background image
Code_Aster
®
Version
7.4
Titrate:
Operator
AFFE_CHAR_ACOU
Date:
20/12/04
Author (S):
NR. GREFFET, F. STIFKENS
Key
:
U4.44.04-G
Page
:
1/4
Instruction manual
U4.4- booklet: Modeling
HT-66/04/004/A
Organization (S):
EDF-R & D/AMA














Instruction manual
U4.4- booklet: Modeling
Document: U4.44.04



Operator
AFFE_CHAR_ACOU








1 Goal
To affect boundary conditions acoustic constant. The affected values do not depend
of any parameter and are complex values.
Product a structure of data of the type
char_acou
.
background image
Code_Aster
®
Version
7.4
Titrate:
Operator
AFFE_CHAR_ACOU
Date:
20/12/04
Author (S):
NR. GREFFET, F. STIFKENS
Key
:
U4.44.04-G
Page
:
2/4
Instruction manual
U4.4- booklet: Modeling
HT-66/04/004/A
2 Syntax

CH [char_acou] = AFFE_CHAR_ACOU
(
MODEL
=
Mo
[model]
VERI_DDL
=
/
“YES” [DEFECT]
/
“NOT”
I
PRES_IMPO
= F (
I
ALL = “YES”
I
NODE
= lno
[l_noeud]
I
GROUP_NO = lgno [l_gr_noeud]
I
NET
=
lma [l_maille]
I
GROUP_MA = lgma [l_gr_maille]
CLOSE =
pre
[C]
)
I
VITE_FACE
= _F (
/
ALL = “YES”
/
NET
=
lma [l_maille]
/
GROUP_MA = lgma [l_gr_maille]
VNOR =
vn
[C]
)
I
IMPE_FACE
= _F (
/
ALL = “YES”
/
NET
=
lma [l_maille]
/
GROUP_MA = lgma [l_gr_maille]
IMPE =
Z
[C]
)
I
LIAISON_UNIF=
_F (
/
NODE
= lno
[l_noeud]
/
GROUP_NO = lgno [l_gr_noeud]
/
NET
=
lma [l_maille]
/
GROUP_MA = lgma [l_gr_maille]
DDL =
“CLOSE”
)
);
background image
Code_Aster
®
Version
7.4
Titrate:
Operator
AFFE_CHAR_ACOU
Date:
20/12/04
Author (S):
NR. GREFFET, F. STIFKENS
Key
:
U4.44.04-G
Page
:
3/4
Instruction manual
U4.4- booklet: Modeling
HT-66/04/004/A
3 Operands
3.1 Operand
MODEL
MODEL = Mo
Name of the model whose mesh supports the elements of acoustic calculation.

3.2 Operand
VERI_DDL
VERI_DDL =/“YES”
/
“NOT”
Allows to check that the DDLs goods are well presented, i.e. here the DDL “CLOSE”
(cf [§3.4]).

3.3 Words
keys
PRES_IMPO
/
VITE_FACE
/
IMPE_FACE
3.3.1 Drank
Key words factors giving it natural of the conditions imposed on the specified elements (nodes, or
groups of nodes, meshs or groups of meshs).
I
PRES_IMPO
Allows to impose the DDL of pressure.
I
VITE_FACE
Allows to specify the vibratory field speed imposed in loading on elements
of border.
I
IMPE_FACE
Allows to specify the card of impedance imposed in boundary condition on elements
of border.
3.3.2 Operands
ALL
/
NODE
/
GROUP_NO
/
NET
/
GROUP_MA
Statement of the topological entities to which the loadings are applied, conditions with
limits.
background image
Code_Aster
®
Version
7.4
Titrate:
Operator
AFFE_CHAR_ACOU
Date:
20/12/04
Author (S):
NR. GREFFET, F. STIFKENS
Key
:
U4.44.04-G
Page
:
4/4
Instruction manual
U4.4- booklet: Modeling
HT-66/04/004/A
3.3.3 Operands
NEAR
/
VNOR
/
IMPE
CLOSE = pre
Value (complex) of the acoustic DDL of pressure (only DDL in acoustic modeling)
imposed on the nodes or groups of specified nodes.
VNOR = vn
Value (complex) of the component on the normal external with the meshs or groups of meshs
specified, the vibratory speed of the fluid.
IMPE = Z
Value (complex) of the acoustic impedance imposed on the meshs or groups of meshs
specified.

3.4 Word
key
LIAISON_UNIF
3.4.1 Drank
Key word factor allowing to impose the same value (unknown) on degrees of freedom of one
together of nodes.
3.4.2 Operands
NET/GROUP_MA/NODE/GROUP_NO
These operands make it possible to define a list of
N
nodes
NR
I
from which one eliminated the redundancies
(for MESH and GROUP_MA, they are connectivities of the meshs).
3.4.3 DDL
This operand can be worth in acoustic modeling, only the text “CLOSE”, defining only
degree of freedom allowed, acoustic pressure
p
.
The resulting imposed conditions are:
() ()
{
}
p NR
p NR
I
N
I
1
2
=
for
,…,


4 Example
cha = AFFE_CHAR_ACOU (MODEL = Mo,
VITE_FACE
=
_F (
NET
=
m4
,
VNOR = (
IH, 0.0135, 0. )),
IMPE_FACE
=
_F (
NET
=
m5
,
IMPE = (
IH, 442. , 0. )))
Note:
The complex values are provided under one of the two forms
IH
(real part, left
imaginary) or
MP
(module, phase in degrees).