[Getdp] Coupling with other codes || PETSc

Christophe Geuzaine cag32 at case.edu
Sat May 13 23:28:11 CEST 2006

Kubicek Bernhard wrote:
> Hello!
> First of all, I would like to thank you for getDP, which seems to be a 
> really nice tool, and especially for providing it as free software. This 
> is simply great!
> A colleague of mine and me are working on a project wherein we want to 
> simulate a multiphysics problem involving numerical electromagnetism and 
> CFD. As far as I have concluded from the mailing list, getDP has no 
> Navier-Stokes solver yet, and therefore we want to couple getDP with an 
> external CFD code (FLUENT, in our case, which sadly seems not to have a 
> electromagnetic solver apart from the unaffordable ANSYS-MPCCI combination).
> As we have a transient problem, this would mean to first calculate a 
> time step with the CFD code, and then pass some relevant data to getDP, 
> which after doing its time step returns some data for the next CFD time 
> step.
> We are not 100% sure if we can calculate something useful this way, but 
> for small step sizes we hope to be lucky.
> However my first question concerns the passing of a scalar field to 
> getdp, i.E. a known temperature field.
> This field needs to be used to calculate the conductivity for each 
> volume element. InterpolationLinear seems to not suitable for functions 
> with 3 parameters.
> Is there some way of defining a field using a linear array and the 
> number of the momentary volume element?
> Maybe something similar to this fantasy-code:
> TemperatureField={0,0,0.1,0.2, .... } // for all finite volumes
> T[]=Temperature[$NrMomentaryVolume]

I think some of my colleagues in Liege do that kind of thing on a
regular basis: I've CCed them to this reply. (Patrick?)

If you use the same mesh in both codes you could simply write a .res
file containing the temperatures (and define the corresponding function
space in your .pro file). If the meshes are different, what I would
probably do is to add a new routine in getdp to read a post-processing
file (e.g. in Gmsh format) and use an octree to locate the data.

> The second question is about the state of the PETSc implementation. In 
> an not so long ago post you state that PETSc is working, but only on a 
> single cpu. As a parallel solver could be very useful to us, it would be 
> great to have an rough idea in how many months this might be ready for, 
> well, lets call it "field"-testing.

I'm not sure if getdp in its current incarnation will ever see a "real" 
parallel version: it's basically a matter of people interested in that 
stuff coding it up... (The problem is that it's not trivial to do this 
right, so that the parallelization is both efficient and "general". 
Maybe we'll have to wait for the next complete rewrite of the code.)

> Apart from this questions, I have an half finished informal introduction 
> to the weak form, which only consists of a few pages in latex, written 
> for those who hesitate to read Bossavit. If you are interested in this, 
> and want to read/comment it before maybe spreading it to other people, I 
> could finish writing it up within the next two weeks. 
> Although, I have to admit it might not reach your mathematical standards.

That would be great: you could post it to the mailing list and/or the wiki.


> Thank you very much,
> and greetings from cloudy Vienna,
> Bernhard Kubicek
> freelancer for arsenal vienna, ARC /PhD student Vienna University of 
> Technology
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Christophe Geuzaine
Assistant Professor, Case Western Reserve University, Mathematics

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