Negative concentration

Hy,

I'm running a transient flow/transport model. So the borders of the contamianation plume are negative in mass. This situation is obviously impossible. Why this results and how to resolve this problem. If I have to put a constraint, please specify wich one.

Thanks ,

Michael

Negative concentrations indicate an instable model setup. You are right that they are physically impossible. However, they are not suppressed by FEFLOW to tell you that something is wrong with your model. Please try to refine the mesh as a first step as the most likely reason for oscillations in a solute transport model is an insufficient spatial discretization.