Mesh dependency !

Hello,

I wanted to ask about meshing a 3D problem.

I'm doing a validation for 3D channel with radiation between the inner side of the channel (surface to surface radiation). I'm facing a problem when I increase the order of the mesh, for example, I got similar result to the paper when I use coarse mech but when I increase number of elements in the mesh such as normal mesh I got different result !!

So what do you think I can do to avoid mesh dependency ?

I really need your help.

Thank you so much in advance.

Regards,

Shaikha