Re: [sparta-users] Surface and flow mesh resolutions

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

Hi - not sure what your question is.  Are the outputs you are showing for a
single timestep,
or cumulative Nscoll Nscheck for a long run?  You could also post your
input files.
How many procs are you running on?  When you say "slow", is that a Q or
comment or what?

Nscheck of 44M with only Nscoll of 400K means you probably have grid cells
with lots of surface
elements in them.  That can indicate you need a finer resolution grid.

Steve

On Thu, Mar 16, 2023 at 6:56 AM Zuheyr Alsalihi <zuh...@vk...>
wrote:

> Dear Colleagues,
>
> I am not new to Sparta but I am mostly moving in the dark due to lack of
> time, despite the very valuable community help I get here.
>
> I have a small model of 5mm x 4mm x 0.5mm at high Kn flow but still with
> collisions, density about 1.4e+16 /m^3.
>
> I normally choose the flow mesh resolution from the principles of at least
> around 15 particles in a cell, and particle travel time in the cell,
> usually time step is 1/3rd of the particle travel time. The surface mesh
> usually coarsest mesh with well surface definition.
>
> *My question is the meaning of the  Nscoll Nscheck variables and their
> reasonable orders.*
>
> With 100 x 50 x 30 flow mesh and  31000 element surface mesh:
> Nscoll=401,414, Nscheck=289,249,273, Natt=0, Ncoll=0, 11k particles.
>
> Same flow mesh with a surface mesh of 3500 elements, and same number of
> particles:
> Nscoll=398264  and Nscheck=44803563.
>
> Slow... Can you please share your ideas? This is a very basic question.
>
> Many thanks for reading.
>
> Zuheyr
>
>
>
>
>
>
> Dr. Zuheyr Alsalihi
> Senior Research Eng.
> von Karman Institute
> 72, Chee. de Waterloo
> 1640 Rhode-St-Genese, Belgium.
> +32 359 98 65
> +32 473 69 32 27
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