[FLASH-USERS] Some questions about the new Flash.
Norbert Flocke
flocke at flash.uchicago.edu
Wed Sep 26 11:26:55 EDT 2012
Hi Giovanny,
Here is the answer to one of you questions:
the simulation run ok~E but for calculate the force I need to find
dR*dZ, so I call dvol from domain and divide over 2*pi*x(i). The
result is exactly 2E28 when I perform the sum. So, this is ok.
(Nevertheless, I don't understand why I must to divide over 2*pi*x(i)
and no only over pi*x(i)?~E the cylindrical volume in 2d is
pi*dR^2*dZ, no?)
The dvol in cylindrical coordinates is calculated as a difference between
two cell boundary radii: r and R. So we have:
dvol = pi * (R^2 - r^2) * dZ
But the radial location of the center of your volume element is x(i), and
it is halfway of the cell radial distance dR from both r and R. So:
r = x(i) - dR/2
R = x(i) + dR/2
Then we have:
dvol = pi * ([x(i) + dR/2]^2 - [x(i) - dR/2]^2) * dZ
= pi * (x(i)^2 + x(i)dR + dR^2/4 - x(i)^2 + x(i)dR - dR^2/4) * dZ
= pi * (x(i)dR + x(i)dR) * dZ
= 2pi*x(i)*dR*dZ
Hope this helps you.
Best Regards,
Norbert
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