[Getdp] Timestepping rotating geometries

[Christophe Geuzaine]

Kristof Geldhof wrote:
> Hello,
> 
> I am trying to calculate the magnetic field patterns in a rotating 
> switched reluctance motor. My first goal is to calculate phase 
> inductances for a given phase current and different rotor positions. 
> Therefore I make use of the TimeLoopTheta routine. At each time step the 
> rotor (mesh) is being rotated over a fixed angle, the airgap is being 
> remeshed, and a static (linear) finite element calculation is made. The 
> data I'm interested in is then written into a file by calling the 
> 'PostOperation' part (see code below).
> 
> I have following problems:
> 
> 1. If I call the PostOperation part directly from the TimeLoopTheta 
> routine I get an error 'incompatible time' at the second time step. The 
> error does not occur when I perform the postprocessing after the 
> calculation using the resolution file.

I didn't code the MovingBand/ChangeOfCoordinate stuff, so I'm not sure 
why this does not work. I'm CC:ing Johan.

> 2. Calling the PostOperation part from the TimeLoopTheta routine I get a 
> series of views in the gmsh user interface. These views correctly 
> respresent the different rotor positions and magnetic flux patterns. 
> However, combining these views by clicking 'combine - Time steps - by 
> view name' does not work properly: it seems as if the rotor mesh is not 
> being rotated when clicking through the different time steps.

Combine->Time steps is designed to work *only* when the views are based 
on the same mesh, since in Gmsh a view is always associated with a 
single mesh. If you have more than one mesh, you need more than one 
view. (In your case you were "unlucky" because the number of elements is 
the same in the two views, so that Gmsh did not give you an error, even 
though the meshes were different).

See the FAQ (and gmsh/demos/anim.script) for more info on how to animate 
  and save animations with multiple views.

> 3. Trying to create timestepping views by performing the PostOperation 
> after the calculation (using the resolution file) doesn't work either.

Cf. above. Johan?

> 
> How do I solve these problems?
> 
> I also noticed a few small bugs in the Gmsh version I use (Gmsh 1.60.1 
> under Suse Linux 9.2). First of all, suppose there are two different 
> views open (for instance 'az' and 'one') and I want to change properties 
> of the second view ('one)'. After clicking 'apply' in the view options 
> window the views both get the same name 'one'...

That's probably because you have defined some links between the 
post-processing views. Make sure that View Links is set to "None" in 
Tools->Options->Post-processing.

> 
> Another strange thing is that when I load postprocessing views the 
> original geometry disappears, so I have to reload it again every time. 
> Is there some option that can be set to prevent the original geometry 
> from disappearing?
> 

Use "File->Merge" instead of "File->Open".

Christophe

-- 
Christophe Geuzaine
Applied and Computational Mathematics, Caltech
geuzaine at acm.caltech.edu - http://geuz.org