[FLASH-USERS] Some questions about the new Flash.

[Norbert Flocke]

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