I've successfully modelled a transport of coupled dilute species, electrostatics and deformed geometry problem in 1D and I'm now trying increase it to 2D. I'm having an issue with concentrations going negative in a particular regions of my model, depsite using the same boundary conditions that were successful in my 1D model. At the moment I am ignoring the deformed geometry and trying to solve the stationary case to use as initial values for the deforming time resolved case. The stationary model converges, but with the negative concentration region.
What's interesting is that if I use this erroneous solution as the initial condition for a time resolved study of some arbitrary time I get a reasonable looking result for all time steps (i.e. no negative concentrations and good agreement with the 1D model). So the time-resolved solution for what should be a static system does indeed look static but the stationary solver on the same system will not give this result.
Does anyone have any suggestions as to why this would be?