GetDP

[Christophe Geuzaine]

Samuel Kvasnica wrote:
> 
> The form of the field is almost correct, but not completely. The symetry should be
> better in my opinion.
> I think its a problem of boundary conditions in infinity.  I'd like to ask you
> following questions:
> 
> A assumed, in cylindrical coordinates x corresponds to r and y to z coordinate, x
> always >=0. Correct ?

yes

> 
> Do I have to set any constraints on axis r=0 when using cylindrical coordinates ?

yes : b_n = 0 -> a_t = 0 

-> in 2D, a = 0 will do

> 
> Z-component of vector potential A seems to be useful when displaying 2D solenoidal
> fields. But in case
> of permanent magnets, I need to use also scalar potential (Bperm=grad phi). Correct ?

why ? you can also impose the field with a vector potential... If nu =
mu^(-1) and hc is the coercitive field, one way to proceed is 

b = mu (h-hc)
h = nu b + hc
b = curl a
for all a'

=> (curl h, a') = (j, a')
=> (h, curl a') - <n x h, a'> = (j, a')
=> (nu b, curl a') + (hc, curl a') - <n x (nu b), a'> - <n x hc, a'> =
(j, a')
=> (nu curl a, curl a') + (hc, curl a') - <n x (nu curl a), a'> - <n x
hc, a'> = (j, a')

Of course the first surface term <n x (nu curl a), a> is the classical
Newmann term, while <n x hc, a> is almost always null.

> 
> What is the meaning of Spherical shell transformation ? Is it a projection of
> <Rint,Rext> on <Rint,infinity>

yes. Beware that it is a spherical transformation ! It transforms a
sperical portion of the space (your mesh is not correct for use with
this transformation...)

> to set the value of potential or induction to 0 in infinity ? What should I use in
> case of axial symetry ? I've just
> assigned induction to 0 somewhere in a distance.

You should assign the potential to zero on the outermost circular
boundary (the values of Rint and Rext must coincide with the geometrical
values of the radii of the two circles)

> 
> In your magnetostatic example MagSta_a_2D, what is the meaning of SurfaceGh0 and
> SurfaceGe0 ?
> I just noticed A is set to 0 at SurfaceGe0. How getDP recognises the symetry ? Does
> setting A to 0
> at SurfaceGe0 mean mirror symetry ? What about Gh0 ? Well, I'm really confused...

Symmetries are just well set boundary conditions... If the symmetry
implies e.g. that the normal component of b is zero (perpendicular
current), then you should set the tangential component of a (or e) to
zero. And so on: there is no trick behind symmetries...

> 
> I'd like to generate a table of B on grid. I don't understand the syntax of OnGrid
> 
> Plot[ b,   OnGrid {{-0.07,eps,0}{0.09, eps, 0}} {500}, File "b_phi.cut"] ;
> 
> Could you explain me please, what are 2 vectors following keyword 'OnGrid'
> 
> and what means {500} ?
> 

Well this has changed in the new version : check the user's guide. To
plot on a 2D grid (i.e. on a plane specified by 3 points {x1,y1,z1}
{x2,y2,z2} and {x3,y3,z3}), you shoud use

Plot[ b,   OnPlane {{x1,y1,z1}{x2,y2,z2}{x3,y3,z3}} {nbpts1, nbpts2},
File "b_phi.cut"] ;

> What is the difference between OnCut and OnGrid ?

OnCut really cuts the mesh (computes intersections)

> 
> What is the meaning of Depth keyword ?

Recursive subdivisions of elements in the postprocessing (e.g. for use
with high order reconstructions)

> 
> What means '>' in File <'>'> "string" ?

append to the file

> 
> And finally: do you have any experience with use of GID or SolidMesh in combination with getDP ?

No. Could you send me more information ?



-- 
Christophe Geuzaine

Tel: +32-(0)4-366.37.10    mailto:Christophe.Geuzaine at ulg.ac.be
Fax: +32-(0)4-366.29.10    http://www.montefiore.ulg.ac.be/~geuzaine/