Make an outward-flowing mass constraint in 2D Feflow

G'day,

What do I need to set in order to allow mass-concentration to expand past the mesh limit?

Example;

In the picture below, the mass-concentration boundary node is clearly prohibiting the 'normal' movement of the seawater.

The node is currently set to a mass-concentration of 200 mg/L. The plume is about 20000 mg/L.

I'm sure this is related to the min/max mass-flow constraints, but I can't work out the right parameters :(

[img width=140 height=200]https://i.imgur.com/XApIeEB.png[/img]

Could you please attach the picture to your post?

Done - sorry. Didn't see the option on the first pass.

If I understand you correctly, you want to allow mass flowing out of the system (model domain) and prohibit mass entering the system. If this is true, you can use a fixed mass Boundary Condition (type Dirichlet) on top of a flow Boundary Condition. Then, you may constraint the mass Boundary Condition with a minimum mass flow of 0 g/d as you already indicated. In this configuration, the Boundary Condition for mass is only active as long as water is entering the system. If water leaves the system, mass is transported out by the advective mass transport component (convective formulation of the transport equation).