Learning Forum

[klara.marek]

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Hello!

I was wondering if it was possible to simulate surface to surface radiation in Discovery Explore Mode in a thermal Fluid Flow simulation.

The model I am trying to create is described in the above picture: there is a metal pin surrounded by a tube (length in z direction is 50mm). The material in the tube is supposed to be modeled as a vacuum – so I created a fluid with low density and very low thermal conductivity in order to mimic this fluid. The temperature on the outer surface of the tube is supposed to be steady and the temperature of the pin surface/ inner surface of the fluid has a higher temperature and an emissivity. When running a time-dependent simulation of this problem I’d expect the temperature of the inner surface to sink to the level of the outer surface due to the radiation flux.

Now I understand that I cannot model this solid/ fluid interaction in Discovery Explore Mode. I was wondering though if it was possible to use the possible boundary conditions to recreate those circumstances, only modeling the fluid domain.

For the outer surface I choose a wall with steady temperature, front and back plane of the domain are Insulated Freeslip walls to mimic a symmetry boundary condition. (See model attached)

Now for the inner surface I found the convection boundary condition with radiation. If I understood correctly, the convection temperature and specific convection coefficient are relevant if there was a fluid flow past this boundary, causing a heat flux. This is not the case, so I set both to zero. (Please let me know if I misunderstood this boundary condition!) Now I was wondering if the radiation condition is applicable in this case by setting the specific radiation temperature to the temperature of the pin and using the emissivity as given in the description. Or is this only applicable if there is radiative flux onto the boundary and not from the boundary into the fluid domain and onto the outer wall.

Please let me know if I am misunderstanding the radiation boundary condition and if it is not possible to simulate the surface (inner tube boundary) to surface (outer tube boundary) radiation (since I am not getting the results I was expecting I am very much guessing I made a mistake in the setup or it is not possible to do this simulation).

Thank you very much for all comments, clarifications and inputs regarding this problem!

[Naresh Patre]

Hello Klara

Surface to surface radiation is currently not possible in Discovery. We can only model radiation from a wall to surrounding blackbody. Please check out the details about "Convection and Radiation" boundary condition in the help document at below mentioned link:

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v211/en/discovery/UDA/user_manual/physics/fluids/topics/r_fluids_wall_thermal.html