When I run my file on CFD my object are connected (I can't put a different material)

[plb76bg]

I saw that there is different icon next to the 2 objects so maybe it's because of that I don't know (on the first picture).

As you can see the 2 corps are considered as only one object in one piece (on the second picture).

If you have any idea please send me a answer.

Thanks for reading.