S2S Model
 

In the process of calculating view factor

I have some points can't understand

a) what 'faces per surface cluster' means

b) how do we decide which surface is not necessary for view factor calculation

Thanks in advance for your help

Hello itsme_kit,

a) Faces/clusters is the number of cell-faces that are grouped in a cluster: for example, if you set 100 faces/clusters every cluster will have 100 faces (100 elements of your mesh); with this option you are able to decrease computational cost.

b) you need to include in view-factor calculation all the important surfaces of your system: of course there isn't a general rule, it depends on your problem.
I suggest excluding smallest surfaces and remember that if you have coupled surfaces (solid-fluid interfaces for example, with shadows-wall), you have to include only the face of the fluid in the view-factor calculation (so you can exclude solid faces)

Regards

Thanks for your explanation, Bionico

Just expand first question a little further

It seems that the more number of face/cluster we set up, the less accurate results we will get.

Does it make sense?

You're right: bigger the cluster is, less accurate the calculation of radiating heat flux is.
Imagine the clustering like the meshing: increasing faces/cluster will generate a coarser resolution of radiating heat flux

Regards