integrated quantity functions

ekhilore · July 7, 2011, 07:14

Hello,

I want to define an expression with a non-scalar variable, (it would be a source, S=j*V), where j is the current density and is a 3Dvector).

If I try to define an expression I get an error telling that I haveto use integrated qunatity functions. I have been trying to get a tutorial, reading manuals and so on, but I haven't been able to understand what I have to do.

If any one could help me.
Thanks in advanced.

stumpy · July 7, 2011, 09:06

What are the full expressions? Are you trying to do Joule heating?

ekhilore · July 7, 2011, 09:53

Hi,

No I'm trying to simulate an electrical contact resistance as a source on the energy equation.
The expresion that I want to define for that sorce has to be
Sarea= j (vectorial sum of the current density, A/m2)*V(a certain value of voltage, a constant, for example 19V)

And I don't know how can I get the vectorial sum of the j and how to use it as a variable.

Thnak you very much

stumpy · July 7, 2011, 10:59

I think you'll need Additional Variables (AV) to do this. J is equal to the conductivity multiplied by the gradient of the electric potential (I think, pls check!). So you'll need an AV for the electric potential then another AV for J.
The AV for electric potential should be a scalar AV, set to solve Poisson Equation, with the Kinematic Diffusivity equal to Electrical Conductivity/Density. You'll probably need to add in a factor to get the units correct.
The AV for J will be a vector AV, with the X component equal to:
Electrical Conductivity*Electric Potential.Gradient X

July 7, 2011, 07:14	integrated quantity functions	#1
ekhilore New Member Join Date: Nov 2010 Posts: 6 Rep Power: 16	Hello, I want to define an expression with a non-scalar variable, (it would be a source, S=j*V), where j is the current density and is a 3Dvector). If I try to define an expression I get an error telling that I haveto use integrated qunatity functions. I have been trying to get a tutorial, reading manuals and so on, but I haven't been able to understand what I have to do. If any one could help me. Thanks in advanced.

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July 7, 2011, 09:06		#2
stumpy Senior Member Join Date: Apr 2009 Posts: 531 Rep Power: 21	What are the full expressions? Are you trying to do Joule heating?

July 7, 2011, 09:53		#3
ekhilore New Member Join Date: Nov 2010 Posts: 6 Rep Power: 16	Hi, No I'm trying to simulate an electrical contact resistance as a source on the energy equation. The expresion that I want to define for that sorce has to be Sarea= j (vectorial sum of the current density, A/m2)*V(a certain value of voltage, a constant, for example 19V) And I don't know how can I get the vectorial sum of the j and how to use it as a variable. Thnak you very much

July 7, 2011, 10:59		#4
stumpy Senior Member Join Date: Apr 2009 Posts: 531 Rep Power: 21	I think you'll need Additional Variables (AV) to do this. J is equal to the conductivity multiplied by the gradient of the electric potential (I think, pls check!). So you'll need an AV for the electric potential then another AV for J. The AV for electric potential should be a scalar AV, set to solve Poisson Equation, with the Kinematic Diffusivity equal to Electrical Conductivity/Density. You'll probably need to add in a factor to get the units correct. The AV for J will be a vector AV, with the X component equal to: Electrical Conductivity*Electric Potential.Gradient X