N2-O2 mixture - external profile of electric field

[Tanguy]

Hello everyone!

I'm trying to run a simulation based on the example 4.

I use the kinet_N2_O2_v1.03 kinetics input file and provide an electric field profile (nanosecond discharge, peak at ≈300 Td).

My Fortran main code is very simple: at every iteration I set the electric field to be equal to the value from my external electric field profile and then call ZDPlasKin_timestep.

I don't encounter any error and most of the results seem correct.

However, the electrons density is almost constant (I would expect a sharp increase following the electric field peak) and therefore the current density profile is also wrong.

I tried to modify the time step, smoothen the electric field profile, change the initial electrons density but without success.

Does anyone know why the electrons density computation is wrong? And how to fix it?

Thank you!

Tanguy

[Nicolas Minesi]

Hello Tanguy,

Welcome in the amazing world of ZDPlaskin and ns discharges!

What is the plasma temperature and which reactions are expected to produce electrons (N2 + e => N2+ + 2e-)? Did you try with a constant reduced field to see if that works?

Nicolas Minesi

[Tanguy]

Hello Nicolas,

Thank you for your reply!

The temperature and pressure conditions are: 300K, 200 Torr.

The reactions producing electrons are:

e + N      => e + e + N^+                

e + O      => e + e + O^+              

e + N2     => e + e + N2^+                   

e + O2     => e + e + O2^+                      

e + NO     => e + e + NO^+                      

e + N2O    => e + e + N2O^+

But for this first test case, I'm simply considering pure N2.

A constant reduced field does work: using a 200Td reduced field, ionization happens and as expected, I get a quick increase of the electrons density.

My goal is to compare my simulation results with experimental data from literature.

Using the experimental reduced electric field as an input for my code (peak at ≈300 Td), production of electrons through ionization is somehow not activated and the electrons density remains roughly constant.

Therefore I just created a new reduced electric field profile as shown below.

With a peak that is significantly higher (≈470 Td) I manage to make my results fit the experimental data.

Do you have any idea why there is this gap between ZDPlasKin results and experiments?

Best regards,

Tanguy

[Nicolas Minesi]

Hello,

Do you have any idea why there is this gap between ZDPlasKin results and experiments?

It is a very difficult question :) ZDPlasKin is a good tool that is able to provide results close to experimental ones. You know have to check your inputs and chemical mechanism. Good luck!

Nicolas

[Tanguy]

Hello Nicolas,

Thank you for your reply!

Sorry my question was pretty general, I will have a closer look at the input files.

Tanguy