Does anyone know if the poisson solver will enable the calculation of capacitance between electrodes with a cylindrical structure?
To clarify: There is an electrostatic solver in the Los Alamos Poisson-Superfish package. While it is easy enough to get E-field plots, I cannot see a way of getting the capacitance between the electrodes.
I’ve done that with a different electrostatic solver, for two conductors, one at potential zero and the other at potential U. The values of the potentials are set on the surfaces of the conductors at the stage when you specify the boundary conditions of the simulation. One can then use Electrostatic Energy=C*U^2/2=IntegralOverVolume(eps_0*E^2*dV/2) and obtain C from there. E is the electrostatic field obtained by the solver and if the solver cannot do the integral then you need to export E in a table file and perform the integration with MATLAB or a similar package.
SF7 can give the position and the components of the electric field in a grid, or between two or more points
Let us consider the provided CoaxCapacitor example, where C=60pF/m :
Note R and ER of a point shown by WSFplot somewhere between the two conductors
DZ is the pitch along the axis Z
The theorem of Gauss tells that the charge Q is related to the flux through the surface by Q=Epsilon * ER * (DZ *2*Pi*R)
As the difference of voltage between the two conductors is V then C=Q/V
hope you find this Poisson Superfish manual useful:
https://www.osti.gov/servlets/purl/10140827
Thank you to everyone who has replied. Since asking this question, I discovered the MIT FastCap program, which is downloadable as C source code. In my tests, FastCap is found to calculate capacitance with very good accuracy (essential for my purpose). I plan to publish something on this in 2020.
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