[Gmsh] combine elements from different physicals

[Ruth Vazquez Sabariego]

Hi Nigel, 
You can just create a new physical with the 3 of them together. The original individual ones:
> Physical Surface("wake") = {ps1};
> Physical Surface("fluid") = {ps2};
> Physical Surface("pmlxy") = {ps3};

and the one containing the three of them:
> Physical Surface(“wake+fluid+pmlxy") = {ps1,ps2,ps3};

HTH,
Ruth

—
Prof. Ruth V. Sabariego
KU Leuven  
Dept. Electrical Engineering ESAT/Electa, EnergyVille
http://www.esat.kuleuven.be/electa
http://www.energyville.be

Free software: http://gmsh.info | http://getdp.info | http://onelab.info







> On 12 Feb 2017, at 16:42, Nigel Nunn <nnnunnn at gmail.com> wrote:
> 
> Hi - a solver I'm testing requires all that elements in a gmsh .msh belong to a single elementary/physical region, e.g. "fluid".  For another solver, we use different regions to help adjust mesh density ("wake", "fluid", "pml"}. For example, if we specify Physicals like this:
> 
> Physical Surface("wake") = {ps1};
> Physical Surface("fluid") = {ps2};
> Physical Surface("pmlxy") = {ps3};
> 
> then in the mesh file, we get a PhysicalNames section like this:
> 
> $PhysicalNames
> 7
> 1 1 "Wall"
> 1 2 "Slip"
> 1 3 "Inflow"
> 1 4 "Outflow"
> 2 5 "wake"
> 2 6 "fluid"
> 2 7 "pmlxy"
> $EndPhysicalNames
> 
> In the $Elements section, Physicals {5,6,7} get tags like this:
> 
> 2 2 5 530
> 2 2 6 531
> 2 2 7 532
> 
> What we want is to merge all three of these 2d ("Plane Surface") regions into a single "fluid" physical, like this:
> 
> $PhysicalNames
> 5
> 1 1 "Wall"
> 1 2 "Slip"
> 1 3 "Inflow"
> 1 4 "Outflow"
> 2 5 "fluid"
> $EndPhysicalNames
> 
> We can do this manually by replacing tags for physicals 6 and 7 with tags for physical 5; just wondering if gmsh has a command or plugin to do this?
> 
> - thanks!
> 
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