[ GiDlist ] Computational Box with Shyne

[Odland, Bradly A.]

Well I have tried to get the unique volume around a hole that has zero
thickness.

What happens now is the meshing nears the end and the cpu usage is 100%
constant and the disk is chugging away. The machine runs out of virtual
memory. Is generating a mesh of the type discussed below too much for a
machine with Windows 2000 800 Mhz with 128 Meg Ram ?

Here are the steps:

1. Created a box with NURBS surfaces
2. Imported the DXF of the sail
3. Placed it inside the box
4. Simplified the Sail to points describing the panels
5. drew lines between the points.
6. Created new nurbs surfaces
7. Copied the surfaces translate, 0,0,0 no duplication of entities
8. Created contact volume for each panel (10 in all)
9. Created the control volume from box surfaces
10. Created a hole from the contact volumes in the control volume
11. Set no mesh to the contact volumes
12. Set up the problem like the third tutorial sample in the PDF
13. Generated mesh and it goes until the GID crashes from Windows adjusting
virtual memory.

Any thoughts would be appreciated.

TIA

Brad Odland
Odland Sails

-----Original Message-----
From: Ramon Ribó Rodríguez [mailto:ramsan at cimne.upc.es]
Sent: Monday, December 11, 2000 8:06 AM
To: gidlist at gatxan.cimne.upc.es
Subject: Re: [ GiDlist ] Computational Box with Shyne



Hello,

To create a box you can do it "manually" by using:
Geometry-Create-Line... or
Geometry-Create-Object-Prism

If it is something that must be repeated every time, as it seems to be
your
case, it is better to implement a simple procedure in TCL-TK to make it
automatically. Several 'problemtypes', specially related to CFD, have
already
done it to create the control box.

If your are going to perform an analysis on a sail, be very careful in
the
sense that it has a thickness close to zero. It can give several meshing
problems to have a volume with a hole that has a 'volume' of zero.

Previus analysis made with GiD on sails use the following approach:

Sail is discretized with a double surface that has as boundary the same
set
of lines. It means that the closed boundary of the two surfaces is the same
and
the two surfaces have the same geometric representation but are two
different
entities. One of them represent the windward and the other represent the
heeward. To do so, there can be used the following options:
Utilities-Copy ( a 0,0,0 translation with option 'duplicate
entities' unset)
Utilities-Collapse-Lines (and select the boundary lines).

Then, the control volume is divided into two volumes by adding additional
surfaces. In this way, the hole of zero thickness is avoided. If there are
two
sails, the aproach is the same having two doubled surfaces and 3 control
volumes.

GiD version 6 has implemented and special option that permits to have a
unique control volume around a zero thickness hole (that would be the sail).
To
use it, create the hole with the same doubled surfaces aproach than before
and
create the volume with a hole. After this, do:
-Geometry-Create-Contact volume (select the 2 double surfaces).
-Meshing-Mesh criteria-No mesh-Volumes (and select the created
contact
volume).


Hope it helps,


On Thu, 07 Dec 2000, you wrote:
I would like to know how to create a computational box that has a center
of
0 0 0.

What does LPB mean?

I am trying to put a sail into the box and make it a hole?


Brad
--
Centre Internacional de Mètodes Dr. Ramon Ribó
Numèrics en Enginyeria
http://gid.cimne.upc.es/ramsan ramsan at cimne.upc.es
C/ Gran Capitan s/n,
Modulo C1, Campus Norte UPC, tel. +34 93 401 74 03
E-08034 Barcelona, Spain fax. +34 93 401 65 17