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TOPIC: Negative determinant

Negative determinant 10 years 10 months ago #11650

  • dsc1r12
  • dsc1r12's Avatar
Hi,

I am trying to run a model in Telemac 2D, however I recieve the following error:

CALLING LECLIM
BACK FROM LECLIM
CALLING INBIEF
INBIEF (BIEF): NOT A VECTOR MACHINE (ACCORDING TO YOUR DATA)
CORLAT :NO MODIFICATION OF LATITUDE
GEOELT: ELEMENT 1811 : NEGATIVE DETERMINANT

I thought that as I was getting a negative determinant, if I simplified the geometry this may help, however I still get the same problem.

If I turn off spherical coordinates in the steering file, I do not get this error, however the domain is so large that spherical coordinates are needed.

Can anyone help me with this please?

Cheers

Danny
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Negative determinant 10 years 10 months ago #11655

  • jmhervouet
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Hello,

this is not normal, when SPHERICAL COORDINATES = YES, you just tell that your mesh is given in a Mercator projection, the program will retrieve the latitude from the coordinates in the mesh, to solve the spherical equations. A negative determinant means that an element is not well oriented, i.e. points 1,2 and 3 of the element go around the element clockwise. According to the previous post by Martin Serrer, Blue Kenue gives well oriented elements, so this should not happen. Please note that when you give a mesh with a Mercator projection, you have also keywords : LATITUDE OF ORIGIN POINT and LONGITUDE OF ORIGIN POINT, the projection is supposed to be done around this point, maybe it is your problem.

Regards,

Jean-Michel Hervouet
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Negative determinant 10 years 10 months ago #11664

  • dsc1r12
  • dsc1r12's Avatar
Hi Jean-Michel,

I tried putting in LATITUDE OF ORIGIN POINT and LONGITUDE OF ORIGIN POINT,but the same problem still comes up with a negative determinant.

It is strange because the command window says 'My work is done', however when I try and open the Results.slf file in Blue Kenue, I get an error message saying the following...

While reading header.
ERROR: Unknown or invalid file format.

Cheers

Danny
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Negative determinant 10 years 10 months ago #11671

  • jmhervouet
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Hello,

Well, I do not really know what happens, certainly a misunderstanding somewhere, so please send me the files you run and I'll try to see what the problem is.

Regards,

JMH
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Negative determinant 10 years 10 months ago #11675

  • dsc1r12
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Hi JMH,

Here are the files,

Cheers

Danny
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Negative determinant 10 years 10 months ago #11678

  • jmhervouet
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Geometry file missing, if problem send it directly to This email address is being protected from spambots. You need JavaScript enabled to view it..
Message to all users: please do not send questions to my E-mail...
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Negative determinant 10 years 10 months ago #11679

  • dsc1r12
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Apologies, I forgot teh geometry file, here you go...
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Negative determinant 10 years 10 months ago #11680

  • dsc1r12
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Sorry, there was an issue with the size of the file, I have reduced the mesh so hopefully it should work this time...
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Negative determinant 10 years 10 months ago #11681

  • jmhervouet
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If you reduce the mesh, will there still be the same problem ? and the boundary conditions file must correspond to this new mesh...

JMH
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Negative determinant 10 years 10 months ago #11682

  • lsb1@soton.ac.uk
  • lsb1@soton.ac.uk's Avatar
Shifting the y-coordinates of the mesh by -4.3e6 m and setting LATITUDE OF ORIGIN POINT = 36.0305 seems to work. I guess there is a precision issue somewhere? I note this in GEOELT:
         IF(DET.LT.1.D-20)
           ...
99         FORMAT(1X,'GEOELT: ELEMENT ',1I6,' : NEGATIVE DETERMINANT')
           STOP
         ENDIF

I wonder if it would help to reduce the threshold?
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