how to configurate wall and shadow wall
 

here is my question.I create a mesh in gambit .I have a solid zone adjacent to a fluid zone. I import this mesh to fluent, I get a wall and a wall-shadow between these 2 zones. my model is energy on,laminar and discrete ordinates. What is this wall-shadow zone and why does Fluent create this? what material property should I assign to wall amd wall-shadow respectively?the "internal emissivity" in both walls need fill out??thanks!

Fluent creates a shadow to a wall if that wall lies between 2 different cellzones which most of the time occurs at the interface between a solid zone and fluid zone (not always).
Whatever BC you give to the wall needs to be defined for the shadow (temperature, heat flux, emissivity etc)

Regards
Luke