[GiDlist] Re: GiDlist digest, Vol 1 #414 - 1 msg
Posted: Tue Jul 01, 2003 12:27 pm
Thank you very much,
I do appreciate your repply and your effort.
I am working with GID in boundary elements methods (BEM).
This definition of gauss points ( a = 1/6, b = 2/3, c = 5/12, d = 1/6)
is very common in BEM, when using triangular discontinuous elements.
I believe that anyone working with BEM will really appreciate this
feature of GID.
best regards,
Andres
gidlist-request at gatxan.cimne.upc.es wrote:
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______________________________________________________________________
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Today's Topics:
1. Re: inaccurate postprocessing with given Gauss points (Miguel A. de Riera Pasenau)
--__--__--
Message: 1
Date: Tue, 01 Jul 2003 10:50:54 +0200
From: "Miguel A. de Riera Pasenau" miguel at cimne.upc.es
Organization: CIMNE ( UPC)
To: gidlist at gatxan.cimne.upc.es
Subject: Re: [GiDlist] inaccurate postprocessing with given Gauss points
Reply-To: gidlist at gid.cimne.upc.es
Yes, there was a problem with inverting a matrix when zeros appeared
on the diagonal. With 0.16667 there was no problem, but with 0.1666666666666666667.
i think i will prepare a new beta this week with this problem solved.
miguel
Andres Peratta wrote:
When postprocessing scalar results with "given" gauss points
I found out that the visualization becomes quite inaccurate.
For example Contour_fill and Contour_lines options, dont' work properly.
It seems that the defined coordinates of the gauss points should not have
more than 5 decimal figures,
otherwise the given coordinates in the .res file are not read properly
by GID.
To see what is going on, you can try the following example in which
a scalar field
u(x,y) = x
is visualized in a single unitary triangular element with 6 gauss points
located at the following coordinates :
a = 1/6, b = 2/3, c = 5/12, d = 1/6
( a, a) ( b, a) ( a, b) ( c, d) ( c, c) ( d, c)
( see the attached .res file in which I used different precisions to
represent the fractional
numbers 1/6, 2/3 and 5/12 , and see what happens when contour_lines
or contour_fill options are selected )
The main problem is that if I want to increase the precision of the
given coordinates,
beyond 5 figures the result is completely unpredictable,
and if I keep 5 or less figures, the visualization does not reflect the
real scalar field.
Is there any solution ?
Has anyone faced this problem before ?
Thanks for your help.
best regards,
Andres
--
Andres B. Peratta
Wessex Institute of Technology
Email: andres at wessex.ac.uk
Tel: +44 (0)238 029 3223
Fax: +44 (0)238 029 2853
Ashurst Lodge
Ashurst
Southampton (SO40-7AA)
UK
------------------------------------------------------------------------------------------------------------------------------------
Gid Post Results File 1.0
GaussPoints "gauss1" Elemtype Triangle
Number Of Gauss Points: 6
Natural Coordinates: Given
0.16667 0.16667
0.66667 0.16667
0.16667 0.66667
0.41667 0.16667
0.41667 0.41667
0.16667 0.41667
End GaussPoints
GaussPoints "gauss2" Elemtype Triangle
Number Of Gauss Points: 6
Natural Coordinates: Given
0.166666666667 0.166666666667
0.666666666667 0.166666666667
0.166666666667 0.666666666667
0.416666666667 0.166666666667
0.416666666667 0.416666666667
0.166666666667 0.416666666667
End GaussPoints
GaussPoints "gauss3" Elemtype Triangle
Number Of Gauss Points: 6
Natural Coordinates: Internal
End GaussPoints
Result "uf" "Convergency" 2.0000E+00 scalar OnGaussPoints "gauss1"
Values
1 0.16667
0.16667
0.66667
0.16667
0.41667
0.41667
End Values
Result "uf" "Convergency" 2.0000E+00 scalar OnGaussPoints "gauss2"
Values
1 0.16667
0.16667
0.66667
0.16667
0.41667
0.41667
End Values
Result "uf" "Convergency" 2.0000E+00 scalar OnGaussPoints "gauss3"
Values
1 0.16667
0.16667
0.66667
0.16667
0.41667
0.41667
End Values
------------------------------------------------------------------------------------------------------------------------------------
Name: testgp.geo
testgp.geo Type: unspecified type (application/octet-stream)
Encoding: base64
Name: testgp.msh
testgp.msh Type: model/mesh
Encoding: quoted-printable
Name: testgp.flavia.msh
testgp.flavia.msh Type: model/mesh
Encoding: 7bit
--
Andres B. Peratta
PhD Student
Wessex Institute of Technology
Email: andres at wessex.ac.uk
Tel: +44 (0)238 029 3223
Fax: +44 (0)238 029 2853
Ashurst Lodge
Ashurst
Southampton (SO40-7AA)
UK
I do appreciate your repply and your effort.
I am working with GID in boundary elements methods (BEM).
This definition of gauss points ( a = 1/6, b = 2/3, c = 5/12, d = 1/6)
is very common in BEM, when using triangular discontinuous elements.
