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Re: Force Field [message #45494 is a reply to message #45491]

Tue, 13 September 2005 19:13

Kenneth P. Bowman
Messages: 585
Registered: May 2000

Senior Member

In article <1126634205.227520.96190@f14g2000cwb.googlegroups.com>,
"Andres" <panblosky@gmail.com> wrote:

> Hi all,
>
> I have a potential field on a grid (it has periodic boundary
> conditions), and I want to calculate the acceleration (force field) of
> this, i.e., f=-grad(potential), I need the gradient of the potential .
> I wrote a procedure, but it has to many for loops in it. Does any body
> know a fast and smart way to do this?
> Thanks!!
>
> Andres

Assuming that you are happy with first-order, centered differences, you
want something like this

grad_x = (SHIFT(phi, -1, 0) - SHIFT(phi, 1, 0))/(2.0*dx)
grad_y = (SHIFT(phi, 0, -1) - SHIFT(phi, 0, 1))/(2.0*dy)

where phi is the potential It think this handles the periodic boundary
conditions properly, but check to make sure.

Cheers, Ken Bowman

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[Message index]

		Re: Force Field By: panblosky on Wed, 14 September 2005 04:03
		Re: Force Field By: Kenneth P. Bowman on Tue, 13 September 2005 19:13
		Re: Force Field By: David Fanning on Tue, 13 September 2005 11:22

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