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Hi,

Does COMSOL treat the nodes at the boundary also as unknowns?

I am trying to solve colloid transport inside a pipe with constant concentration boundary condition at the inlet. The unknown is concentration. There is sharp gradient in the concentration between the boundary node and the node next to that in the flow direction. I use very fine mesh.
If I plot the concentration at the inlet boundary using domain plot parameters, it is showing whatever the boundary condition I have given (Dirichlet) . But when I use cross-section plot parameters dialogue box to specify the line plot and plot the concentration at the inlet boundary, it is showing wrong values of boundary condition. Also the plotted values at the boundary changes with time where as the original B.C. is constant. In the data exported also the values at the points in the inlet boundary are different from my boundary condition.

So does comsol interpolate from the results to find the value of variable at the boundary if we give the co-ordinates?

Does anybody know why is this problem happening?

Thanks in advance.

Regards,
Seetha