Search NASA⌕ Search

SEARCH · Search NASA

Results for “RAREFIED GAS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

A collision-selection rule for a particle simulation method suited to vector computers

A theory is developed for a selection rule governing collisions in a particle simulation of rarefied gas-dynamic flows. The selection rule leads to an algorithmic form highly compatible with fine grain parallel decomposition, allowing for efficient utilization of supercomputers having vector or massively parallel single instruction multiple data architectures. A comparison of shock-wave profiles obtained using both the selection rule and Bird's direct simulation Monte Carlo (DSMC) method show excellent agreement. The equation on which the selection rule is based is shown to be directly related to the time-counter procedure in the DSMC method. The results of several example simulations of representative rarefied flows are presented, for which the number of particles used ranged from 10 to the 6th to 10 to the 7th demonstrating the greatly improved computational efficiency of the method.

Baganoff, D.↗
NASA NTRSDate not supplied

Design of a Subscale, Inert Gas Test for Plume-Surface Interactions in a Reduced Pressure Environment

Rocket plume-surface interaction is a multi-phase, complex discipline characterized by plume flow physics, erosion physics, and ejecta dynamics. To provide critical data for the validation of predictive modeling capabilities, an inert-gas, subscale ground test has been designed, with one test phase focused on cratering and ejecta and another test phase focused on plume structure and behavior. Using a supersonic, heated N2 jet impinging onto six different mechanical regolith simulants, visual data on the temporal evolution of cratering and ejecta are collected in a vacuum chamber at ambient pressures ranging from 600 Pa down to approximately 7 Pa. Using the same N2 jet impinging onto an instrumented plate, NO planar laser-induced fluorescence data are obtained at lower ambient pressures for the validation of both continuum and rarefied gas-phase physics. This paper discusses the design of this test and data products, with emphasis on the cratering and ejecta experiments, along with the physical scaling, challenges, and relevance of these data to the maturation of the plume-surface interaction discipline.

Ashley M Korzun↗
NASA NTRS1991

Numerical analysis of rarefied slit flows. II - Navier-Stokes simulations

The model problem of pressure-driven flow of a rarefied monatomic gas through a two-dimensional slit is analyzed via full Navier-Stokes numerical simulation. Parametric solutions are generated for slit-height based Knudsen number ranging from continuum to transitional flow and for reservoir pressure ratios leading to subsonic and supersonic flow. The change in the structure of the flowfield near the slit as a function of pressure ratio and Knudsen number are quantified from a purely continuum standpoint. The choice of numerical domain size, boundary conditions and treatment of the slit are also discussed. As expected, comparison with a Direct Simulation Monte Carlo solution for a highly rarefied case shows large differences in the predicted mass flow. The cause of these differences can be quantified through detailed comparison of the local flowfield properties. For the larger pressure ratio cases qualitative trends with increasing rarefaction are discussed, including the change in the sonic line shape in the slit and the in total mass flow.

Wadsworth, D. C.↗
NASA NTRS1966

Omegatron studies of a skimmed beam system.

Continuum source molecular beam facility, examining effect of source-skimmer distance variation on flux and spatial distribution of beam in collimation chamber downstream

MOLECULAR BEAM↗
NASA NTRS1967

Fluid physics

Density disturbance ahead of sphere in rarefied nitrogen or argon supersonic flow, and stability of viscous three-dimensional disturbances in laminar compressible boundary layer

SPHERE↗