Plotting fieldlines; vector plots Log Out | Topics | Search
Moderators | Register | Edit Profile

FlexPDE User's Forum » User Postings » Plotting fieldlines; vector plots « Previous Next »

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

Sabine Blatt (sblatt)
Member
Username: sblatt

Post Number: 5
Registered: 09-2005
Posted on Thursday, June 01, 2006 - 09:05 am:   

Hi there

I ran into a problem trying to plot the fieldlines of a 2d setup with bar electrodes. If I simulate a basic cell with two half electrodes using the formalism of the sample "fieldmap.pde" to calculate the fieldlines, the result looks more or less convincing (see attached file "fieldlines1.pde"). If I double the simulated area, i.e. include another electrode in between the outer ones, the fieldlines no longer follow the direction of the electric field (see attached file "fieldlines2.pde").
Does anybody know the reason for this? How do I have to change my script to get the right results?

And another question: Is there an option to set the scale of a vector plot? Sometimes the maximum is so high, anytihng else is just pink arrows and I hardly see any differences...

I would appreciate your ideas!
Chears
Sabine
application/octet-stream
fieldlines1.pde (2.5 k)

application/octet-stream
fieldlines2.pde (2.8 k)
Top of pagePrevious messageNext messageBottom of page Link to this message

Sabine Blatt (sblatt)
Member
Username: sblatt

Post Number: 6
Registered: 09-2005
Posted on Monday, June 19, 2006 - 10:08 am:   

support@pdesolutions.com wrote:
I suspect that the problem has to do with the boundary conditions on the adjoint equation (Q).

In principle, the boundary conditions for the adjoint equation must be the adjoint of the conditions on the potential. If V has a constant value, Q must have a Natura()=0. If V has a Natural()=0, Q must have a constant value. Usually this is taken care of by using the Natural(Q)=Tangential(Grad(V)). But this will not work if the boundary is internal to the problem (material on both sides). In that case, the Natural is a surface source, and is not appropriate.



If your embedded plates are represented by actual material, then you should exclude the interiors of the plates and use a Natural(Q)=0 BC on the plate outline.



Check that the left and right side BCs on Q conform to the principles above.



We usually recommend that the region 1 boundary be the outermost system boundary, and all boundary conditions be placed on this boundary. This eliminates confusion about which boundaries have been assigned, and whether duplicate BC;s are applied.
Top of pagePrevious messageNext messageBottom of page Link to this message

Sabine Blatt (sblatt)
Member
Username: sblatt

Post Number: 7
Registered: 09-2005
Posted on Monday, June 19, 2006 - 10:13 am:   

Still having trouble...

I’m afraid I don’t see how to properly define the boundaries in my specific problem.

1. I understand that natural(q)=tangential(grad(V)) doesn’t work on internal boundaries. But I still need to use it on the outer boundaries of region 1, or I won’t get a non-trivial solution at all. But this should not affect the internal boundaries which I define later, or does it?

On all the internal boundaries I tried to use explicitly the adjoint BCs for q and V (“ur” in my case) and to avoid duplicate BCs. (see attached modified script

2.8 K
fieldlines1.pde
""
)

Still the solution looks exactly the same and does not represent the physical field lines. ???

2. I don’t see how it would be possible to change region 1 in a way that I can place all BCs on the outer boundaries. I am both interested in the field distribution above and below the electrodes… ???

3. Once again, is there a way to change the colour code in a vector plot, i.e. set the maximum value?


Best wishes

Sabine Blatt

Top of pagePrevious messageNext messageBottom of page Link to this message

Sabine Blatt (sblatt)
Member
Username: sblatt

Post Number: 8
Registered: 09-2005
Posted on Monday, June 19, 2006 - 10:22 am:   

By some reason I can't upload the modified script properly. I still hope that someone can help me out, maybe based on the script "fieldlines1.pde" uploaded on june the 1st...

Thanks
Sabine

Add Your Message Here
Post:
Username: Posting Information:
This is a private posting area. Only registered users and moderators may post messages here.
Password:
Options: Enable HTML code in message
Automatically activate URLs in message
Action:

Topics | Last Day | Last Week | Tree View | Search | Help/Instructions | Program Credits Administration