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The Effect of Vibrational Relaxation of the Discharge Coefficient of Critical Flow Venturis



Aaron N. Johnson, John D. Wright, Shin-ichi Nakao, C L. Merkle, Michael R. Moldover


This paper identifies a new mechanism that can affect the discharge coefficient of critical nozzle flows. Specifically, vibrational relaxation effects are demonstrated to significantly influence the discharge coefficient of selected gases in critical ventrui flows. This phenomenon explains why certian gases - like carbon dioxide - exhibit calibration characteristics that differ significantly from other gases (e.g., N2, O2, Ar, He and H2). A mathmatical model is developed which predicts this behavior, and vibrational non-equilbrium effects are further substantiated by two independent experiments.
Flow Measurement and Instrumentation
No. 4


coefficient, critical flow nozzles, venturi flows
Created December 1, 2000, Updated February 17, 2017