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Thermal analysis
code_aster, salome_meca course materialGNU FDL licence (http://www.gnu.org/copyleft/fdl.html)
Outline
1. Overview of the main features
2. A simple example of thermo-mechanical computation
3 - Code_Aster and Salome-Meca course material GNU FDL Licence
A simple example : pipe in thermal equilibrium
We want to know the temperature field in the thickness of the pipe
40°C
15°C
Infinite pipe
Load : a temperature field on each side
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4 - Code_Aster and Salome-Meca course material GNU FDL Licence
Code_Aster : main features for thermics
Pipe in thermal equilibrium : isothermal values
Frequently used as a prerequisite to a mechanical calculation
Example : pipe with prescribed temperature on each side
Thermic calculation
Mechanical calculation
Final displacement and circumferential pipe stresses
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Outline
1. Overview of the main features
2. A simple example of thermo-mechanical computation
6 - Code_Aster and Salome-Meca course material GNU FDL Licence
What is the problem to be solved?
The problem can be :
AFFE_MODELE ( ...PHENOMENE = ‘THERMIQUE’... )
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stationnary transient
linear
non-linear
0=sλΔTTρC 0=sλΔT
0)()( =TsΔTTλ 0)()()( =TsΔTTλTTρC
equation in the bulk
stationnary transient
linear
non-linear
supported Neumann boundary conditions
xtf=dn
dTλ ,
Tf=dn
dTTλ )(
7 - Code_Aster and Salome-Meca course material GNU FDL Licence
What is the problem to be solved?
The problem can be :
AFFE_MODELE ( ...PHENOMENE = ‘THERMIQUE’... )
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stationnary transient
linear THER_LINEAIRE
ETAT_INIT ETAT_INIT
non-linear THER_NON_LINE
ETAT_INIT ETAT_INIT
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Available finite elements
AFFE_MODELE ( … PHENOMENE = ‘THERMIQUE’
… MODELISATION = ‘XXXX’ ...) )
3D / AXIS / PLAN
3D_DIAG / AXIS_DIAG / PLAN_DIAG
regularization during heat shock
splitting of quadratic elements in 2D
splitting not avalaible in 3D
COQUE / COQUE_PLAN / COQUE_AXIS (linear)
thermal shell "thin" structural elements
temperature field in the thickness : 3 degrees of freedom (Tsup, Tinf and Tmiddle)
Example of a sudden cooling :
289°C
20°C
T
temps
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9 - Code_Aster and Salome-Meca course material GNU FDL Licence
Precautions for use in thermics
nnnn TTTTt
C
)1()(
.11
Time discretization with the -méthode.
Ability to change with PARM_THETA
In case of unstable results, in spite of lumped elements :Minimal time step proven to yield stable results, good start to increase from :
λΔxρC
Δt
mesh
16 3
2
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10 - Code_Aster and Salome-Meca course material GNU FDL Licence
Material behavior
DEFI_MATERIAU
At least these two characteristics:
3 main materials :
+ other specific materials For concrete : drying, hydratation ... etc
For metals : metallurgical transformations, hardness ... etc
Thermal conductivity
Heat capacity
PρC
)(T )(T
THER Linear isotropic
THER_ORTH Linear orthotropic (definition of in 3 directions)
THER_NL Non-linear behaviour : one has to define or and
!! THER_NON_LINE has to be used
)(TρCP
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11 - Code_Aster and Salome-Meca course material GNU FDL Licence
Boundary conditions and loadings (1)
AFFE_CHAR_THER (...)
AFFE_CHAR_THER_F (...)
