Regions and Transitions of Nonstationary Oblique Shock-Wave Diffractions in Perfect and Imperfect Gases.

Abstract : The diffraction of shock waves (2 or = M sub s or = 8) in perfect and imperfect nitrogen and argon by sharp compressive corners (2 deg or = Theta sub w or = 60 deg) were investigated analytically and experimentally. It is shown that seven shock-wave diffraction domains exist in nitrogen and six in argon in the ranges 1 or = M subs or = 10 and 0 deg or = Theta sub w or = 90 deg. The domains consist of the four well-known shock wave reflections, i.e., regular reflection (RR), single-Mach (SMR), complex-Mach (CMR) and double-Mach (DMR) reflections. All the transition boundaries between these regions were established analytically and substantiated by the present experimental results as well as the data from other sources. Over 100 experiments were conducted in the UTIAS 10 x 18 cm Hypervelocity Shock Tube equipped with a 23-cm dia field of view Mach-Zehnder interferometer equipped with a dual-frequency laser light source. It is shown that real-gas effects have a significant influence on the size of the regions and their transition boundaries. Some comparison between steady and nonstationary reflections are made and discussed. Isopycnics (lines of constant density) as well as density distributions along the wedge surface are presented for the various diffraction processes and their differences and similarities are discussed. (Author)