Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.
Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
Global constraint
Posted 3 janv. 2011, 17:16 UTC−5 Version 4.0a 1 Reply
Please login with a confirmed email address before reporting spam
Hi,
Would you please help me out? I’m working with COMSOL v4a. I want to define a global constraint for electric field norm (ec.norm) using point integration and Global equation under ge model with non-zero initial condition. But I have this error:
Attempt to evaluate negative power of zero.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.ec.normE@VDN$mod1.Vy
- Defined as: (((-conj(mod1.ec.Ey))+(-conj(mod1.ec.Ey)))*((((realdot(mod1.ec.Ex,mod1.ec.Ex)+realdot(mod1.ec.Ey,mod1.ec.Ey))+realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5)*0.5))
Failed to evaluate expression.
- Expression: d(mod1.ec.normE,mod1.Vy)
Thanks,
Gita
Would you please help me out? I’m working with COMSOL v4a. I want to define a global constraint for electric field norm (ec.norm) using point integration and Global equation under ge model with non-zero initial condition. But I have this error:
Attempt to evaluate negative power of zero.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.ec.normE@VDN$mod1.Vy
- Defined as: (((-conj(mod1.ec.Ey))+(-conj(mod1.ec.Ey)))*((((realdot(mod1.ec.Ex,mod1.ec.Ex)+realdot(mod1.ec.Ey,mod1.ec.Ey))+realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5)*0.5))
Failed to evaluate expression.
- Expression: d(mod1.ec.normE,mod1.Vy)
Thanks,
Gita
1 Reply Last Post 4 janv. 2011, 04:03 UTC−5
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
if you look at the formula:
((((realdot(mod1.ec.Ex,mod1.ec.Ex)+realdot(mod1.ec.Ey,mod1.ec.Ey))+realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5)*0.5)
realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5
then if Ex=Ey=Ez =0 this ^-0.5 gives a NaN hence the error
two ways out:
a) either you adapt Ex,Ey,Ez to avoid Ex=Ey=Ez=0, or
b) you cheat a little (might not work) and you add in the formula (under equations)
... realdot(mod1.ec.Ez,mod1.ec.Ez)+eps)^-0.5)...
But most probably you shouldavoid "nofield" by a better BC or initial value conditions
--
Good luck
Ivar
if you look at the formula:
((((realdot(mod1.ec.Ex,mod1.ec.Ex)+realdot(mod1.ec.Ey,mod1.ec.Ey))+realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5)*0.5)
realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5
then if Ex=Ey=Ez =0 this ^-0.5 gives a NaN hence the error
two ways out:
a) either you adapt Ex,Ey,Ez to avoid Ex=Ey=Ez=0, or
b) you cheat a little (might not work) and you add in the formula (under equations)
... realdot(mod1.ec.Ez,mod1.ec.Ez)+eps)^-0.5)...
But most probably you shouldavoid "nofield" by a better BC or initial value conditions
--
Good luck
Ivar