Vented brake disc problem
 

Hi,

I am new to CFX and trying to simulate temperature change in a vented brake disc and a brake pad.

So there are 4 domains: a rotating solid domain (disc) with a rotating fluid domain (air) filling the passages which have walls normal to rotating velocity, a stationary solid domain (pad) and a stationary fluid domain. Heat source is set on pad side of the disc-pad interface. Everything seems to be working at the moment except the rotating solid domain and interfaces.

http://www.cfd-online.com/Forums/att...1&d=1444468337

The surface of disc is divided into two parts: one is solid-solid interface with stationary pad and the other is fluid-solid interface with stationary air. I set the frame change option to transient rotor/stator and it does not work. I may have a clue why it does not work but I cannot figure out how it can be fixed. Do I have to remove brake pad model or is there a better way of doing it?

Cheers

Your rotor interface is connecting to both the pad and the air. CFX cannot handle this - a surface can only be in one interface.

You are going to have to chop your rotor surface into two surfaces; the bit which contacts the pad and the bit which contacts the air. Then each bit of the rotor is only part of a single interface. Note this means the Transient Rotor Stator approach will not work, you are going to have to use frozen rotor or something like that.

Also: You will need CFX V15 or V16 for this model? Earlier versions of CFX do not support convection of heat in solids due to motion.

Have you tried Non overlapping conditions of domain interface?

Non-overlapping conditions allows you to specify an alternate boundary condition to apply in the non-overlapping locations. It does not allow you to specify that a different interface applies. At least that was the case last time I looked.

Thank you for the reply. I did chop the rotor surface and tried frozen rotor, heat was generated locally and did not spin. I may missed something there so I will check it again when I got access to CFX (V16).

I did not try non-overlapping conditions, I think an alternate boundary condition won't help in this case.

If we create interface between all of rotating solid face and stationary air domain, then the portion of surface between pad and solid is nonoverlapping for this interface...so we can set heat flux at this nonoverlapping condition...
I have not tried.. Plz check.. I will check tomorrow and tell you

I will try it tomorrow when I get access to CFX. Thanks a lot

Yes, that should work. But the heat transfer in the disc will not be coupled with the heat transfer in the pad. Whether that is important or not is up to you to determine - my guess is it probably is not important so this approach is likely to be valid.

It works! But is there a way to include heat transfer between disc and pad?

Oh nice..u can give the total heat flux at the overlapping condition rite? 'to include heat transfer' means wat? Can u elaborate?

My post #2 answers this question.

If I create a interface between disc surface and air to use non overlapping conditions, there is no faces left on the disc surface to create interface between disc and pad for overlapping conditions. Thus the heat transfer in disc is independent to heat transfer in pad.

I will give frozen rotor a try.

Thank you guys so much for your help!