Accession Number : AD0602977

Title :   DISTRIBUTION FUNCTION MEASUREMENTS IN RAREFIED GAS FLOW THROUGH AN ORIFICE,

Descriptive Note : Technical rept.

Corporate Author : VIRGINIA UNIV CHARLOTTESVILLE

Personal Author(s) : Scott,John E. ,Jr. ; morton,Harold S. ,Jr. ; phipps,John A. ; Moonan,John F.

Report Date : JUL 1964

Pagination or Media Count : 35

Abstract : Distribution functions in argon and xenon beams that were formed by effusion through a plane orifice have been measured over a range of source density levels corresponding to source Knudsen numbers from 10 to 0.1. For source Knudsen numbers greater than about 5, it was not possible to detect directly the dependence of the differential beam intensity on source Knudsen number; i.e., departures from the Maxwell-Boltzmann distribution function corresponding to the 'collisionless limit' were within the experimental error. As the source density is increased, the most probable beam speed is observed to increase and the width of the distribution is observed to decrease. These effects, which are recognizable as the beginning of a trend away from free molecular flow toward continuum or aerodynamic flow through the source orifice, are clearly evident even when the source Knudsen number is as large as 3. The experimentally measured beam speed distributions are compared with distributions calculated by solving the Boltzmann equation along the beam axis in an approximate manner using the BGK relaxation time model for the collision term. The approximate theory is in qualitative agreement with the experimental results for source Knudsen numbers of order unity. (Author)

Descriptors :   (*RARE GASES, GAS FLOW), (*GAS FLOW, DYNAMICS), (*FLUID MECHANICS, STATISTICAL FUNCTIONS), (*ORIFICES, TRANSPORT PROPERTIES), EXPERIMENTAL DATA, ARGON, XENON, MOLECULAR BEAMS, AERODYNAMIC CHARACTERISTICS

Distribution Statement : APPROVED FOR PUBLIC RELEASE