Discussion Forum

Hi

normally COMSOl will propose different variable names and solve for all (V V2 V3 ...) it's then up to you to define the common boundaries where you want to define continuity between the different "V"s

The best is to avoid similar variable multiplication and combine different physics subnodes for the different domains (when possible)

--
Good luck
Ivar

Thanks Ivar for your reply. In this model I wish to apply an electric shock (Voltage) at electrodes using the electrostatic model and observe the distribution of charge/field/potential/current density as a result of this applied voltage in the domain using the Poisson's model. How do I do this? Currently, with different variable names for Voltage in the 2 models, I dont see any response in the Poisson's model and that's when I realized that the reason could be due to different names for the voltages using the 2 models.

Thanks a lot for your help.
Deepika

Hi

But ES is "static" you would need EC to get any current flow. Then you need to check that all your physics accept the same solvers (not all phyiscs are set upfor all time, frequency domain, ... solver cases)

If you cn fully segregate, its possible to solve for some physics, then use the results as initial and continuous values for the next study

--
Good luck
Ivar

Thanks Ivar.

That makes sense to use ec and not es. The intention of this model is only to obtain a static distribution of field/potential/current density in the Poisson's model as a result of the applied voltage in the ec model. Now how do I use the results of the ec model as initial conditions for the Poisson's model?

Attached is the model with ec and Poisson's equation. I wish to see an output for u (dependent variable - Poisson's) as a result of the the applied voltage of + and - 100 V at the electrodes.

Thanks for your help.
Deepika

Do you really need multiple physics here? Electrostatics essentially solved the same Poisson's equation (when source term is non zero) or Laplace equation with zero source term. I think you will need only one physics either EC or ES.

Good luck.

Thanks Mranal...

Mranal/Ivar/Comsol community,

I understand that the es and ec models are basically use Poisson's/Laplace's equations. But what I dont understand is that with the same material properties and same geometry. I get different results for es and ec models. I am missing something.

I sincerely appreciate any help.

Attached are my ec and es models.

Thanks
Deepika

The different results are due to different equations in these modules (ES to be used in dielectric media and EC to be used in conducting media). Please refer to AC/DC module user guide page 151 (theory of electric field) which talks about choosing between these two interfaces based on external and charge relaxation time scales. The documentation is very well written, it should clear your doubts.

Good Luck.

Thanks Mranal.

Mranal,

I sincerely appreciate your help. What I fail to understand is with the ec model I get a voltage distribution between -100 and -100V which does not make sense. Whereas with the es model I get a voltage distribution between +100 and -100V which is the applied voltage at the 2 electrodes.

I did read through the documentation and I agree that it is well explained and ec seems to be the route.

But do you have any idea why I get such a result and what could it mean?

Thanks
Deepika