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# What is the error message NDSolve::femcbtd: all about?

Posted 9 years ago
 I'm trying to use NDSolve to solve Laplace's Equation over a particular region of 2D space. When I try to get an answer I receive an obscure error message that does not appear to be documented anywhere on the Wolfram site. NDSolve::femcbtd: A coordinate that is part of the region NDSolveFEMNumericalRegion[ImplicitRegion[<<1>>,{z,r}],{{-(102939420054182/5146971002709099),(1<<13>>2)/(5<<14>>9)},{0,<<1>>}}] could not be found in time 1.. Either specify a coordinate that is part of the region via the "TestData" option or increase the time to find such a coordinate via the option TimeConstraint. >> I cannot get NDSolve to accept either of the options "TestData" or TimeConstaint Here's the code:- R1 = 0.006; R2 = 0.015; Rm = 0.015 Sqrt[2]; Ur = 3500.; z0 := Sqrt[r^2/2 - R^2/2 + Rm^2 Log[R/r]] z1[r_] = z0 /. R -> R1; z2[r_] = z0 /. R -> R2; Off[InverseFunction::ifun]; r1 = InverseFunction[z1]; r2 = InverseFunction[z2]; \[CapitalOmega] = ImplicitRegion[{r >= r1[z] && r <= r2[z]}, {{z, -0.02, 0.02}, {r, 0, 0.05}}]; RegionPlot[\[CapitalOmega], AspectRatio -> Automatic] op = Laplacian[u[r, z], {r, z}]; \[CapitalGamma]1 = DirichletCondition[u[r, z] == Ur, r == r1[z]]; \[CapitalGamma]2 = DirichletCondition[u[r, z] == 0, r == r2[z]]; sol = NDSolve[{op == 0, \[CapitalGamma]1, \[CapitalGamma]2}, u, {r, z} \[Element] \[CapitalOmega]]; ` Can anybody shed any light on this? Donald Attachments:
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