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Eugene B. Postnikov (postnikov)
New member
Username: postnikov

Post Number: 2
Registered: 06-2004
Posted on Friday, June 02, 2006 - 08:10 am:   

Hello,
I've found the following trouble: I try to solve
the system of two equations (see .pde file in the attachment) but FlexPDE5 shows an exponetial growth instead of a solution with two maxima (But FlexPDE4 solves this probem correctly, see .gif file in the attachment). If I use 1D geometry, the error is the same.
Could you help?
Thank you in advance,
Eugene B. PostnikovMOrlet02_1196.gif

0.7 K
MOrlet.pde
""
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Robert G. Nelson (rgnelson)
Moderator
Username: rgnelson

Post Number: 622
Registered: 06-2003
Posted on Friday, June 02, 2006 - 02:40 pm:   

Your script does not seem to be downloadable.
Please send it directly to
support@pdesolutions.com
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Robert G. Nelson (rgnelson)
Moderator
Username: rgnelson

Post Number: 624
Registered: 06-2003
Posted on Saturday, June 03, 2006 - 11:31 pm:   

It appears that changes made in the symbolic processing of equations to support moving meshes in version 5 have introduced an error in symbolic handling of equation coefficients that are explicitly time dependent.

It is not sufficient to merely hide the time in a parameter definition, because definitions are expanded during processing.

I will fix this in the next maintenance release, but for now there is a workaround you can use:
1) define a GLOBAL VARIABLE, for example, K
2) give the GLOBAL VARIABLE the EQUATION K: K=t
3) use K as the diffusivity in your existing equations.

This process hides the time dependence of K from the equation analyzer.

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