Question: Using toroidal in PDEchangecoords & defining inverse toroidal

Hello everybody,

i am trying to use PDEchangecoords to transform a system of differential equations from Cartesian coordinates to toroidal coordinates. However, when i use a user defined coordinate transform from toroidal to Cartesian, i don't get the initial equations. Please find attached a minimal working environment.

i would highly appreciate your hints and suggestions!

Thank you

Best regards,

F

question.mw
 

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restart; with(DEtools); addcoords(invToroidal, [xi, eta, phi], [sinh(xi)*cos(phi)/(cosh(xi)-cos(eta)), sinh(xi)*sin(phi)/(cosh(xi)-cos(eta)), sin(eta)/(cosh(xi)-cos(eta))]); PDEchangecoords(diff(f(x, y, z), z), [x, y, z], toroidal, [xi, eta, phi]); PDEchangecoords(%, [xi, eta, phi], invToroidal, [x, y, z]); print("i would expect here to get", diff(f(x, y, z), z))

"i would expect here to get", diff(f(x, y, z), z)

(1)

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