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Code_Aster
®
Version
7.4
Titrate:
Modelings
3d_FLUIDE
,
FLUI_STRU
,
2d_FLUI_PESA
Date:
01/06/05
Author (S):
NR. GREFFET, F. LEBOUVIER
Key
:
U3.14.02-E
Page
:
1/4
Instruction manual
U3.14 booklet: Mechanical finite elements 3D
HT-66/05/004/A
Organization (S):
EDF-R & D/AMA, DeltaCAD















Instruction manual
U3.14 booklet: Mechanical finite elements 3D
Document: U3.14.02



Modelings
3d_FLUIDE
,
FLUI_STRU
,
2d_FLUI_PESA



Summary:

This document describes for modelings
3d_FLUIDE
,
FLUI_STRU
,
2d_FLUI_PESA
:
·
degrees of freedom carried by the finite elements which support modeling,
·
the related meshs supports,
·
supported loadings,
·
nonlinear possibilities,
·
case-tests implementing modelings.

Modelings
3d_FLUIDE
(elements of volume) and
FLUI_STRU
(elements 2D of interaction fluid-structure)
correspond to the linear formulation of the coupled problem allowing the study of the vibratory behavior of one
structure in the presence of a nonviscous, compressible fluid [R4.04.01]. The free face is taken into account
by modeling
2d_FLUI_PESA
(surface elements).
background image
Code_Aster
®
Version
7.4
Titrate:
Modelings
3d_FLUIDE
,
FLUI_STRU
,
2d_FLUI_PESA
Date:
01/06/05
Author (S):
NR. GREFFET, F. LEBOUVIER
Key
:
U3.14.02-E
Page
:
2/4
Instruction manual
U3.14 booklet: Mechanical finite elements 3D
HT-66/05/004/A
1 Discretization
1.1
Degrees of freedom
Finished element
Degrees of freedom (with each node node)
MEFL_… (3d_FLUIDE)
NEAR
: pressure
PHI
: fluid potential of displacement
MEFL_FACE… (3d_FLUIDE)
PHI
: fluid potential of displacement
MEFS_… (FLUI_STRU)
DX, DY, DZ
: components of structure displacement
PHI
: fluid potential of displacement
MEFP_FACE… (2d_FLUI_PESA)
DZ
: deflection of the free face
PHI
: fluid potential of displacement
1.2
Net support of the matrices of rigidity
Modeling Nets Element
finished
Remarks
3d_FLUIDE TETRA4
MEFL_TETRA4
TETRA10
MEFL_TETRA10
PENTA6
MEFL_PENTA6
PENTA15 MEFL_PENTA15
HEXA8 MEFL_HEXA8
HEXA20 MEFL_HEXA20
HEXA27 MEFL_HEXA27
FLUI_STRU TRIA3
MEFS_FACE3
TRIA6 MEFS_FACE6
QUAD4 MEFS_FACE4
QUAD8 MEFS_FACE8
QUAD9 MEFS_FACE9
2d_FLUI_PESA TRIA3 MEFP_FACE3
TRIA6 MEFP_FACE6
QUAD4 MEFP_FACE4
QUAD8 MEFP_FACE8
QUAD9 MEFP_FACE9

Note:
Coupling with a structure with a grid in elements
COQUE_3D
force to net the interface
fluid-structure with elements
QUAD8
(and not
QUAD9
). The fluid massive field is thus
with a grid in
HEXA20
(and not
HEXA27
). Indeed, the coupling fluid-structure is done on the DDL
of displacement only, for the solid.

1.3
Net support of the loadings
Modeling Nets Element
finished
Remarks
3d_FLUIDE TRIA3
MEFL_FACE3
TRIA6
MEFL_FACE6
QUAD4
MEFL_FACE4
QUAD8
MEFL_FACE8
QUAD9
MEFL_FACE9
background image
Code_Aster
®
Version
7.4
Titrate:
Modelings
3d_FLUIDE
,
FLUI_STRU
,
2d_FLUI_PESA
Date:
01/06/05
Author (S):
NR. GREFFET, F. LEBOUVIER
Key
:
U3.14.02-E
Page
:
3/4
Instruction manual
U3.14 booklet: Mechanical finite elements 3D
HT-66/05/004/A
2 Loadings
supported
The loadings available are as follows:
·
GRAVITY
Allows to apply a loading of the gravity type.
Supported modeling:
2d_FLUI_PESA
·
VITE_FACE
Allows to specify the field speed vibratory imposed in loading on elements of
border.
Supported modeling:
3d_FLUIDE
·
IMPE_FACE
Allows to specify the card of impedance imposed in boundary condition on elements of
border.
Supported modeling:
3d_FLUIDE
·
“ONDE_FLUI”
Allows to apply an amplitude of pressure of sinusoidal incidental wave arriving normally
with a face.
Supported modeling:
3d_FLUIDE

3 Possibilities
non-linear
3.1
Laws of behaviors
The only relation of behavior available in
DYNA_NON_LINE
, for modeling
FLUI_STRU
under
COMP_INCR
is
RELATION “ELAS”
(Cf [U4.51.11]).
3.2 Deformations
Only linearized deformations key word
“SMALL”
under
DEFORMATION
are available in
relations of behavior (cf [U4.51.11]).

4
Example of implementation: case-tests
·
3d_FLUIDE
AHLV100B [V8.22.100]: A rectilinear guide of wave at anechoic exit of which medium of
propagation is “normal” air, is excited by a harmonically vibrating piston. Calculation
consist in determining the field of acoustic pressure of the harmonic answer.
FDLV111A [V8.01.111]: Absorption of a wave of pressure created by a piston in a column
fluid.
·
FLUI_STRUC
FDLV111A [V8.01.111]: Absorption of a wave of pressure created by a piston in a column
fluid.
FDNV100A [V8.01.111]: Analyze shaking of a water tank with deformable wall
rubber band.
·
2d_FLUI_PESA
FDNV100A [V8.01.111]: Analyze shaking of a water tank with deformable wall
rubber band.
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Code_Aster
®
Version
7.4
Titrate:
Modelings
3d_FLUIDE
,
FLUI_STRU
,
2d_FLUI_PESA
Date:
01/06/05
Author (S):
NR. GREFFET, F. LEBOUVIER
Key
:
U3.14.02-E
Page
:
4/4
Instruction manual
U3.14 booklet: Mechanical finite elements 3D
HT-66/05/004/A

























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