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

problem description.PNG

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