UDS + conservation of initial mass
 

hi, I have the following problem. I use UDS to model species transport in an unsteady natural convection case. The unsteady term is just default and the flux function is mass flow rate. For some strange reason my initial species mass fraction is not conserved when I have zero flux at all boundaries. Has any of you ever encountered the same problem and if so, is there a solution for this? thanks, Hendrik-Jan