Re: [sparta-users] Help

[Steve P. <sj...@gm...>]

There are 2 options in SPARTA for rotating surfaces.

The first is to use the "rotate" option of the surf_collide command.
You should read its description in the doc page carefully to see if it does
what you want.
Note that in this case the surface elements (e.g. tris) do not actually
move within the simulation domain.
Instead the effect of a rotating surface is simply assigned to particles
when they collide with the tri.
As the doc page explains, there are restrictions on what kind of rotation
can be modeled in this way.

The second is to use the fix move/surf command with its rotate option which
operates dynamically during a simulation.
The doc page for the move_surf command (one-time movement) is also
important to look at.  This can do more
general rotations, but does not model collisions with particles due to
surface movement.  Its meant to do a slow
rotation (relative to particle motion), which the particles re-equilibrate
to between timesteps when the surfaces move.

Steve

On Tue, Jan 20, 2026 at 12:05 AM WUYONGXIN <183...@16...> wrote:

>
> Dear Steve,
>
> Thank you for your prompt reply.
>
> Regarding the rotation, I was referring to simulating rotating components
> (e.g., rotating walls or rotor) in my simulation. Specifically, I would
> like to know how to properly set up the rotation effects in SPARTA—whether
> it should be done through the rotate command in surf_collide or if there
> are other recommended methods. Any guidance or suggestions on this would be
> greatly appreciated.
>
> Thank you for your time and assistance.
> Best regards,
>
> At 2026-01-19 23:38:20, "Steve Plimpton" <sj...@gm...> wrote:
>
> Hi - it looks like the tools/grid_refine.py tool has not been updated to
> use the newer grid file format
> used by the read_grid, write_grid, adapt_grid, and fix_adapt commands.
>
> So we can update the python file to use the common format.
>
> Re: rotation, I'm not sure what you mean.  Do you mean in the context of
> grid adaptation?
> Or just to include rotation effects in collisions?
>
> Steve
>
> On Mon, Jan 19, 2026 at 2:50 AM WUYONGXIN <183...@16...> wrote:
>
>> Dear sparta：
>>      My name is Yongxin Wu, and I am a student from ‌Zhejiang University
>> from China.
>>
>>     When using the grid_refine function in SPARTA to mesh a 3D geometry,
>> a mesh file in parents format is generated. This file cannot be read by the
>> read_grid command. May I ask how to convert it into a cells format file
>> that the program can use? Additionally, if I want to account for the
>> rotational effect of the wall, should I use the rotate command in
>> surf_collide?
>>
>>     Thank you for your time.
>>     Best regards
>>
>>
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>