I believe that anyone working with BEM will really appreciate this
feature of GID.
best regards,
Andres
gidlist-request at gatxan.cimne.upc.es wrote:
Send GiDlist mailing list submissions to
gidlist at gid.cimne.upc.es
To subscribe or unsubscribe via the World Wide Web, visit
http://gid.cimne.upc.es/mailman/listinfo/gidlist
or, via email, send a message with subject or body 'help' to
gidlist-request at gid.cimne.upc.es
You can reach the person managing the list at
gidlist-admin at gid.cimne.upc.es
When replying, please edit your Subject line so it is more specific
than "Re: Contents of GiDlist digest..."
______________________________________________________________________
Los envios para la lista de correo GiDlist han de enviarse a
gidlist at gid.cimne.upc.es
Para subscribirse o desapuntarse via World Wide Web, visite
http://gid.cimne.upc.es/mailman/listinfo/gidlist
o, via email, enviando un mensaje con 'help' en el 'asunto' o 'cuerpo'
a
gidlist-request at gid.cimne.upc.es
Puede contactar con la persona que administra la lista bajo
gidlist-admin at gid.cimne.upc.es
Cuando responda, por favor, edite la linea del 'asunto' para que sea
más especifica que "Re: Contenido resumen de GiDlist ..."
Today's Topics:
1. Re: inaccurate postprocessing with given Gauss points (Miguel A. de Riera Pasenau)
--__--__--
Message: 1
Date: Tue, 01 Jul 2003 10:50:54 +0200
From: "Miguel A. de Riera Pasenau" miguel at cimne.upc.es
Organization: CIMNE ( UPC)
To: gidlist at gatxan.cimne.upc.es
Subject: Re: [GiDlist] inaccurate postprocessing with given Gauss points
Reply-To: gidlist at gid.cimne.upc.es
Yes, there was a problem with inverting a matrix when zeros appeared
on the diagonal. With 0.16667 there was no problem, but with 0.1666666666666666667.
i think i will prepare a new beta this week with this problem solved.
miguel
Andres Peratta wrote:
When postprocessing scalar results with "given" gauss points
I found out that the visualization becomes quite inaccurate.
For example Contour_fill and Contour_lines options, dont' work properly.
It seems that the defined coordinates of the gauss points should not have
more than 5 decimal figures,
otherwise the given coordinates in the .res file are not read properly
by GID.
To see what is going on, you can try the following example in which
a scalar field
u(x,y) = x
is visualized in a single unitary triangular element with 6 gauss points
located at the following coordinates :
a = 1/6, b = 2/3, c = 5/12, d = 1/6
( a, a) ( b, a) ( a, b) ( c, d) ( c, c) ( d, c)
( see the attached .res file in which I used different precisions to
represent the fractional
numbers 1/6, 2/3 and 5/12 , and see what happens when contour_lines
or contour_fill options are selected )
The main problem is that if I want to increase the precision of the
given coordinates,
beyond 5 figures the result is completely unpredictable,
and if I keep 5 or less figures, the visualization does not reflect the
real scalar field.
Is there any solution ?
Has anyone faced this problem before ?
Thanks for your help.
best regards,
Andres
--
Andres B. Peratta
Wessex Institute of Technology
Email: andres at wessex.ac.uk
Tel: +44 (0)238 029 3223
Fax: +44 (0)238 029 2853
Ashurst Lodge
Ashurst
Southampton (SO40-7AA)
UK
------------------------------------------------------------------------------------------------------------------------------------
Gid Post Results File 1.0
GaussPoints "gauss1" Elemtype Triangle
Number Of Gauss Points: 6
Natural Coordinates: Given
0.16667 0.16667
0.66667 0.16667
0.16667 0.66667
0.41667 0.16667
0.41667 0.41667
0.16667 0.41667
End GaussPoints
GaussPoints "gauss2" Elemtype Triangle
Number Of Gauss Points: 6
Natural Coordinates: Given
0.166666666667 0.166666666667
0.666666666667 0.166666666667
0.166666666667 0.666666666667
0.416666666667 0.166666666667
0.416666666667 0.416666666667
0.166666666667 0.416666666667
End GaussPoints
GaussPoints "gauss3" Elemtype Triangle
Number Of Gauss Points: 6
Natural Coordinates: Internal
End GaussPoints
Result "uf" "Convergency" 2.0000E+00 scalar OnGaussPoints "gauss1"
Values
1 0.16667
0.16667
0.66667
0.16667
0.41667
0.41667
End Values
Result "uf" "Convergency" 2.0000E+00 scalar OnGaussPoints "gauss2"
Values
1 0.16667
0.16667
0.66667
0.16667
0.41667
0.41667
End Values
Result "uf" "Convergency" 2.0000E+00 scalar OnGaussPoints "gauss3"
Values
1 0.16667
0.16667
0.66667
0.16667
0.41667
0.41667
End Values
------------------------------------------------------------------------------------------------------------------------------------
Name: testgp.geo
testgp.geo Type: unspecified type (application/octet-stream)
Encoding: base64
Name: testgp.msh
testgp.msh Type: model/mesh
Encoding: quoted-printable
Name: testgp.flavia.msh
testgp.flavia.msh Type: model/mesh
Encoding: 7bit
--
Andres B. Peratta
PhD Student
Wessex Institute of Technology
Email: andres at wessex.ac.uk
Tel: +44 (0)238 029 3223
Fax: +44 (0)238 029 2853
Ashurst Lodge
Ashurst
Southampton (SO40-7AA)
UK