Transient thermal analysis

Gabriele Piscopo

Dear all,

I'm trying to perform a transient thermal analysis with Optistruct.

I have a component with a constant thermal flux. On this component I have also convection on a surface and a fixed temperature on another surface (like in the attached figure 'Problem description').

Here a brief description of the modelling phases:

• the ambient temperature for the convection element was modelled as SPC
• The heat flux was modelled using TLOAD1 card
• the initial temperature as TEMPD.

Firstly I try to simulate the model without the temperature boundary (Imposed temperature in the figure) and it works well. Then, I try to add also this boundary but it does not work. I imposed the temperature in the load collector containing the ambient temperature of convective element.

 

Where am I wrong? does this problem make sense? (I think that the initial temperature goes in contrast with the imposed temperature)

Thanks a lot,

Gabriele

Gildas_GUILLY

Hello Gabrielle,
Do you impose a 0K (or 0°C depending on your reference) to the nodes where you want to set the temperature (on the face and on the fluid), or is it a value different to 0 ?
If different to 0, a simple SPC will not be enough, and you will need to define SPCD+TLOAD1.

This is the way to do your problem the "cleaner" way (meaning the way that will work for all scenarios) :

• Boundary conditions : Use a load collector to store SPC on all nodes you are going to impose the temperature (meaning the fluid node and the nodes on the constant face).

• For the face with constant temperature :
• A load collector containing SPCD with a value of 1 (unitary) on all nodes of the face
• A curve (with TABLED1 card image) defining the temperature over time for the face
• A TLOAD1 locad collector to define the dynamic loading, combining the 2 load collector above.

• For the convection :
• A load collector containing SPCD with a value of 1 (unitary) on your fluid node
• A curve (with TABLED1 card image) defining the temperature over time for the fluid
• A TLOAD1 locad collector to define the dynamic loading, combining the 2 load collector above.

• For the flux:
• A load collector containing the flux load on the faces
• A curve (with TABLED1 card image) defining the evolution of the flux over time.
• A TLOAD1 locad collector to define the dynamic loading, combining the 2 load collector above.

• And finally you need a DLOAD loadcollector to combine your 3 TLOADs, and to be called by your loadstep.

Gildas

Gabriele Piscopo

Gildas GUILLY_21156 said:

Hello Gabrielle,
Do you impose a 0K (or 0°C depending on your reference) to the nodes where you want to set the temperature (on the face and on the fluid), or is it a value different to 0 ?
If different to 0, a simple SPC will not be enough, and you will need to define SPCD+TLOAD1.

This is the way to do your problem the "cleaner" way (meaning the way that will work for all scenarios) :

• Boundary conditions : Use a load collector to store SPC on all nodes you are going to impose the temperature (meaning the fluid node and the nodes on the constant face).

• For the face with constant temperature :
• A load collector containing SPCD with a value of 1 (unitary) on all nodes of the face
• A curve (with TABLED1 card image) defining the temperature over time for the face
• A TLOAD1 locad collector to define the dynamic loading, combining the 2 load collector above.

• For the convection :
• A load collector containing SPCD with a value of 1 (unitary) on your fluid node
• A curve (with TABLED1 card image) defining the temperature over time for the fluid
• A TLOAD1 locad collector to define the dynamic loading, combining the 2 load collector above.

• For the flux:
• A load collector containing the flux load on the faces
• A curve (with TABLED1 card image) defining the evolution of the flux over time.
• A TLOAD1 locad collector to define the dynamic loading, combining the 2 load collector above.

• And finally you need a DLOAD loadcollector to combine your 3 TLOADs, and to be called by your loadstep.

Gildas

Dear Guilly,

thanks for the reply.

after modelling the problem with your suggestions I  obtained the following error...

See next message about line 9688378 from file:
/ASTER/analisi termica/tip_altair_forum/test_flusso_temperatura.fem
"DLOAD 10 1.0 2 1.0 7 1.0 9"

*** ERROR # 1000 *** in the input data:
Incorrect data in field # 3.

 

Do you know why? It could depend on 'Type' (figure attached)?

Thanks a lot,

Gabriele

Gildas_GUILLY

Gabriele Piscopo said:

Dear Guilly,

thanks for the reply.

after modelling the problem with your suggestions I  obtained the following error...

See next message about line 9688378 from file:
/ASTER/analisi termica/tip_altair_forum/test_flusso_temperatura.fem
"DLOAD 10 1.0 2 1.0 7 1.0 9"

*** ERROR # 1000 *** in the input data:
Incorrect data in field # 3.

 

Do you know why? It could depend on 'Type' (figure attached)?

Thanks a lot,

Gabriele

Gabrielle,
It looks like you forgot to enter a value for S in the definition of the DLOAD load collector.

Gildas

Gabriele Piscopo

Gildas GUILLY_21156 said:

Gabrielle,
It looks like you forgot to enter a value for S in the definition of the DLOAD load collector.

Gildas

I'm sorry but now i have another error:

A fatal error has been detected during input processing:

*** ERROR 14: Missing EXCITEID # 6 referenced by TLOAD1_TEMP # 6.

Gildas_GUILLY

Gabriele Piscopo said:

I'm sorry but now i have another error:

A fatal error has been detected during input processing:

*** ERROR 14: Missing EXCITEID # 6 referenced by TLOAD1_TEMP # 6.

As explained in the error message, you either have forgotten to enter the EXCITEDID in the TLOAD, or you have used a wrong loadcollector/load TYPE association.
For your 3 TLOAD, the TYPE should be DISP for the first 2, LOAD for the third one.

Gildas