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

Organization (S): EDF-R & D/AMA, DeltaCAD
Handbook of Utilization
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).
Handbook of Utilization
U3.14 booklet: Mechanical finite elements 3D
HT-66/05/004/A

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

1 Discretization

1.1
Degrees of freedom

Finished element
Degrees of freedom (with each node node)

MEFL_… (3d_FLUIDE)
PRES: 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:

The coupling with a structure with a grid in elements COQUE_3D forces 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

Handbook of Utilization
U3.14 booklet: Mechanical finite elements 3D
HT-66/05/004/A

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

2 Loadings
supported

The loadings available are as follows:

· PESANTEUR
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 the linearized deformations key word “PETIT” 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.
Handbook of Utilization
U3.14 booklet: Mechanical finite elements 3D
HT-66/05/004/A

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

Intentionally white left page.
Handbook of Utilization
U3.14 booklet: Mechanical finite elements 3D
HT-66/05/004/A

Outline document