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Any ideas?

Hi

a few comments:
you do not really need to simulate the aluminium electrodes in your case, you can consider the upper and lower faces of your water bed as electrodes with a fixed potential, or add a thin conductive layer, but even that is not really required, as aluminium is so much more conductive as the middle dielectric that you will not get any real gradients in the aluminium layer

Then the results look quite OK w.r.t. your material values, with your cell membrane conducting much more than the surrounding, you get hardly any current flow inside the cell. For a better rendering, I would propose that you use a 2D plot with a "surface plot" pointing to the "Data set cut plane" and add a "contour" plot with uniform colouring

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Good luck
Ivar

Hi Ivar,

Thank you very much for your quick response, sorry not answer before I had left home.

You were right, the conductivity of extracellular medium was badly defined, is 1.5 [S / m] approx, the membrane can be approximated by 1e-7 [S / m] and inside the cell 0.6 [S / m ]. Following your instructions I removed the aluminum plates, yet I think the result is not correct.

What I get is about opposing electric field lines (attached pictures). Actually, I don't know what I am doing wrong, I have done a simulation with the same parameters in axial symmetry and the result was correct (attached photo). Do you have any idea about why this happens?

Would I like to ask you a question axial symmetry axis can rotate, 45 degrees for example?

Is it possible to represent the angle theta with a special command or need to calculate the atan?

Thank in advance,
Regards,

Michael.

Hi

I'm not sure why, but as you don not use any titles I'm not sure you are plotting the same values on the same region. Is it on a "data set cut plane" ? or on a slice of a 3D plot with volume arrows ?

then your 2D colour plot is strange (on the "good" one, it looks like a "r" and not like a "z" component or a norm value)

for the axis of a 2D-axi plot it's always, by design in COMSOL, "r" along the 2D x direction and z along the usual 2D y axis with the corresponding variable name changes (u,w for solid, ...)

I'm not fully sure I understand what you mean about a 45° inclined axis case

The theta or ("phi" for COMSOL in circular) angular value is there too, so you might get a atan() calculation (turn on the equations view (sub-nodes) and take a look therein. When you use coordinate systems you have the sys2.r and sys2.phi (might be identifier 3 or 4 all depends on how many coordinate systems you have defined)

If you are looking for the spherical theta = atan(z/r) you need to define a "Model Definition Variable" in this way
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Good luck
Ivar

Thanks Ivar,

Your answer has been helpful to me, now I managed to correctly represent the electric field is now symmetrical as I expected. But the current density is not as uniform as in the case of axial symmetry. I attached the picture that I get if I use a slice instead of a 2D surface. When, I represent 2D surface I get a result that seems to be wrong.

I am attaching the photo of the axial symmetry with axis labels and the model. Could you tell me please if I´m doing something wrong in the model? I think that the main problem is with the 3D post processing, I´m relative new user in Comsol only 4 month and I had never used the 3D model in Comsol, all I have been done had been models in 2D axial or 2D now, I am trying to jump to 3D model. I really appreciate your help

Best regards,

Michael.

Hi

I rather suspect that your mesh is not the same in the two cases, try to plot the variable "h" in 2D-axi and 3D cut plane, or add in the superposition of the mesh grid on your cut plane view.

Often one need a very fine mesh which translates to huge models in 3D

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Good luck
Ivar