Forum Message

 

 

We have moved the forum to https://forum.ngsolve.org . This is an archived version of the topics until 05/05/23. All the topics were moved to the new forum and conversations can be continued there. This forum is just kept as legacy to not invalidate old links. If you want to continue a conversation just look for the topic in the new forum.

Notice

The forum is in read only mode.

BH curve

More
1 year 1 month ago #4620 by lahoussaine
BH curve was created by lahoussaine
Good morning community;
is there a way to implment bh curve using ngsolve : 
i do somthing like 
def nuf(u):
     return Norm(grad(u))
nu=CoefficientFunction(nuf)
a+=nu*grad(u)*grad(v)*dx
but always i got nan values !
any tricks ? 
More
1 year 1 month ago #4621 by mrambausek
Replied by mrambausek on topic BH curve
Dear Lahoussaine,

what is the actual model you want to implement?
"Norm(grad(u))" does not seem to a suitable model in first place, as it leads to a singular matrix for grad(u) = 0.

Best,
Matthias
More
1 year 1 month ago #4625 by lahoussaine
Replied by lahoussaine on topic BH curve
I want something like
1/(B**3+B**2+B )
or :
3.8*exp(2.17*B*B)+396.2

I ve tried those expression but it gives always NAN;

Thankes for your reply
More
1 year 1 month ago #4626 by mrambausek
Replied by mrambausek on topic BH curve
TBH, I have never seen any magnetic model like that (which might not mean a lot...)

I can't see how the first one could give something reasonable for B=0.

Before using a nonlinear model, did you have a working version for a constant "nu"?

I fear, we need much more information to be able to help you.


Best
More
1 year 1 month ago #4627 by lahoussaine
Replied by lahoussaine on topic BH curve
def nuf(u):
IfPos(2.28-B,(1/(-0.003995*B**3+0.005956*B**2+0.00646*B + 0.001925)), ((1902.211*B-4266.42343)/0.016694669))

Here is my formule, but it doesn't work
The problem is whenever i put norm(B) it returns NAN
even if the formula is well defined( 1/(B**2+1) for example )


Thank you and Sorry to not be claire
More
1 year 1 month ago #4628 by mrambausek
Replied by mrambausek on topic BH curve
Unfortunately, I still miss some information: how is "B" defined?
Where does the "Norm" enter in "1/(B**2 + 1)
Which command did you use for assembly? Where exactly do you get NaN? Already in the matrix or only after solving, i.e. in the solution?

Could you maybe post a complete minimal example that reproduces your problem?
Time to create page: 0.107 seconds