Can you put together the simplest script possible that demonstrates the problem and I'll try and debug it? Thanks.
On Thu, May 6, 2010 at 2:01 PM, Eduard Manley <[email protected]> wrote: > Thanks for your reply. > > I probably found the reason of the problem. > > As said before I'm trying to solve an eq of this type: > > A(d phi/d t) = div (D grad phi) + q > > where A and D are costant coefficient and q is a spatially varying heat > source. > > The problem is in how I create the cylindrical 1D mesh (origin of the mesh > is not in 0.). > > It doesn't matter if the discretization is logarithmic or uniform but how I > declare it: > > (using a uniform spacing:) > > ** mesh = CylindricalGrid1D(dx=dr, nx=(len(DR))) + (r_int,) ** > SHOULD BE EQUAL TO: > > ** mesh = CylindricalGrid1D(dx=DR) + (r_int,) ** > > [dr = 5e-04, nr=58, r_int=0.00125, DR is a list which contains the various > dx(58 elements of value dr for uniform grid)] > > BUT It is NOT. > > The mesh (cell centers, facecenters) is ok but the results are NOT. > The results are right only if I create the mesh using dx=dr and nx=.. . > And this is why before I thought the problem was the logaritmic > discretization (must use DR=[...]). > > As said before with Cylindrical 2D mesh results are instead correct. > Is this a bug? > >> Date: Thu, 6 May 2010 11:11:10 -0400 >> From: [email protected] >> To: [email protected] >> Subject: Re: Problem in solving Poisson equation with 1D Cylindrical mesh >> >> >> Edward, This may be to do with having a very small volume (or area or >> line or point) for the inner most element of the domain. It should be >> the same whether one is using a 1D or 2D mesh. Since you are getting >> differences in the 1D and 2D case, it should be relatively easy to >> debug and figure out what's going on It could also be that the >> boundary condition on the inner boundary as zero area and this is >> causing issues. Try shifting the grid by a small value away from the >> zero point and see if things are improved. I have always had this >> issue with cylindrical grids and have never really had a satisfactory >> solution (other than shifting away from the zero point). If you >> discover a better way to handle this, let me know. Cheers. >> >> >> If you can't debug it, then send me the most minimalist scripts that >> show the issue and I'll give it a shot. >> >> On Wed, May 5, 2010 at 9:53 PM, Eduard Manley <[email protected]> >> wrote: >> > Problem partially solved: >> > >> > I'm using a logarithmic discretization (first dr= 5e-04 and next >> > dr increasing as 1.05)(with internal radius= 0.00125, external >> > radius=0.03) >> > and, >> > for some unknown reason this create problems and wrong result with >> > cylindrical 1D mesh. I tried using a uniform discretization (dr=5e-04 >> > nx=58) >> > and now the result is correct. >> > >> > However I need to use the logarithmic discr. so after some hours of >> > sleep >> > I'll think about the reason..... >> > >> > ________________________________ >> > Hotmail: Trusted email with powerful SPAM protection. Sign up now. >> >> >> >> -- >> Daniel Wheeler >> >> > > ________________________________ > Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. Sign up now. -- Daniel Wheeler
