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Author Topic: Charged gas in neutral gas
kolotinsky
Newbie
Posts: 22
 Charged gas in neutral gason: December 30, 2018, 12:52

Dear Mathias,
is it possible to simulate the following situation with OpenLB? The ion gas, which is affected by an external electric field, is in a neutral gas. The ion gas itself, in our approximation, is collisionless, and only collides with a neutral gas. In my last post, I represented just such a situation and therefore wrote that speed would come to a constant value.

kolotinsky
Newbie
Posts: 22
 Re: Charged gas in neutral gason: December 30, 2018, 17:20

If I add viscosity to external force term to describe collisions with neutral gas can I set zero relaxation frequency in MRT operator or simply use BGK operator with zero relaxation frequency?

mathias
Posts: 316
 Re: Charged gas in neutral gason: December 30, 2018, 20:12

Dear Kolotinsky,

that is a two component system. You may use a simular apporach to

The test case in available by means of the bifiurcatiuon example.

Using only convection and zero difussion is not possible. You need a stabilization simular to the one proposed in the paper.

We will discuss that apporach in our spring school in the LBM theory part as well as in the practical part.

Best
MJ

kolotinsky
Newbie
Posts: 22
 Re: Charged gas in neutral gason: December 31, 2018, 00:49

So, if I understand correctly, then using OpenLB it is not possible to simulate a collisionless gas, isn't it?

mathias
Posts: 316
 Re: Charged gas in neutral gason: December 31, 2018, 09:50

We have a model for that scenario (see paper) and a test case in OpenLB that is very simular to it.

Best
MJ

kolotinsky
Newbie
Posts: 22
 Re: Charged gas in neutral gason: January 1, 2019, 23:17

My aim is to simulate the following equation
df/dt + v*df/dr + (F/m)*df/dv = w*(f-f0)
As I understand in OpenLb algorithm for this case f0 is shifted maxwell distribution.
I suppose to simulate collisionless ion gas in neutral gas it is enough to replace shifted maxwell distribution function of ions with maxwell distribution function of neutral gas. How can I apply my idea using OpenLB? Is it possible to change some source file to implement my idea?

mathias
Posts: 316
 Re: Charged gas in neutral gason: January 2, 2019, 08:49

You may change any source file - that is the idea of sharing open source code.

Best
Mathias

kolotinsky
Newbie
Posts: 22
 Re: Charged gas in neutral gason: January 2, 2019, 13:07

I understand this. I mean, could you advice me which file should I rewrite to change equilibrium distribution function for MRT or BGK forced dynamic?

mathias
Posts: 316
 Re: Charged gas in neutral gason: January 2, 2019, 15:16

You can use our dogygen html Version https://www.openlb.net/DoxyGen/html/index.html to find and work with the code. It is in core/dynamics.*

Best
Mathias

kolotinsky
Newbie
Posts: 22
 Re: Charged gas in neutral gason: January 2, 2019, 18:02

I have found interesting method named "staticCollide" in doxygen. I suppose it can help me for my purpose. But I do not really understand what this method do. Could you explain it for me?

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