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Drift Diffusion and Heavy species transport coupling

Posted 23 mar 2015, 11:53 GMT-4 Low-Frequency Electromagnetics, Plasma Physics, RF & Microwave Engineering, Fluid & Heat, Interfacing, Computational Fluid Dynamics (CFD), Chemical Reaction Engineering, Modeling Tools & Definitions, Parameters, Variables, & Functions, Results & Visualization, Studies & Solvers Version 4.2, Version 4.4, Version 5.0, Version 5.1 4 Replies

Syed Zaid Ali
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Hello

I am modelling an AC-DBD plasma actuator (model is attached). I have modeled my time-dependent ac circuit and have proceeded to include the drift diffusion model and heavy species transport module to include the plasma chemistry and calculate the electron density and mean electron energy (output from drift diffusion). In my perspective, i have coupled the heavy species module and drift diffusion properly. But on running the simulation, the solver shows an error stating:

Failed to evaluate variable Jacobian.
- Variable: comp1.hs.ebar
- Geometry: 1
- Domain: 1 4
- Feature: Time-Dependent Solver 1 (sol1/t1)

I have several questions
1- How can i resolve the above problem?

2- I also want to derive an expression for body force after i include the fluid module (laminar and incompressible flow). Will it be possible? The body force calculation requires the charge density and electric field. I can output the value of electric field using comsol and i think i can do the same with the charge density (correct me if i am wrong). But the model should also plot the body force vectors (preferably) under the results section. Will this be possible with the capabilities of comsol 4.4 or higher versions?

I sincerely appreciate your help in this regards.

Thank you

Best regards
Zaid
4 Replies Last Post 24 mag 2015, 12:00 GMT-4
Luke Gritter Certified Consultant
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Posted: 9 years ago 24 mar 2015, 14:37 GMT-4
Zaid,

Instead of coupling several physics interfaces together, you should use the either the DC Discharge or the Capacitively Coupled Plasma physics interface. These interfaces contain the functionality of the Drift Diffusion, Heavy Species Transport, and Electrostatics physics interfaces already coupled together.

As you mentioned, the body force is simply the space charge density (dc.scharge in the DC Discharge interface) times the electric field. To apply this body force to the momentum equations in a fluid flow, you need to add a Volume Force to the fluid flow interface (e.g. the Single Phase Flow interface) and enter the components of the body force (dc.scharge*dc.Ex, etc.). These same body force components can be entered as expressions on an Arrow Surface plot to display the force vectors.

--
Luke Gritter
AltaSim Technologies
Zaid, Instead of coupling several physics interfaces together, you should use the either the DC Discharge or the Capacitively Coupled Plasma physics interface. These interfaces contain the functionality of the Drift Diffusion, Heavy Species Transport, and Electrostatics physics interfaces already coupled together. As you mentioned, the body force is simply the space charge density (dc.scharge in the DC Discharge interface) times the electric field. To apply this body force to the momentum equations in a fluid flow, you need to add a Volume Force to the fluid flow interface (e.g. the Single Phase Flow interface) and enter the components of the body force (dc.scharge*dc.Ex, etc.). These same body force components can be entered as expressions on an Arrow Surface plot to display the force vectors. -- Luke Gritter AltaSim Technologies
Syed Zaid Ali
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Posted: 9 years ago 24 mar 2015, 14:51 GMT-4
Thank you for the guidance Mr Gritter. Sir, actually i have to make use of only AC voltage, thus including the electric current and electric circuit interfaces. A reason being that later i will also use my model to optimize the performance of my DBD Plasma actuator by varying the applied AC waveforms and seeing which one is the best. For example, studies in the past have shown that a square waveform outperforms the sine waveform in discharge in terms of induced velocity (due to body force).

Thus my study is to be strictly focused on AC-DBD's (please see my model attached in previous message). Also there are differences in operating conditions and discharge characteristics of a DC-Discharge and CCP versus AC_DBD. My study is focused for aerospace applications of plasma actuators at atmospheric pressure. One reason of preferring AC-DBD over DC discharge is that the breakdown electric field for for AC-DBD is much less than for DC-DBD. This is preferred for aerospace applications.

Could you please suggest me how to approach this problem further in Comsol. I really appreciate the help.

Thank you Mr Gritter

Best regards
Zaid
Thank you for the guidance Mr Gritter. Sir, actually i have to make use of only AC voltage, thus including the electric current and electric circuit interfaces. A reason being that later i will also use my model to optimize the performance of my DBD Plasma actuator by varying the applied AC waveforms and seeing which one is the best. For example, studies in the past have shown that a square waveform outperforms the sine waveform in discharge in terms of induced velocity (due to body force). Thus my study is to be strictly focused on AC-DBD's (please see my model attached in previous message). Also there are differences in operating conditions and discharge characteristics of a DC-Discharge and CCP versus AC_DBD. My study is focused for aerospace applications of plasma actuators at atmospheric pressure. One reason of preferring AC-DBD over DC discharge is that the breakdown electric field for for AC-DBD is much less than for DC-DBD. This is preferred for aerospace applications. Could you please suggest me how to approach this problem further in Comsol. I really appreciate the help. Thank you Mr Gritter Best regards Zaid
Luke Gritter Certified Consultant
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Posted: 9 years ago 24 mar 2015, 15:00 GMT-4
Zaid,

Despite the name, the DC Discharge physics interface can be used for DBD plasmas with any waveform. Depending on the type of circuit you want to couple to the electrode, you may need to also use the Electric Circuits interface.

--
Luke Gritter
AltaSim Technologies
Zaid, Despite the name, the DC Discharge physics interface can be used for DBD plasmas with any waveform. Depending on the type of circuit you want to couple to the electrode, you may need to also use the Electric Circuits interface. -- Luke Gritter AltaSim Technologies
Dwekat
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Posted: 9 years ago 24 mag 2015, 12:00 GMT-4

Zaid,

Despite the name, the DC Discharge physics interface can be used for DBD plasmas with any waveform. Depending on the type of circuit you want to couple to the electrode, you may need to also use the Electric Circuits interface.

--
Luke Gritter
AltaSim Technologies


Luke , Hi ;

Can i use the DC discharge to model a SF6 electric arc ? if no , which plasma model you recommend ?

Regards ;
[QUOTE] Zaid, Despite the name, the DC Discharge physics interface can be used for DBD plasmas with any waveform. Depending on the type of circuit you want to couple to the electrode, you may need to also use the Electric Circuits interface. -- Luke Gritter AltaSim Technologies [/QUOTE] Luke , Hi ; Can i use the DC discharge to model a SF6 electric arc ? if no , which plasma model you recommend ? Regards ;

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