Solving electrostatic, rotationally symmetric 3D problem with conformal mapping?

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Discussion Overview

The discussion revolves around the applicability of conformal mapping techniques, typically used for solving 2D problems, to 3D axial-rotationally symmetric electrostatic problems. Participants explore the differences in solution approaches between 2D and 3D scenarios, particularly focusing on the implications of symmetry in the mathematical treatment of these problems.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests that conformal mapping, effective for 2D problems, might be applicable to 3D axial-rotationally symmetric problems, which they view as effectively 2D with additional terms in the differential equation.
  • Another participant argues that azimuthally symmetric 3D problems yield different solutions than 2D problems, indicating that the solution methods are not interchangeable and that radial solutions involve Bessel functions rather than sine/cosine functions typical of 2D rectangles.
  • A participant seeks clarification on whether complex variable methods like conformal mapping can still be utilized for the 2D aspect of the 3D problem.
  • One participant clarifies that while conformal mapping can solve 2D problems in planar boundaries, it does not apply to 3D azimuthally symmetric problems. They reference historical work by Maxwell on capacitance that approximated a 2D solution valid far from the axis, ultimately concluding that the general answer is no.

Areas of Agreement / Disagreement

Participants express disagreement regarding the applicability of conformal mapping to 3D problems, with some asserting that it cannot be used while others explore its potential for 2D aspects. There is no consensus on the matter.

Contextual Notes

The discussion highlights the limitations of applying 2D solution techniques to 3D problems, particularly in terms of the mathematical functions involved and the conditions under which certain methods may or may not be valid.

Gerenuk
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I heard that one can solve 2D problem with conformal mapping of complex numbers.
Is it possible to use this method for 3D axial-rotationally symmetric problems (which are effectively 2D with a new term in the differential equation)?
 
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Azimuthally symmetric 3D problems have different solutions than 2D ones, so solution approaches are not interchangeable. Take a cut through a cylinder including the axis--it looks like a rectangle, but radial solutions are Bessel functions. The sine/cosine solutions you'd get from solving it as a 2D rectangle are flat out wrong.
 
I know that.
I was wondering if one can still use some kind of complex variable method such as conformal mapping to treat this 2D problem.
 
To be clear on what you mean by "this" 2D problem:
Solution of 2D problem in a planar boundary like rectangle--yes
Solution of 3D azimuthally symmetric problems--no.

Actually, Weber recounts that Maxwell evaluated the capacitance of parallel plates with guard rings by approximating as a 2D conjugate-function solution valid far from the axis. The general answer is no.

Weber, Electromagnetic Fields, Vol. 1: Mapping and Fields, Wiley, 1950.
 
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