Vapor flows from a single channel (tube) and from a set of tubes are s
imulated in the free molecular motion approximation. The integrated ch
aracteristics (the fractions of transmitted, sticking, and reflected p
articles) and the angular distributions of the flux and flux density o
f the vapor are obtained. Calculations of the flux of atoms scattered
as a result of single collisions in an atomic beam are performed. (C)
1998 American Institute of Physics. [S1063-7842(98)01405-6].