Charged gas in neutral gas
December 30, 2018 at 12:52 pm #2012
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.December 30, 2018 at 5:20 pm #2981
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?December 30, 2018 at 8:12 pm #2982
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.
MJDecember 31, 2018 at 12:49 am #2983
So, if I understand correctly, then using OpenLB it is not possible to simulate a collisionless gas, isn’t it?December 31, 2018 at 9:50 am #2984
We have a model for that scenario (see paper) and a test case in OpenLB that is very simular to it.
MJJanuary 1, 2019 at 11:17 pm #2985
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?January 2, 2019 at 8:49 am #2986
You may change any source file – that is the idea of sharing open source code.
MathiasJanuary 2, 2019 at 1:07 pm #2987
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?January 2, 2019 at 3:16 pm #2988
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.*
MathiasJanuary 2, 2019 at 6:02 pm #2990
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?January 2, 2019 at 6:36 pm #2991
No, static collide will not help you. It collides without updating u. You can look at ConstRhoBRK, that is the one you need.
MathiasJanuary 3, 2019 at 9:34 am #2992
What does “collides without updating u” mean? Does it mean that equilibrium distribution function in collision BGK operator which is f0 = f0(u) does not change during a simulation. And for example I can set u to zero?January 3, 2019 at 10:45 am #2993
Please have a look in the source code.
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