- #1
jimjam1
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I'm stuck on a seemingly simple 2D electrostatics problem. The problem is as follows:
A parabolic interface ($$x(y)=cy^2$$) separates two regions of different conductivities, with a uniform electric field at infinity aligned with the x-axis.
I write the Laplace operator in parabolic coordinates, where $$x=\frac{c(u^2-v^2)}{2}$$ and $$y=cuv$$ as
$$\nabla^{2} \phi(u,v)=\frac{1}{c^2(u^2+v^2)}\left(\phi_{uu}+\phi_{vv}\right)=0$$
which, using separation of variables, gives solutions of the form
(1): $$\phi(u,v)=(A_{0}u+B_{0})(C_{0}v+D_{0})+\sum^{\infty}_{n=1}(A_{n}e^{knu}+B_{n}e^{-knu})(C_{n}\textrm{cos}(knv)+D_{n}\textrm{sin}(knv))$$.
Now, at infinity (where the electric-field is uniform), the potential is $$\phi=-E_{0}x=-E_{0}\frac{c(u^2-v^2)}{2}$$.
The problem I have is that none of the solutions in (1) admit this form for the potential... Please can someone help?
A parabolic interface ($$x(y)=cy^2$$) separates two regions of different conductivities, with a uniform electric field at infinity aligned with the x-axis.
I write the Laplace operator in parabolic coordinates, where $$x=\frac{c(u^2-v^2)}{2}$$ and $$y=cuv$$ as
$$\nabla^{2} \phi(u,v)=\frac{1}{c^2(u^2+v^2)}\left(\phi_{uu}+\phi_{vv}\right)=0$$
which, using separation of variables, gives solutions of the form
(1): $$\phi(u,v)=(A_{0}u+B_{0})(C_{0}v+D_{0})+\sum^{\infty}_{n=1}(A_{n}e^{knu}+B_{n}e^{-knu})(C_{n}\textrm{cos}(knv)+D_{n}\textrm{sin}(knv))$$.
Now, at infinity (where the electric-field is uniform), the potential is $$\phi=-E_{0}x=-E_{0}\frac{c(u^2-v^2)}{2}$$.
The problem I have is that none of the solutions in (1) admit this form for the potential... Please can someone help?