Full list : https://www.code-aster.org/V2/doc/v14/fr/man_r/r5/r5.02.02.pdf
Boundary conditions (Dirichlet)
Imposed temperatures function of time and space TEMP_IMPO
Linear relationships between the nodal temperatures
LIAISON_DDL
LIAISON_GROUP
LIAISON_MAIL
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https://www.code-aster.org/V2/doc/v14/fr/man_r/r5/r5.02.02.pdf
12 - Code_Aster and Salome-Meca course material GNU FDL Licence
Boundary conditions and loadings (2)
Loadings (Neumann)
Natural convection (Fourier law) ECHANGE
Heat exchange between walls ECHANGE_PAROI
Normal imposed flux : constant or
function of time and space FLUX_REP
Non linear normal flux : function of
the temperature
FLUX_NL
RAYONNEMENT
Heat source SOURCE
TTextth=dn
dTTλ
)Th(T=dn
dTλ
1
1121
x)f(t,=dn
dTλ(T)
f(T)=dn
dTλ(T)
t)s(x,
Non-linear only
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13 - Code_Aster and Salome-Meca course material GNU FDL Licence
Is the problem well defined?
Résults of a stationnary calculation STATIONNAIRE ='OUI'
A constant temperature VALE = T0
A known temperature field CHAM_NO = …
for example, created with CREA_CHAMP
The result of another thermal calculation A result concept (EVOL_THER = resu)
+ chosen time (NUME_ORDRE or INST )
For a stationnary calculation : YES
For a transient calculation : NOA condition is missing : the temperature at the initial time
Defined in THER_LINEAIRE or THER_NON_LINE with ETAT_INIT4 possibilities :
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14 - Code_Aster and Salome-Meca course material GNU FDL Licence
Post-processing options
What's the result of THER_LINEAIRE / THER_NON_LINE ?
By default : only the nodal temperatures
How to get the thermal fluxes ?
With CALC_CHAMPFLUX_ELGA
FLUX_ELNO
FLUX_NOEU
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And mechanics?
How to take into account the temperature field in the mechanical calculation?
The mesh to be used in mechanics must be different from that used for thermics. For two main reasons:
A linear mesh is better in thermics, while rather quadratic in mechanics
Areas of interest are different => the refined areas are different
One must project the temperature field on the mesh used for mechanics
PROJ_CHAMP ( … )
In AFFE_MATERIAU (...AFFE_VARC=_F( NOM_VARC = 'TEMP',
EVOL = EVOTH,
VALE_REF = 20. )
...)
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Outline
1. Overview of the main features
2. A simple example of thermo-mechanical computation
17 - Code_Aster and Salome-Meca course material GNU FDL Licence17
A simple example : pipe in thermal equilibrium
Add a stage from computation assistant → allows to quickly start a computation
Pick mesh Select FEM modelling Enter material properties
Define loading and
boundary conditions
Specify path for output result
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A simple example : pipe in thermal equilibrium
Datasettings panel :
lists created commands
Edit command panel :
adjust command data
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A simple example : pipe in thermal equilibrium
Results tab : select field
Get live field visualization
Results tab : select component
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And mechanics ?This time, use « thermo-mechanical analysis »
assistant
Enter mechanical material
properties, including expansion coefficient
Enter initial temperature, even for stationnary computation
(useful for thermal induced strains)
Enter time or pseudo-time
discretization
Goes through same steps as before, plus…
Enter FEM modelling for
mechanical computation
Enter mechanical loading and
boundary conditions
21 - Code_Aster and Salome-Meca course material GNU FDL Licence21
And mechanics ?
Uncheck ETAT_INIT
in THER_LINERAIRE
Tip : the presence of ETAT_INIT keyword indicates a transient computation.
Otherwise, it is stationnary.
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And mechanics ?
Results tab : select field
Get live field visualization
on the deformed shape
Results tab : select component
23 - Code_Aster and Salome-Meca course material GNU FDL Licence23
To go further…
Start a computation taking your inspiration from an existing testcase
For instance :
SSLP117 Provide an analytical temperature field as input to mechanical computation
TPLP107 Prescribed fluxes, temperature or source variable in space
TTNL04 Prescribed fluxes variable in time
FORMA30,
FORMA21Transient thermal computation
SSNV301 Elasto-plastic mechanical computation
And much more at https://www.code-aster.org/V2/doc/v14/fr/index.php?man=cas-test
https://www.code-aster.org/V2/doc/v14/fr/index.php?man=cas-test
End of presentation
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