Disable position integration for fixed bed heat transfer simulation

Submitted by JoG on Wed, 10/18/2017 - 10:17


I am modifing the heat transfer model and would like to test it in a fixed particle arrangement. I can simulate this as usual, but therefore the timestep has to be quite small. I wonder if I could deactivate the particle motion, so that just the heat transfer is solved? Then I could choose a way bigger timestep.

I tried to set pair style to none, but this is not possible since the heat transfer fix requires a pair style. And if I remove the integration fix, the temperature is also not calculated.

I came to the conclusion, that it is not possible and that I would need to modify the soruce code and recompile. Would you agree or is there any other option?

Thank you for your help or just your thoughts on it.

medvedeg | Wed, 10/18/2017 - 17:17

Dear JoG,

you can swtich off "fix nve/sphere" to disable particle motion. Or create a copy of this fix and disable corresponding lines of code, where the positions (x[i][j]) are updated

Alexander Podlozhnyuk

ssong | Mon, 02/18/2019 - 09:08

hi, Podlozhnyuk.

I'm trying to simulate "flow past a fixed sphere".

but, I haven't found yet an exact way to hold the sphere's position while calculating the drag force acting on the sphere.

could you explain more about adding the code above?

thank you in advance.


ssong | Mon, 02/25/2019 - 05:49

Hi, mschramm.

Thank you first for your reply.

I searched for some commands related to this.

But, as I know as, Fix freeze command not only constrains the movement of particles, but also the drag force acting on them.

I want to calculate the drag force of the fixed particle depending on the Reynolds number.

Until now, I have tested for fix freeze, move, velocity and nve/limit, but it seems that the drag on the particle is not calculated properly.

Do you know the solution to this problem?

thanks in advance.


luisjau8967 | Sun, 04/26/2020 - 16:43

Hi ssong,
Did you find how to freeze the particles while outputting the drag force?. I'm also trying to simulate the flow past a sphere. I'm currently using the fix freeze command but I cannot find a way to output the drag force before it being zeroed out.
Thanks in advance!


hamedhoori | Mon, 09/14/2020 - 12:53

Hi, dear Ssong
Did you able to fix the sphere position with calculating the drag force on them? Did you write new fix command for this problem, or the current command of liggghts were enough? If you know the solution I'll be grateful if you could share.
Thanks in advance