Discussion Forum

I am trying to characterize concentration gradients that form in a closed system as a function of time. I have a 2D simulation where in I have defined Initial values of concentration and used no flux conditions at the boundary. I am unable to think of any more boundary conditions since I am trying to solve for time -varying fick's diffusion equation. I have an initial condition that was given by initial values (1st order in time) and the no-fluxes at boundaries (2nd order in space in x and y-direction). Can anyone tell me if I am missing anything as the results I am getting are a little weird. I get linear gradients through my ROI which kind of doesn't make sense as the diffusion should slow down with time and it should follow more of an e^-x kind of curve (which I have successfully tested experimentally). Any insights would be really helpful.

PS: I tried attaching my model for further reference but I got an error message - 'file size error' (I am guessing my model file is too big to be uploaded). I can share my model with you via google dropbox if you think you need to take a look at the model!