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Trouble deciding how to integrate a PDE Rate Topic: -----

#1 Schrödinger's hat 


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Psychic Sexpert
Couldn't quite figure out whether to put this in Physics, Calculus, Applied Mathematics, Computer Science, or Engineering :/

I'm trying to come up with a good scheme for integrating something similar to a thin beam equation:
Something along the lines of:
 A\frac{d^4y}{dx^4}+\text{Possibly other x derivatives}=q(x) + B\frac{d^2y}{dt^2}

But unfortunately comp-phys is but a hazy memory.

I can remember/find notes on enough to do similar things which are first order in time with finite difference methods.
Would the obvious thing of adding degrees of freedom to make:
v = \frac{dy}{dt}
\frac{d}{dt} \left[\begin{array}{c} v\\y \end{array}\right] = \left[\begin{array}{c}\frac{1}{B}(A\frac{d^4y}{dx^4} - q(x))\\v\end{array}\right]

Then applying the same methods be an effective approach? Or would it be horribly unstable?
Is there an out-of-the-box method somewhere that I'm completely missing?

This post has been edited by Schrödinger's hat: 30 September 2011 - 12:41 PM

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#2 Schrödinger's hat 


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Psychic Sexpert

View PostSchrödinger, on 30 September 2011 - 12:30 PM, said:

Then applying the same methods be an effective approach? Or would it be horribly unstable?


In case anyone else cares/comes here looking for an answer to the same question, this seems to work quite well.
The resulting system was horribly unstable with Euler method, but anything backwards-time or mixed seemed to work remarkably well.

I suppose I won't know for sure until it's compared to some data.

If anyone is watching/curious I can elaborate upon request, as there seems to be a bit of a jump in the learning curve (for what I can find online at least).
I don't believe in free will, but I choose to pretend it exists. If I'm helpful press the green button--->
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#3 khaled 


Meson
Take a look at these references:

Solution using separation of variables

Wilmott

PDE Integration with Physics Model

Scientific Notes on PDEs

PDE Integration using Discretization

Wolfram Notes on Numerical Solutions to PDE

PDE as a Linear System

PDE and Relaxation Methods

.. good luck,
Everything is a graph

twitter: @khaledkhunaifer, Blog: KhaledKhunaifer:Blog
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