some grid doesn't have value
 

Dear all:
i tried to view one component fraction in POST. but some grids in the surface is not coloured as shown in this picture, they are still gray. I dont know why.
is there anyone who can tell me the reason?
many thanks in advance!
kind regards

Ji Guozhao
g.ji@uq.edu.au

You probably defined a plane which is right on a boundary. With numerical error on the mesh location that means 50% of the nodes lie on one side of the boundary and 50% on the other.

The best approach is to use the boundary as your object, not a plane. Otherwise move the plane into the domain by a tiny fraction, just enough to get beyond the numerical noise.