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Thread Subject:
Nonlinear equations PDE toolbox!

Subject: Nonlinear equations PDE toolbox!

From: Fermi's Liquor theory

Date: 29 Mar, 2013 19:12:05

Message: 1 of 4

Hey all,

I'm trying to solve an equation of the form del^2(u) = f(u) for a non-polynomial function f. I really can't see how to do this with the gui, which seems to only be able to solve very basic equations. I have been told that it is possible to export the scripts and define the equation manually, but really have not managed to find any examples of that being done.

I would appreciate links to documentation that explain this very much!

Cheers
x

Subject: Nonlinear equations PDE toolbox!

From: Bill Greene

Date: 30 Mar, 2013 12:12:11

Message: 2 of 4


> I'm trying to solve an equation of the form del^2(u) = f(u) for a non-polynomial function f. I really can't see how to do this with the gui, which seems to only be able to solve very basic equations. I have been told that it is possible to export the scripts and define the equation manually, but really have not managed to find any examples of that being done.
>
> I would appreciate links to documentation that explain this very much!

In fact, this equation can be solved using the pdetool GUI.

You can enter your expression for f as a string in the PDE Specification Dialog.
More details on the form of this expression can be found here:
http://www.mathworks.com/help/pde/ug/scalar-coefficients-in-string-form.html
You also have to check the "Use nonlinear solver' box in the Solve Parameters dialog
before pressing the solve button.

If you would rather solve the equation using the command line interface, an example
is here:
http://www.mathworks.com/help/pde/examples/minimal-surface-problem-on-the-unit-disk.html

Bill

Subject: Nonlinear equations PDE toolbox!

From: Fermi's Liquor theory

Date: 30 Mar, 2013 17:56:07

Message: 3 of 4

"Bill Greene" wrote in message <kj6kqr$pn2$1@newscl01ah.mathworks.com>...
>
> > I'm trying to solve an equation of the form del^2(u) = f(u) for a non-polynomial function f. I really can't see how to do this with the gui, which seems to only be able to solve very basic equations. I have been told that it is possible to export the scripts and define the equation manually, but really have not managed to find any examples of that being done.
> >
> > I would appreciate links to documentation that explain this very much!
>
> In fact, this equation can be solved using the pdetool GUI.
>
> You can enter your expression for f as a string in the PDE Specification Dialog.
> More details on the form of this expression can be found here:
> http://www.mathworks.com/help/pde/ug/scalar-coefficients-in-string-form.html
> You also have to check the "Use nonlinear solver' box in the Solve Parameters dialog
> before pressing the solve button.
>
> If you would rather solve the equation using the command line interface, an example
> is here:
> http://www.mathworks.com/help/pde/examples/minimal-surface-problem-on-the-unit-disk.html
>
> Bill




Thanks bill, this is very useful. Do you happen to know if there is a way to use pre defined functions of u? Or would I have to manually code this.

On a side note, do you know of any guides on how to edit the script generated by the gui, as it doesn't really seem to bear much resemblance to the commands you would use when manually coding the problem? (Apologies if these are trivial questions, my google searches aren't really turning out much)

Subject: Nonlinear equations PDE toolbox!

From: Fermi's Liquor theory

Date: 1 Apr, 2013 13:36:15

Message: 4 of 4

anyone else? I really want to generate the geometry, which is quite complex, using the gui and then code the equation manually. I can't seem to find a good explanation on how to edit the script generated in this way, and all the tutorials seem to be either using one or the other?

Cheers!

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