TELEMAC-MASCARET Forum: Element size less than 1m (1/1)

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TOPIC: Element size less than 1m

Element size less than 1m 11 years 10 months ago #6900

simon.nolin

Hi,

To simulate flow through a narrow passage, I need to work with small elements : less than 1 m. Is there some limitations in Blue Kenue when working with small meshes?? If so, what can be done to avoid meshing problems? Whit small meshes, I often get "flat triangles" issues resulting in the error "Determinant negatif" in Telemac-2D. Can we verify the mesh generated with BK before running Telemac?

Thanks,
Simon

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Element size less than 1m 11 years 10 months ago #6901

c.coulet OFFLINE Moderator Posts: 3722 Thank you received: 1031	Hi With small mesh, you should take care to the accuracy! By default, selafin file use simple precision for coordinates and this could create problems due to the rounding if your coordinate system use very large numbers. Since the latest version, a new format has been added (named SELAFIND) which manage the coordinates in double precision Try to look on this direction Regards
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Element size less than 1m 11 years 10 months ago #6904

Serrer OFFLINE Moderator Posts: 720 Thank you received: 304	Hi Simon, This has been discussed in a previous post You need to shift your source data to resolve the issue of truncation of coordinates. See post #5626 in the topic "Flat triangle in mesh generated with BlueKenue" for more info. www.opentelemac.org/index.php/kunena/blu...ekenue?start=10#5626 Cheers... Martin
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Element size less than 1m 11 years 10 months ago #6906

simon.nolin	Hi Martin, Thanks for your answer. I am indeed using a projection with large coordinates values (MTM). As suggested, I'll try to shift everything and see if its works. Cheers, Simon
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Element size less than 1m 11 years 10 months ago #6907

Fauret OFFLINE Junior Boarder Posts: 44 Thank you received: 12	Hi Simon When I worked with a translated grid, I found a very useful key word in the cas file: ORIGIN COORDINATES. You then have access to the 2 translations in the fortran through the variable I_ORIG, J_ORIG. I used it when I was dealing with other files still in the original UTM system. Thierry
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