[snappyHexMesh] Understanding the Propeller tutorial

mahtin360 · April 3, 2014, 12:13

Hello,

I've recently started with OpenFOAM (2.3.0) and want to simulate rotating propellers.

I'm looking at the propeller tutorial and trying to understand how AMI patches are generated. I've tried to use SHM to do my own geometry but when I look at the two AMI patches, they look quite different. As far as I understand in the propeller tutorial they both come from the innerCylinderSmall geometry and the AMI is created using topoSet?

Could someone explain why if they can be different when I look at my own cylinders in ParaView, aren't the same mesh refinements applied in SHM? Do I have to work with the topoSet and createPatch dicts to work around this or is this a matter of mesh refinment?

thank you for any hints on this
Martin

AMI.jpg

AMI1.jpg

pbachant · April 5, 2014, 20:36

Are you naming them the same way? Make sure you have the explicit feature edge section of the snappyHexMeshDict set correctly, and that your surfaceFeatureExtractDict is also correct. Beyond that, I've had luck increasing the number of feature snap iterations from 10 to around 50.

mahtin360 · April 7, 2014, 07:01

Hi, thanks for your hints.
I've got it working with a new stl file and not specifying explicit feature edges at the moment. I will try increasing the iterations if I run into similar problems while refining further.
Yes, I'm following the tutorial. They both come from my innerCylinderSmall.stl file. I'm actually wondering where exactly the innerCylinderSmall and innerCylinderSmall_slave come from i.e at what stage these are generated and how?

pbachant · April 7, 2014, 16:30

Quote:

Originally Posted by mahtin360

Hi, thanks for your hints.
I've got it working with a new stl file and not specifying explicit feature edges at the moment. I will try increasing the iterations if I run into similar problems while refining further.
Yes, I'm following the tutorial. They both come from my innerCylinderSmall.stl file. I'm actually wondering where exactly the innerCylinderSmall and innerCylinderSmall_slave come from i.e at what stage these are generated and how?

I believe these are generated with snappyHexMesh, and then AMI1 and AMI2 are created with createPatch.

mahtin360 · April 9, 2014, 11:47

Yes, I was just wondering if anyone has some more information as to when these are generated as it seemed the two patches came out differently in my case. I'm just wondering why for one of the AMIs the edges are different to the other one.

April 3, 2014, 12:13	Understanding the Propeller tutorial	#1
mahtin360 New Member Martin Join Date: Oct 2013 Location: Newcastle Posts: 21 Rep Power: 13	Hello, I've recently started with OpenFOAM (2.3.0) and want to simulate rotating propellers. I'm looking at the propeller tutorial and trying to understand how AMI patches are generated. I've tried to use SHM to do my own geometry but when I look at the two AMI patches, they look quite different. As far as I understand in the propeller tutorial they both come from the innerCylinderSmall geometry and the AMI is created using topoSet? Could someone explain why if they can be different when I look at my own cylinders in ParaView, aren't the same mesh refinements applied in SHM? Do I have to work with the topoSet and createPatch dicts to work around this or is this a matter of mesh refinment? thank you for any hints on this Martin AMI.jpg AMI1.jpg

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April 5, 2014, 20:36		#2
pbachant Senior Member Pete Bachant Join Date: Jun 2012 Location: Boston, MA Posts: 173 Rep Power: 14	Are you naming them the same way? Make sure you have the explicit feature edge section of the snappyHexMeshDict set correctly, and that your surfaceFeatureExtractDict is also correct. Beyond that, I've had luck increasing the number of feature snap iterations from 10 to around 50.

April 7, 2014, 07:01		#3
mahtin360 New Member Martin Join Date: Oct 2013 Location: Newcastle Posts: 21 Rep Power: 13	Hi, thanks for your hints. I've got it working with a new stl file and not specifying explicit feature edges at the moment. I will try increasing the iterations if I run into similar problems while refining further. Yes, I'm following the tutorial. They both come from my innerCylinderSmall.stl file. I'm actually wondering where exactly the innerCylinderSmall and innerCylinderSmall_slave come from i.e at what stage these are generated and how?

April 9, 2014, 11:47		#5
mahtin360 New Member Martin Join Date: Oct 2013 Location: Newcastle Posts: 21 Rep Power: 13	Yes, I was just wondering if anyone has some more information as to when these are generated as it seemed the two patches came out differently in my case. I'm just wondering why for one of the AMIs the edges are different to the other one.