[GiDlist] Mesh problem

[Enrique Escolano]

Dear Sir.

The quadratic nodes are not located at the midpoint element edge, are located over the source curved line, and it this curve
is not uniformly parameterized, then the point with mid parameter (0.5 ) must be far the midpoint curve.

You can use some trick to move this quadratic nodes to the mid-egde,
for example, I attach a sample problemtype to move this nodes automatically after generate the mesh, using some Tcl procedure.

This sample only works for 8 noded quadrilaterals.
Unzip this file inside the GiD problemtype directory, then restart GiD and load it with
Data-Problemtype-CenterQuadraticNodes

This is the Tcl included code:

proc InitGIDProject { dir } {
#procedure automatically called by GiD
}

proc EndGIDProject {} {
#procedure automatically called by GiD
#remove AfterMeshGeneration procedure to not corrupt other problemtypes
rename AfterMeshGeneration {}
}

proc AfterMeshGeneration { fail } {
#procedure automatically called by GiD
if { !$fail } {
CenterQuadraticNodes
}
}


proc CenterQuadraticNodes { } {
#assumed quadrilateral of 8 nodes, not checked
GidUtils::DisableGraphics
set OldCreateAllwaisNewPoint [.central.s info variable CreateAlwaysNewPoint]
.central.s process escape escape escape escape Utilities Variables CreateAlwaysNewPoint 1 escape

set elems [.central.s info mesh elements quadrilateral]
foreach {num n0 n1 n2 n3 n4 n5 n6 n7 mat} $elems {
foreach ni [list $n4 $n5 $n6 $n7] na [list $n0 $n1 $n2 $n3] nb [list $n1 $n2 $n3 $n0] {
set pa [lindex [.central.s info Coordinates $na mesh] 0]
set pb [lindex [.central.s info Coordinates $nb mesh] 0]
set pi [MathUtils::VectorSum $pa $pb]
set pi [MathUtils::ScalarByVectorProd 0.5 $pi]
.central.s process escape escape escape escape Meshing EditMesh MoveNode $ni NoJoin $pi
}
}

.central.s process escape escape escape escape Utilities Variables CreateAlwaysNewPoint $OldCreateAllwaisNewPoint
GidUtils::EnableGraphics

.central.s process escape escape escape escape Meshing MeshView escape
}

Regards
Enrique Escolano
----- Original Message -----
From: Robert MacDonald-Lewis
To: gidlist at gatxan.cimne.upc.es
Sent: Friday, February 20, 2004 2:29 PM
Subject: [GiDlist] Mesh problem


When meshing a structure I have modeled using quadrilateral elements with eight nodes, not all of the nodes are in the expected positions. Some are placed in the centre of elements whilst other expected to be equal distance between corner nodes of an element are offset to the right (I am using a structured mesh). Can anyone help me to solve this problem?



Galbraith Consulting Ltd
8 - 10 High Street
Laurencekirk

Kincardineshire
AB30 1AE

T +44 (0)1561-378383
robert at galbraithconsulting.co.uk
http://www.galbraithconsulting.co.uk


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