Hi Felipe, thanks a lot for looking into this!
> very fine region inside the circle, I assume this is what you're trying to > avoid, right? Exactly. The problem is that I'll need a *very* fine mesh at the boundary; if extended into the circle, the number of degrees of freedom in the FEM application would be prohibitively large. > I played around a bit after adding the > "Mesh.CharacteristicLengthExtendFromBoundary= 0;" So did I, and I've got a better idea now of where my problems come from. Try for example z = 0; lcar = 0.2; lcar_fine = lcar / 100.0; width = 0.01; and you'll see the funny behavior that I see: The coarsest elements are refined in a weird way around the boundaries (see attachment). When increasing the width of the boundary region, the mesh gets back to sanity. Hm... --Nico On Fri, Dec 28, 2012 at 1:20 AM, F. A. Portela <[email protected]> wrote: > Hi Nico, > > Without adding "Mesh.CharacteristicLengthExtendFromBoundary= 0", I tried to > mesh a quarter of the circle at a time and noticed that the refinement near > the centre increases as more quarters are meshed, to the extent of having a > very fine region inside the circle, I assume this is what you're trying to > avoid, right? > > I played around a bit after adding the > "Mesh.CharacteristicLengthExtendFromBoundary= 0;" line, and the quality did > seem to deteriorate. So what I tried was to increase change line 43, > specifically I tried setting "Field[4].DistMax = 15 * width;". This makes > the transition between "lcar_fine" and "lcar" smoother and the result seems > a bit better (not sure if it's what you're looking for though). > > Another solution could be to set the characteristic lengths of > "tp2,tp3,tp4,tp5" to "lcar_fine" but this seems to give the same result as > the Attractor-Threshold method... > > Regards, > Felipe > > > -- > Felipe Alves Portela > MSc student in Aerospace Eng. at TU Delft > http://www.linkedin.com/in/felipealvesportela > > > On 26 December 2012 14:02, Nico Schlömer <[email protected]> wrote: >> >> > Mesh.CharacteristicLengthExtendFromBoundary= 0; >> >> This is producing the weiiirdest elements by taking a very coarse mesh >> and then basically adding extra nodes only on specific edges of the >> that mesh. The resulting elemens would be very bad quality. >> >> --Nico >> >> >> >> On Mon, Dec 24, 2012 at 5:38 PM, F. A. Portela >> <[email protected]> wrote: >> > Hi Nico, >> > >> > Try adding the following line to your .geo and see if it helps: >> > >> > Mesh.CharacteristicLengthExtendFromBoundary= 0; >> > >> > Merry xmas, >> > Felipe >> > >> > >> > -- >> > Felipe Alves Portela >> > MSc student in Aerospace Eng. at TU Delft >> > http://www.linkedin.com/in/felipealvesportela >> > >> > >> > On 21 December 2012 15:04, Nico Schlömer <[email protected]> >> > wrote: >> >> >> >> Hi, >> >> >> >> things are working pretty much okay with the mesh refinement along the >> >> boundary; there's thing however which I wasn't able to resolve by >> >> myself. >> >> When I refine a mesh in the vicinity of the boundary of a circle, the >> >> entire circle gets refined. The lcar statement for the center point of >> >> the circle doesn't seem to be accounted for. >> >> I attached a minimal script to highlight what's going wrong (remove >> >> the last line for meshing without any refinement). >> >> Is there a canonical way to deal with this? >> >> >> >> Cheers, >> >> Nico >> >> >> >> On Thu, Dec 20, 2012 at 12:49 AM, Nico Schlömer >> >> <[email protected]> wrote: >> >> > This is *exactly* what I needed. Thanks for the hint! >> >> > >> >> > On Thu, Dec 20, 2012 at 12:10 AM, F. A. Portela >> >> > <[email protected]> wrote: >> >> >> Hi Nico, >> >> >> >> >> >> Have you tried using the Attractor and Threshold fields? If not, you >> >> >> might >> >> >> want to have a look at Tutorial 10. >> >> >> >> >> >> The MathEval field might also be helpful, depending on the domain >> >> >> geometry >> >> >> (also used in Tutorial 10. >> >> >> >> >> >> Good luck. >> >> >> >> >> >> Cheers, >> >> >> Felipe >> >> >> >> >> >> >> >> >> -- >> >> >> Felipe Alves Portela >> >> >> MSc student in Aerospace Eng. at TU Delft >> >> >> http://www.linkedin.com/in/felipealvesportela >> >> >> >> >> >> >> >> >> >> >> >> On 19 December 2012 15:41, Nico Schlömer <[email protected]> >> >> >> wrote: >> >> >>> >> >> >>> Hi, >> >> >>> >> >> >>> I have a PDE the solution of which is known to have a steep >> >> >>> gradient >> >> >>> close to the boundary of the domain, and to be well behaved inside >> >> >>> the >> >> >>> domain. I'd thus like to create a mesh that's fine close to the >> >> >>> boundary, and somewhat coarser inside the domain. >> >> >>> >> >> >>> What are my options with Gmsh? >> >> >>> >> >> >>> Cheers, >> >> >>> Nico >> >> >>> >> >> >>> _______________________________________________ >> >> >>> gmsh mailing list >> >> >>> [email protected] >> >> >>> http://www.geuz.org/mailman/listinfo/gmsh >> >> >> >> >> >> >> > >> > > >
<<attachment: boundary.png>>
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