triangle 130
    max 0.234722 for triangle 177

Edges:
    min 0.136485 for edge 188 points (0.775711 -1.5 0.631088)(0.682553 -1.5 0.730836)
    max 3.0031 for edge 9 points (0.775711 1.5 0.631088)(0.854419 -1.5 0.519584)

Checking for points less than 1e-6 of bounding box ((2 3 2) metre) apart.
Found 0 nearby points.

Surface is not closed since not all edges (362) connected to two faces:
    connected to one face : 184
    connected to >2 faces : 0
Conflicting face labels:184

Number of unconnected parts : 3
Splitting surface into parts ...

Wrote zoning to "./rotating.vtp"

writing part 0 size 92 to "./rotating_0.obj"
writing part 1 size 44 to "./rotating_1.obj"
writing part 2 size 44 to "./rotating_2.obj"

Number of zones (connected area with consistent normal) : 3
More than one normal orientation.
Wrote zoning to "./rotating.vtp"

writing part 0 size 92 to "./rotating_normal_0.obj"
writing part 1 size 44 to "./rotating_normal_1.obj"
writing part 2 size 44 to "./rotating_normal_2.obj"


End

[highpressure]

Any help ?

[Yann]

Hello,

Yes, the surface not being closed may be the problem.
(this reminds me of this: snappyHexMesh - 90° edges problem)

You can use surfaceHookup and surfacePointMerge utilities to fix your stl file: Surface Check and Repair Utilities - Need Explanation

[Alczem]

Hey!


Too bad, but you are right, it probably comes from the STLs.


Since the issue lies with the rotating.stl file, you could try to replace it by a searchableCylinder. That way, you don't have to care about the STL quality. SnappyHexMesh will see no difference.

[highpressure]

Originally Posted by Yann

Hello,

Yes, the surface not being closed may be the problem.
(this reminds me of this: snappyHexMesh - 90° edges problem)

You can use surfaceHookup and surfacePointMerge utilities to fix your stl file: Surface Check and Repair Utilities - Need Explanation

Bonjour Yann,

Thank you for your answer !

[highpressure]

Originally Posted by Alczem

Hey!


Too bad, but you are right, it probably comes from the STLs.


Since the issue lies with the rotating.stl file, you could try to replace it by a searchableCylinder. That way, you don't have to care about the STL quality. SnappyHexMesh will see no difference.

Hello Alczem;

It finally works ! Thanks a lot for your help