vacuum model

hyperion · November 6, 2010, 15:10

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.

ivan_cozza · January 25, 2011, 04:27

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

November 6, 2010, 15:10	vacuum model	#1
hyperion Member Daniel Join Date: Jul 2010 Location: California Posts: 39 Rep Power: 16	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.

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January 25, 2011, 04:27		#2
ivan_cozza Senior Member Ivan Flaminio Cozza Join Date: Mar 2009 Location: Torino, Piemonte, Italia Posts: 210 Rep Power: 18	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