Re: CylindricalGrid1D mesh volumes
On Fri, Jan 17, 2020 at 5:31 AM Pavel Aleynikov wrote: > > sort of ratio so the absolute value of the volume won't matter. > Unless you have a source with a defined integral absolute value. But I agree > that in general "theta = 1" is not a problem, as long as it's clear from the > documentation. The documentation is probably not clear on this, but thanks for raising the issue. -- Daniel Wheeler ___ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
Re: CylindricalGrid1D mesh volumes
Ok. I understand. I see the logic of saving on some operations. > Argulably, these quantities should be calculated in some > sort of ratio so the absolute value of the volume won't matter. Unless you have a source with a defined integral absolute value. But I agree that in general "theta = 1" is not a problem, as long as it's clear from the documentation. -- Pavel > On 15 Jan 2020, at 17:34, Daniel Wheeler wrote: > > On Wed, Jan 15, 2020 at 4:21 AM Pavel Aleynikov > wrote: >> >> Hi, >> >> How are "mesh.cellVolumes" defined in fp.CylindricalGrid1D case? >> The surface of a circle grid is not equal pi*r^2. >> >> import fipy as fp >> L= 1.; nx = 1000 >> mesh = fp.CylindricalGrid1D(dx=L/nx, nx=nx) >> print(mesh.cellVolumes.sum()) 0.5 >> >> Why not pi? > > I'm not sure. It's an arbitrary choice though. The angle was chosen as > "1" rather than "2 * pi". The volume of an element is "theta * r * dr" > where "theta" is the > angle, "r" are the cell centers and "dr" is the cell spacing. It's > possible that by choosing "theta=1", then the "theta" can be omitted > saving an extra operation. > >> How should I integrate Variables on such a grid? >> (2*pi*Var*mesh.cellVolumes).sum()? > > Makes sense. Argulably, these quantities should be calculated in some > sort of ratio so the absolute value of the volume won't matter. > > -- > Daniel Wheeler > ___ > fipy mailing list > fipy@nist.gov > http://www.ctcms.nist.gov/fipy > [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] > ___ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
Re: CylindricalGrid1D mesh volumes
On Wed, Jan 15, 2020 at 4:21 AM Pavel Aleynikov wrote: > > Hi, > > How are "mesh.cellVolumes" defined in fp.CylindricalGrid1D case? > The surface of a circle grid is not equal pi*r^2. > > import fipy as fp > L= 1.; nx = 1000 > mesh = fp.CylindricalGrid1D(dx=L/nx, nx=nx) > print(mesh.cellVolumes.sum()) > >> 0.5 > > Why not pi? I'm not sure. It's an arbitrary choice though. The angle was chosen as "1" rather than "2 * pi". The volume of an element is "theta * r * dr" where "theta" is the angle, "r" are the cell centers and "dr" is the cell spacing. It's possible that by choosing "theta=1", then the "theta" can be omitted saving an extra operation. > How should I integrate Variables on such a grid? > (2*pi*Var*mesh.cellVolumes).sum()? Makes sense. Argulably, these quantities should be calculated in some sort of ratio so the absolute value of the volume won't matter. -- Daniel Wheeler ___ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
CylindricalGrid1D mesh volumes
Hi, How are "mesh.cellVolumes" defined in fp.CylindricalGrid1D case? The surface of a circle grid is not equal pi*r^2. import fipy as fp L= 1.; nx = 1000 mesh = fp.CylindricalGrid1D(dx=L/nx, nx=nx) print(mesh.cellVolumes.sum()) >> 0.5 Why not pi? How should I integrate Variables on such a grid? (2*pi*Var*mesh.cellVolumes).sum()? Thank you, Pavel PS. The solution of a diffusion equation on the CylindricalGrid1D seems fine, i.e. it converges to Bessel J_0 eigenvalue fairly well. PPS. I've accidentally sent this message from an unregistered email first and the cancelation link in the autoreply does not work. So, sorry if this is the duplicate. ___ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
