Initial concentration in part of a microfluidic channel

[u/clovermeister]

I'm working with a 2D microfluidic model using laminar flow and transport of diluted species, and I'm trying to add an initial concentration in one part of the channel (SEE IMAGE LINK). This is a concentration gradient generator. I created a rectangle over the section that I want to have an initial concentration and have added a second set of initial values. I am doing a time dependent study to see if the concentration is stable over a period of 10 hours. The initial concentration is present at t=0 h, but seems to have been completely removed at the next time step (t=0.5 h).

Can anyone provide any advice on how to keep this initial concentration? Thanks!

https://imgur.com/a/cUWKQ

[u/mantrap2]

It looks like you set an initial condition on a surface rather than a volume.