Shock waves and phase changes in a large-heat-capacity fluid emerging from a tube
1986; Cambridge University Press; Volume: 166; Issue: -1 Linguagem: Inglês
10.1017/s0022112086000046
ISSN1469-7645
AutoresP. A. Thompson, G. C. Carofano, Yoongon Kim,
Tópico(s)Computational Fluid Dynamics and Aerodynamics
ResumoThe emergence of a shockwave from the open end of a shock tube is studied, with special emphasis on test fluids of high molar heat capacity, i.e. retrograde fluids. A variety of wavelike vapour-liquid phase changes are observed in such fluids, including the liquefaction shock, mixture-evaporation shock, condensation waves associated with shock splitting and liquid-evaporation waves (these phenomena have analogues in the polymorphic phase changes of solids; only the first two are treated in this paper). The open end of the shock-tube test section discharges into an observation chamber where photographs of the emerging flow are taken. Calculations were performed with the Benedict-Webb-Rubin, van der Waals and other equations of state. Numerical (finite-difference) predictions of the flow were made for single-phase and two-phase flows: solutions were tested against the experimental shock diffraction and vortex data of Skews. The phase-change properties of the test fluid can be quantified by the 'retrogradicity' r(T), measuring the difference in slope between the P, T isentrope and the vapour-pressure curve, and the 'kink' k(T), measuring the difference between the single-phase and mixture sound speeds. Mixture-evaporation (i.e. rarefaction) shocks appear to have a sonic-sonic or double Chapman-Jouguet structure and show agreement with amplitude predictions based on k(T). Liquefaction shocks are found to show a reproducible transition from regular, smooth shock fronts to irregular, chaotic shock fronts with increasing shock Mach number. This transition can be correlated with published stability limits.
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