Help needed on boundary condition/Floating point error: Invalid number
 

I am working on binary fluidized bed reactor with heat transfer and chemical reaction.
I have 4 phases before reaction and 7 phases after reaction, i am using eulerian model in Fluent, now the problem is when i try to introduce another phase with air(primary) phase at the column inlet defined (velocity inlet) in Fluent i get error:
Floating point error: invalid number
i have even reduced the time step size to as low as 1e-6 and checked other things which could give this result but i have not been able to rectify the problem.Please help.thank you

I think i´ve read somewhere those sort of errors usually happen when strong gradients are found in some parts of your mesh (large cells ).
What about smoothing (refining) your mesh in those areas?
Sorry if it´s just a simple answer, but wish it could help.

thank you Daniel, you r right about that but i my case this doesn't seems to be the problem.....anyways thank you