[gdhamale]

Hi there,
I am learning to write a UDF for plasma torch simulation (DC arc). Pl help me to understand how to write udf to solve coupled equations (attached) for my computational domain

J (current density) is known to us and defined via DEFINE_PROFILE macro (boundary condition given at the surface of a cathode) as below:
#include "udf.h"
double Rc 0.0002 /* Arc cut radius in meter*/
DEFINE_PROFILE(Current_den,t,i)
{
face_t f;
double x[ND_ND],J0,b;
begin_f_loop(f,t)
{
F_PROFILE(f,t,i)=0.;
F_CENTROID(x,f,t);
J0 = 5.7e8;
b = 2935;
if(x[1]<= Rc) F_PROFILE(f,t,i) = J0*exp(-b*x[1]);
}
end_f_loop(f,t)
}

[vinerm]

Your query is not very clear. As far as solving of an equation is conserved, then you have to enable an equation for a scalar. If you wish to use inbuilt MHD model for your application, then equation is already being solved, though with certain assumptions.

As far as the UDF is concerned, it will return a value and apply that value to whichever variable you hook it. If you hook it for current density, then it will be taken as current density. If you hook it for potential, then it will be used as potential.

[gdhamale]

Thank you for your response.
Yes, I need to enable the scalar equation (for vector and scalar potential – total 3 equations in 2D) which I have mentioned in the attached image. Could you pl explain me how to express these equations using DEFINE_SCALAR macro?

Thanks a lot!

[vinerm]

I'd suggest you to have a look at inbuilt MHD module.

https://www.afs.enea.it/project/nept...d/main_pre.htm

If you want to use your own equations, then you just need to enable scalars under User-Defined > Scalars. This is done via GUI not via a UDF. However, UDF might be required if you want to specify something special, such as, a constitutive relation or boundary condition.

[shawaditya]

Hello, I am doing a similar simulation in plasma and was wondering if you were able to solve the maxwell udf issue. I'd be extremely delighted if you could help me out

Thanks

[mm.abdollahzadeh]

If you had any success with the plasma torch model can you share a case here?
I have developed a code for that but I am facing problem with converging temperature

[sixgod]

Originally Posted by shawaditya

Hello, I am doing a similar simulation in plasma and was wondering if you were able to solve the maxwell udf issue. I'd be extremely delighted if you could help me out

Thanks

Excuse me, have you solved it now? I have the same problem.