Discussion Forum

Syed,

The error is caused by incorrect initial conditions. To ensure that the mass fractions sum to one, check the "From mass constraint" box on the argon ground state atom. I'd also generally recommend checking the "Initial value from electroneutrality constraint" box for the argon ion.

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Luke Gritter
AltaSim Technologies

Hello Mr Gritter

Thank you for your reply Sir. I really appreciate the help.

Sir, I included the changes which you told me to, but still the model is not running (attached is my model)

I have coupled my DC discharge to an external circuit (AC). I tried to include a "separate" Drift diffusion interface and an heavy species transport interface. And the problem still persists. Though the drift diffusion model runs with the external circuit but when i include the heavy species transport module, the study again fails.

I also tried to execute the study after removing the dielectric material and it fails yet again.

The error message is the same.

I will really appreciate if you can guide me through this. My final goal is to introduce plasma chemistry in the space near the DBD. Then I want to apply AC to my electrodes and see how the electron and species (argon etc) density changes with time and with changing voltage. Finally, my goal is to calculate the body force which I have figured out. This body force will also change in time as the voltage is changing and plasma characteristics change.

I look forward to your reply.

Thank you

Best regards
Zaid

Zaid,

In the original model that you attached, the changes I mentioned enable the model to run. In the new model you attached, I noticed you had set the argon metastable (Ars) to be determined from mass constraint. This is incorrect - the argon ground state (Ar) should be determined from mass constraint. I noticed a few other problems in the new model:

1) The initial electron density was set impossibly high.
2) You are connecting both electrodes to the circuit. Only one should be connected; the other should be grounded.
3) You haven't included surface reactions for the metastable and ion.
4) You should delete the Electric Currents interface (you don't need it).
5) The circuit implementation is incorrect. I'd suggest using the built-in circuit options on the Electric Potential boundary condition in the DC Discharge interface (at least until you get the other kinks worked out).

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Luke Gritter
AltaSim Technologies

Hello Mr Gritter

I hope this message finds you in the best of your health and vigor. Also, a lot thanks for the advice.

Now, my model converges for atmospheric pressure and with multiple modules. This has allowed me to define my boundary conditions properly. However, comparing my results with computational studies done in the past, my model does does not matches the expected trend. For example: The plasma (indicative by positive ion density) should evolve over the dielectric surface as shown in Fig1, for a positive potential over the exposed electrode. My plasma however does not evolve in this manner.

I feel that this problem can be due to not defining a wall and surface charge accumulation, but when I do that (and i have to do that) the model gives me an error and is unable to calculate the hs.ebar(electron energy density), though I correctly define and route the variables from respective modules.

I have attached my model and the desired boundary conditions (BC.jpg). The Poisson equation is solved for dielectric and the air domain.

It will be very gracious of you if you could help me Sir. I appreciate your help.

Take care and Best regards
Zaid

please, are you find whereis the errors ?