[Gmsh] boolean with surface loop

[Christophe Geuzaine]

> On 19 Nov 2018, at 18:18, Christian Kluge <ckluge at gfz-potsdam.de> wrote:
> 
> Dear Christophe,
> 
> thank you very much for your help. We were able to calculate the difference between the cylinder and the fracture and to automate the process. The "BooleanDifference" operation applied to the cylinder and fracture, results in partially very small element sizes along the fracture side (see attached figure). This causes an incomplete cylinder (upper left) or too fine refinements (cylinder bottom). 
> 
> Is there a possibility to refine the mesh of the cylinder locally? 

Sure. You can use all the usual ways to set mesh sizes: on points, using fields, etc.

To set a target mesh size on the control points of the cylinder, you could e.g. do (if the cylinder is Volume 1):

Characteristic Length{ PointsOf{ Volume{1}; } } = 0.1;

Christophe

> 
> Thank you very much.
> 
> All the best,
> Christian
> 
> 
> 
> -----Ursprüngliche Nachricht-----
> Von: Christophe Geuzaine [mailto:cgeuzaine at uliege.be] 
> Gesendet: Freitag, 16. November 2018 22:58
> An: Guido Blöcher <bloech at gfz-potsdam.de>
> Cc: gmsh at geuz.org; Christian Kluge <ckluge at gfz-potsdam.de>
> Betreff: Re: [Gmsh] boolean with surface loop
> 
> 
> 
>> On 16 Nov 2018, at 16:43, Guido Blöcher <bloech at gfz-potsdam.de> wrote:
>> 
>> Dear Christoph,
>> 
>> 
>> 
>> We try to mesh a three dimensional fracture embedded in a cylindrically shaped rock volume.
>> 
>> We can mesh the fracture and the cylinder separately but for later use as input for  a numerical simulation, we have to subtract or intersect the two volumes.
>> 
>> 
>> 
>> Unfortunately, gmsh provides an error message regarding our surface loop.
>> 
>> Gmsh complains that our surface loop is not a valid openCascade entity.
>> 
> 
> Indeed: in your script you SetFactory("OpenCASCADE") after having created the first volume - which was thus created with the default "Built-In" CAD kernel.
> 
> Here's a working script:
> 
> <16x32.png><16x32.geo>

— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine

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