The flow through orifices and slits is of great technical interest.
The gas can flow either from one gas reservoir into another or into vacuum.
The gas reservoir is serparated from the second reservoir or the vacuum by an orifice.
The mass flow rate per unit area is the quantity of interest.
The image below shows two gas reservoirs separated by a wall. The lower edge of the image is the plane of symmetry.
PI-DSMC was used to study various variants of this geometry.
In order to verrify PI-DSMC V4, the flow through a channel into a vacuum was simulated. As shown in the graph below, the obtained values are in perfect agreement with the results reported in the literature.