error message in blocking mesh
 

dear Foamers,

i got this message when i was working on OpenFOAM. can any one explain it to me.

--> FOAM FATAL ERROR:
Trying to specify a boundary face 4(4 5 6 7) on the face on cell 0 which is either an internal face or already belongs to some other patch. This is face 0 of patch 10 named internal-wall.

thanks.