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More services...Dielectrophoresis simulations or gradient of electric field
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3 Replies
Last post: February 6, 2012 8:13am UTC
February 6, 2012 5:48am UTC
Dielectrophoresis simulations or gradient of electric field
Hi,
I am doing dielectrophoresis simulations using simulations. Basically I use AC/DC module -conductive medium DC to get the electric field distribution. But I face some problems geting gradient of electric field. I tried some methods of previous threads but was not successful.
I have some questions.
1. If I want to extract gradient of electric field in x direction, I define d(Ex_dc^2,x) in global expressions. Is that right ?
2. The bias is a AC voltage but I only know how to apply a DC voltage. Anyone knowing what module should I use then. I simplify the problems by doing DC simulation.
Anyone doing this kind of simulations? We can discuss together... Thanks.
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February 6, 2012 6:26am UTC in response to Song Liu
Re: Dielectrophoresis simulations or gradient of electric field
Hi
in EC or electric currrent you solve for "V" the voltage, and find the electric field (Ex,Ey,Ez)=-grad(V) so you are already taking a first derivative of V. now if you want to derivative of the field Ex you are asking for the 2nd derivative of a dependent variable, this is only possible if you are using a 2nd order (or preferrably higher) shape function, and that your mesh is of sufficient quality (symmetric) to allow such high order shape functions
Whn you apply AC currents, you should consider the frquency domain solver, this does a development of the ime derivativeinto the harmonic representation with omega = 2*pi*f, you define the amplitude and the phase ans well as the frequency in latter in the solver section (or frequency range for a scan) and off you go.
Check the doc and the examples in the model library
--
Good luck
Ivar
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February 6, 2012 6:51am UTC in response to Ivar Kjelberg
Re: Dielectrophoresis simulations or gradient of electric field
Hi, Ivar,
Thanks for your reply.
I saw the pre-defined expression for electric field, norm: normE_dc; x component: Ex_dc; y component: Ey_dc;
Now I want to get grad(E^2) in the x direction. I write it as d(Ex_dc^2,x) but it still give zero value...
I checked some previous thread but can't figure it out...
http://www.comsol.com/community/forums/general/thread/4711/
http://www.comsol.com/community/forums/4-1/thread/17498/
For AC simulations, all I need to do is to change the solver parameter ?
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February 6, 2012 8:13am UTC in response to Song Liu
Re: Dielectrophoresis simulations or gradient of electric field
I think there should be something wrong with my plots. How could I plot the global expression at each point and give a surface plots ?
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