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Record Details

Record 34 of 12207
Rotational Relaxation in Nonequilibrium Freejet Expansions of Heated Nitrogen
Author and Affiliation:
Gochberg, Lawrence A.(National Academy of Sciences - National Research Council, Moffett Field, CA United States)
Hurlbut, Franklin C.(California Univ., Dept. of Mechanical Engineering, Berkeley, CA United States)
Arnold, James O. [Technical Monitor]
Abstract: Rotational temperatures have been measured in rarefied, nonequilibrium, heated freejet expansions of nitrogen using the electron beam fluorescence technique at the University of California at Berkeley Low Density Wind Tunnel facility. Spectroscopic measurements of the (0,0) band of the first negative system of nitrogen reveal the nonequilibrium behavior in the flowfield upstream of, and through the Mach disk, which forms as the freejet expands into a region of finite back pressure. Results compare well with previous freejet expansion data and computations regarding location of the Mach disk and terminal rotational temperature in the expansion. Measurements are also presented for shock thickness based on the rotational temperature changes in the flow. Thickening shock layers, departures of rotational temperature from equilibrium in the expansion region, and downstream rotational temperature recovery much below that of an isentropic normal shock provide indications of the rarefied, nonequilibrium flow behavior. The data are analyzed to infer constant values of the rotational-relaxation collision number from 2.2 to 6.5 for the various flow conditions. Collision numbers are also calculated in a consistent manner for data from other investigations for which is seen a qualitative increase with increasing temperature. Rotational-relaxation collision numbers are seen as not fully descriptive of the rarefied freejet flows. This may be due to the high degree of nonequilibrium in the flowfields, and/or to the use of a temperature-insensitive rotational-relaxation collision number model in the data analyses.
Publication Date: Jan 01, 1994
Document ID:
20020014787
(Acquired Feb 01, 2002)
Subject Category: FLUID MECHANICS AND THERMODYNAMICS
Document Type: Preprint
Contract/Grant/Task Num: RTOP 505-70-91
Financial Sponsor: NASA Ames Research Center; Moffett Field, CA United States
Organization Source: National Academy of Sciences - National Research Council; Moffett Field, CA United States
Description: 1p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
NASA Terms: FREE JETS; NITROGEN; RAREFIED GAS DYNAMICS; LOW DENSITY WIND TUNNELS; MOLECULAR RELAXATION; SHOCK LAYERS; TEMPERATURE MEASUREMENT; COLLISIONS; GAS EXPANSION; FLOW DISTRIBUTION
Availability Source: Other Sources
Availability Notes: Abstract Only
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