vacuum model
 

Hi There DSMC folk -

I was thinking about trying to modify one of the wall interaction models to make it a vacuum boundary. I don't have a lot of c++ experience, but in a Fortran90 dsmc code that I have used there was a wall interaction model that basically just a removed a user specified percentage of incident particles while the rest were reflected back according to the wall model (specular or diffuse).

Does it seem possible to just "delete" a percentage or all incident cloud particles? Any thoughts on how this could be implemented?

Thanks.

Hi Hyperion,
I'm not an expert of DSMC (I did some work on it some years ago with Bird's code DS2V, but I didn't used it anymore for years), but it seems that your proposal should be ok.
In particular, it would be possible to modify the specular reflection model in order to remove a quantity of parcels sufficient to obtain a certain number density rhoN, while velocity and temperature (read, energy) are fixed from the interior. Maybe in this way it could be possible to fix a certain number density, and then a certain pressure.
A vacuum boundary means pressure = 0, so you have just to remove all the parcels, I think.

Did you success to implement sucha a modified bc?

Thanks, Ivan