Discussion Forum

Posted: 1 decade ago May 6, 2013, 1:24 a.m. EDT

Hi In frequency domain, with amplitude in the "voltage value" and a frequency defined in the frequency domain solver should absolutely give you a voltage drop as result. Are you sure you have boundaries selected in the two BC selection boxes ? And use rather the terminal than "electric potential" in this way you get out directly the lumped port/terminal values as global integrated values -- Good luck Ivar

Posted: 1 decade ago May 6, 2013, 6:38 a.m. EDT

Hello! ES is not defined for frequency domain. Ralf

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• snap.png

Posted: 1 decade ago May 7, 2013, 2:46 a.m. EDT

Hi I would answer yes and no ;) as ES does not allow for current flow, hence no resistance values, and no magnetic fields hence no true L inductance values, only pure capacitances. then the d/dt or omega^1 term can be dropped, Then as you have C alone the d/dt^2 or omega^2 term can also be dropped. which means that even if frequency domain is not solved for, you can still do it without errors, whithin the hypothesis of ES You can compare the results ona simple model (ES and EC) this one is a 4.3b model -- Good luck Ivar

Attachments:

• ESECtst_43b_1.mph

Posted: 1 decade ago May 7, 2013, 5:00 a.m. EDT

Thanks guys for all your help, its much appreciated. I tried running an AC simulation in EC and it worked no problem, however when I disabled frequency domain and ran a stationary study I got a singular matrix error and didn't know how to solve it. So I basically got fed up and created two files. One with ES stationary for DC simulations and one in EC with AC simulations. While we are on topic I am also wanting to study the mechanical effects on a water droplet when subjected to an electric field. Basically my model is a semi-circle defined as water in between two copper plates on an insulating medium. I was thinking of using the fluid flow module either single phase flow or multiphase flow. Any suggestions?

Posted: 1 decade ago May 7, 2013, 5:04 a.m. EDT

Hi if its a water droplet in air, I would suggest two phase flow level set, but perhaps you can consider it as a fixed volume sphere to start with, if the droplet is small 100 nm then the internal pressure is high about 15 atm due to the surface tension Still you should be able to solve both cases in EC, note that you need to define a conductance for your material if you want to see any flow, so air with "0" should be patched to some 1 S/m -- Good luck Ivar

Posted: 1 decade ago May 7, 2013, 9:21 a.m. EDT

Hi Ivar, Yes the water droplet is surrounded by air, positioned on some sort of polymer. The volume of the water droplet will vary from 15uL-100uL. I see the conductance of air is zero. In terms of the EC and ES problem I assume that in both cases the results for stationary will be the same. I'm just curious to know why ES doesn't offer electrical insulation boundary conditions where as EC does and will it effect results?

Posted: 1 decade ago May 7, 2013, 1:48 p.m. EDT

Hi I would say that is because there is no current flow in ES (static) so by default it's "isolated everywhere" those are the basic hypothesis of ES. Indeed air has 0 S/m conductivity in the material library, this is probaby correct (physically) but gives issues for the solver in EC or MEF mode, therefore you need sometimes, to add a little conduction even for "air" -- Good luck Ivar

Posted: 1 decade ago Aug 28, 2013, 8:55 a.m. EDT

I'm also getting the same 0v result. If I use EC, should I enter conductivity values of materials in the domain? [QUOTE] Hi all, I'm currently studying the electromechanical effects of a water droplet under AC/DC voltages. The water droplet is placed between two rectangular electrodes. I've applied a electric potential to one of the electrodes and grounded the other. I currently I have no issue simulating DC conditions in electrostatics, however when I simulate AC conditions I encounter a problem. I disable the stationary study and add frequency domain study. Leaving the magnitude in the electric potential, in the study settings I add a frequency of 50Hz. When I compute the simulation there is no electric potential or electric field. Can someone help. Am I doing this process right or am I missing a step? [/QUOTE]

Posted: 1 decade ago Aug 28, 2013, 9:02 a.m. EDT

It can help to stabilize the solver to assign a small conductivity to insulators. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology