GiD forum

Hi

We are trying to develop a problem type for BEASY which is a
BEM code. The main problem appears to be defining the boundary
conditions.

Generally the condition we need to apply is like a face pressure on
an element. We wish to define the values of the pressure at each of
the nodes on the element as they may be different.
For example for a three node triangle we want to define the
pressure at each of the three nodes. Note we cannot apply it as a
nodal condition as pressure has to act over an area therefore it only
means something if applied over the surface of the element.
How do we define this in the cnd file?

Assuming we can do this successfully haw do we write the data
using the bas file.?

We want to create a record for each element with the condition
applied something like the following.

Elmt No FacePresNode1 FacePresNode2 FacePresNode3


Thanks for the help

Best regards

Bob Adey

Dr Robert Adey
Computational Mechanics BEASY
Ashurst Lodge, Ashurst,
Southampton, SO40 7AA, UK.
Tel: +44 (0) 238 029 3223
Fax: +44 (0) 238 029 2853
http://www.beasy.com

See BEASY on the www. www.beasy.com

Hello,

It is always easier to learn how to define conditions and
the .bas file by analysing a similar example.

You should check the example problemtypes that come with
the GiD distribution in the subdirectory: problemtypes

Search for conditions like: 'Surface-load' or something
similar.

Regards,

--
Compass Ing. y Sistemas Dr. Ramon Ribó
http://www.compassis.com ramsan at compassis.com
c/ Manuel Girona, 61 bajos tel. +34 93 204 10 82
08034 Barcelona, Spain fax. +34 93 204 19 09



-----Mensaje original-----
De: owner-gid at gatxan.cimne.upc.es
[mailto:owner-gid at gatxan.cimne.upc.es]En nombre de Bob Adey
Enviado el: miércoles, 01 de agosto de 2001 18:16
Para: gidlist at gatxan.cimne.upc.es
Asunto: [ GiDlist ] Problem type definition


Hi

We are trying to develop a problem type for BEASY which is a
BEM code. The main problem appears to be defining the boundary
conditions.

Generally the condition we need to apply is like a face pressure on
an element. We wish to define the values of the pressure at each of
the nodes on the element as they may be different.
For example for a three node triangle we want to define the
pressure at each of the three nodes. Note we cannot apply it as a
nodal condition as pressure has to act over an area therefore it only
means something if applied over the surface of the element.
How do we define this in the cnd file?

Assuming we can do this successfully haw do we write the data
using the bas file.?

We want to create a record for each element with the condition
applied something like the following.

Elmt No FacePresNode1 FacePresNode2 FacePresNode3


Thanks for the help

Best regards

Bob Adey

Dr Robert Adey
Computational Mechanics BEASY
Ashurst Lodge, Ashurst,
Southampton, SO40 7AA, UK.
Tel: +44 (0) 238 029 3223
Fax: +44 (0) 238 029 2853
http://www.beasy.com

See BEASY on the www. www.beasy.com

In GiD, the philosophy is to apply the conditions over the geometric entities (not directly over the mesh: remeshing these condition are lost)

If the condition is constant for all the nodes/elements generated from a surface, then
is too easy assign a pressure condition to these surface (transfered automatically to nodes or elements)

for example:
File: BEASY.cnd

NUMBER: 1 CONDITION: Pressure
CONDTYPE: over surfaces
CONDMESHTYPE: over elems
QUESTION: Pressure_Value
VALUE: 0
END CONDITION

File: BEASY.bas

*Set Cond Pressure *elems
*loop elems *OnlyInCond
Elmt *ElemsNum*\
*for(i=1;i=nnode;i=i+1)
*Cond(Pressure_Value)*\
*end for

*end elems

Note: another file BEASY.prb can be created for any problem type

If the value of the pressure on a node can be defined from your geometric position
(for example a hydrostatic pressure), then must be used a #FUNC# field of a condition.

NUMBER: 2 CONDITION: Hydrostatic_pressure
CONDTYPE: over surfaces
CONDMESHTYPE: over nodes
CANREPEAT: yes
QUESTION: Density:
VALUE: 0
QUESTION: Z_Water_Level:
VALUE: 0
QUESTION: AutoCalculatePressure#FUNC#(Cond(1,REAL)*(Cond(2,REAL)-z))
VALUE: AutoCalculate
END CONDITION


(The field AutoCalculatePressure contain the Density*(Z_Water_Level-Znode) calculated for each node)

*Set Cond Hydrostatic_pressure *nodes
*loop nodes *OnlyInCond
*nodesnum *Cond(AutoCalculatePressure)
*end nodes

In a small case, the user can apply condition values to a node directly.
(physically this pressure can be considered as is over the face of the parent element)

Best regards

----- Original Message -----
From: "Bob Adey" r.adey at beasy.com
To: gidlist at gatxan.cimne.upc.es
Sent: Wednesday, August 01, 2001 6:15 PM
Subject: [ GiDlist ] Problem type definition


Hi

We are trying to develop a problem type for BEASY which is a
BEM code. The main problem appears to be defining the boundary
conditions.

Generally the condition we need to apply is like a face pressure on
an element. We wish to define the values of the pressure at each of
the nodes on the element as they may be different.
For example for a three node triangle we want to define the
pressure at each of the three nodes. Note we cannot apply it as a
nodal condition as pressure has to act over an area therefore it only
means something if applied over the surface of the element.
How do we define this in the cnd file?

Assuming we can do this successfully haw do we write the data
using the bas file.?

We want to create a record for each element with the condition
applied something like the following.

Elmt No FacePresNode1 FacePresNode2 FacePresNode3


Thanks for the help

Best regards

Bob Adey

Dr Robert Adey
Computational Mechanics BEASY
Ashurst Lodge, Ashurst,
Southampton, SO40 7AA, UK.
Tel: +44 (0) 238 029 3223
Fax: +44 (0) 238 029 2853
http://www.beasy.com

See BEASY on the www. www.beasy.com


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