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Termination of T-rex layers against adjacent domain

JH202408202239

Hello everyone,

I am making a mesh for an internal flow around a cone. I use the T-rex algorithm to create inflation layers. See the left image below. On the left hand side you can see one of the domains that form the boundaries of the block, which has the boundary type 'match'. In order to mesh the adjacent block nicely, I had to set the number of T-rex layers lower than in this block. As a result, the T-rex algorithm needs to add in 5 additional layers coming off of the 'match' domain (or terminate  layers coming towards the 'match' domain depending on your reference). However, the way in which it does this, creates highly skewed cells (view the image on left below). The top layers are curved upwards creating a much taller cell in the middle of the inflation layer. The behaviour I would expect is in the image on the right, where the additional layers are neatly stacked on the others. This still creates skewed cells, but less so.

Can you explain why this behaviour occurs and how I might obtain something that resembles the right picture? Thank you very much!

  • 0 in reply to Claudio M Pita

    Hi Caudio,

    Thank you for your elaborate answer and continued help. It would be great if we can turn this into a regular support ticket.

    In the meantime I tried your options, to no avail:

    Options 1) and 2) create highly skewed cells in certain areas through the automatic processes which is very finicky to get rid with a lot of trial and error. Option 3) gives the result as shown in the image below. As you can see I split the block (and thus the domain) at the end of y the T-rex layers of the left block. The green domain is set to 'Match' and the yellow domain is turned off. Now, however, the T-rex algorithm stops itself 1 layer shy of the top of the green domain for some reason, which again creates highly skewed cells as it tries to fill the volume in that missing cell (you can see where the T-rex stops where the blue-coloured prisms turn into the red-coloured tetras). This method seems to have the potential to fix the issue, if the T-rex layer is able to continue all the way up to the top of the green domain. 

  • 0 in reply to JH202408202239

    Hi, 

    Thank you very much for giving these options a try and reporting back.

    If you would like to try a slight variation of Option 3, perhaps you could use the split by distance option to split the block (and the interface domain) a bit above the last T-Rex layer seen in the green domain to see if this provides better results. 

    If the above doesn't work, we would need to turn this into a regular support ticket so you can please share the Fidelity Pointwise file and we can investigate better options to work around the problem and ultimately to resolve it. 

    A few things to note:

    • Unfortunately, I cannot create a support ticket in your behalf because I don't have any of your information. I am not sure if you are part of an organization or a university. If the former, you should be able to create an account in COS and log a support ticket. If the latter, you will likely need to work through your advisor to log a ticket (unless your are added as a university user who can log support ticket by your advisor). 
    • Here are a couple of videos showing the process to create a COS account and log a ticket:
    • We were able to reproduce the problem in-house with a made up case and a Software Performance Report has been created to further investigate the issue: PW-25587.

    I hope this information is useful. Please let me know how it goes. 

    Best regards,

  • 0 in reply to Claudio M Pita

    Hi Claudio,

    I tried your suggestion, and increased the distance of the split so that it is one cell above the end of the T-rex layers all around the cone. You can see the result in the image below. This method improves the result: there are now only 47 cells with a skewness above 0.9. But there are still cells created in a manner that I think can be improved to reduce the maximum skewness (the maximum now was 0.96). 

    As for the ticket: I am not able to create a ticket via our COS account, but our license partner at Tecplot can. The geometry is confidential, so I would not be able to send this. Nevertheless, I think this problem is not heavily dependent on the geometry (seeing that you managed to reproduce it). I would like to keep up to date with any progress regarding the software performance report PW-25587. If you think you can assist me in another way via the ticket, that would be great of course.

  • 0 in reply to JH202408202239

    Hi, 

    Thank you very much for the update. 

    Here my comments:

    • Unfortunately, this particular issue seems to be related to the geometry to some extent considering that, even though we were able to reproduce the issue, in our sample case the recommended block split approach resolved the problem and provided a satisfactory grid. 
    • That being said, if you have a few cells that need additional improvement, I would recommend:
    • Last but not last, in order to keep you up-to-date with the progress of PW-25587, we would need a support ticket in COS with your contact information so our systems can send an email when the issue is resolved. If this isn't possible, I would recommend to check the Release Notes available with each release to see if the issue in question has been resolved. 

    Thank you very much for your time and help!

    Best regards,

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