Hi... my problem involve multicomponent mixing... i've two species H2, Air, they flows in separeted channel but they comunicate by a porous media... i've obtained a solution but there are many warnings in the file.inf

iteration number 1 1)warning 042 2)warning 044 3)warning 009 (the value of scalar sc2 in cell ...is below the minimum.... any advise for this kind of problem...?

It only display in iteration 1, for your initial condition of calculated component is too lower. It's nothing important.

Scalar transports by convection and diffusion. Either steady state or transient, convection effect only goes several cell layers in each iteration or time step depending on velocity. But diffusion equation is implicit, and any disturbance should spread out instantly to the whole field. If it is far away from source, the concentration should be nearly zero, and thus give a below the minimum value. In steady state SIMPLE algorithm, this should disappear after some iterations; otherwise, check mesh quality. And similarily, in transient process.