Shock-Tube Boundary-Layer Growth Effects on Reflected-Shock Conditions in Bath Gases with and without CO2
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2017 by The authors. The disturbances created by boundary layers behind incident shock waves are minimal, but are multiplied in the post-reflected shock region and contribute to non-ideal behaviors in this region. In this study, a boundary-layer model was used to confirm the link between predicted incident-shock boundary-layer growth and post-reflected shock pressure rise in shock tubes for a wide variety of non-reacting mixture compositions and experimental conditions. The results show that boundary-layer growth and, consequently, post-reflected shock pressure rise are strongly affected by the incident-shock Mach number and specific heat ratio, , of the mixture. In this study, mixtures of AR, N2, and 0. 21. N2/CO2were examined at experimental conditions of approximately 1400-1800 K at an average pressure of 1.73 atm. Although each mixture (with differing ) experienced the same range of post-reflected shock conditions (T5, P5), the Mach number span for each mixture was different. This Mach number by-product of matching T5and P5for each mixture is a major cause of differences in boundary-layer growth behavior and resulting post-reflected shock pressure rise, with the CO2-laden mixture producing the largest post-shock pressure (and temperature) rise. Additionally, the measured pressure rise for the high-CO2-content mixtures was an order of magnitude greater than for mixtures of pure Ar at the same experimental (T5, P5) conditions.
