Experimental investigation of cylindrical converging shock waves interacting with a polygonal heavy gas cylinder

Abstract

The interaction of cylindrical converging shock waves with a polygonal heavy gas cylinder is studied experimentally in a vertical annular diaphragmless shock tube. The reliability of the shock tube facility is verified in advance by capturing the cylindrical shock movements during the convergence and reflection processes using high-speed schlieren photography. Three types of air/SF 6 polygonal interfaces with cross-sections of an octagon, a square and an equilateral triangle are formed by the soap film technique. A high-speed laser sheet imaging method is employed to monitor the evolution of the three polygonal interfaces subjected to the converging shock waves. In the experiments, the Mach number of the incident cylindrical shock at its first contact with each interface is maintained to be 1.35 for all three cases. The results show that the evolution of the polygonal interfaces is heavily dependent on the initial conditions, such as the interface shapes and the shock features. A theoretical model for circulation initially deposited along the air/SF 6 polygonal interface is developed based on the theory of Samtaney & Zabusky (J. Fluid Mech., vol. 269, 1994, pp. 45-78). The circulation depositions along the initial interface result in the differences in flow features among the three polygonal interfaces, including the interface velocities and the perturbation growth rates. In comparison with planar shock cases, there are distinct phenomena caused by the convergence effects, including the variation of shock strength during imploding and exploding (geometric convergence), consecutive reshocks on the interface (compressibility), and special behaviours of the movement of the interface structures (phase inversion).

On divergent Richtmyer–Meshkov instability of a light/heavy interface

“…The first shock-tube experiment on the convergent RMI was reported in a coaxial shock tube (Hosseini, Ogawa & Takayama 2000;Hosseini & Takayama 2005) and a quicker growth of turbulent mixing zone width than the planar counterpart was observed. Later, the evolution of polygonal and single-mode interfaces impacted by a cylindrical shock was examined with high-speed laser sheet imaging in a similar shock tube (Si et al 2015;Lei et al 2017). Based on shock dynamics theory, a convergent shock tube with a special wall profile which can smoothly convert a planar incident shock into a perfect cylindrical one was designed and manufactured (Zhai et al 2010).…”

Energy convergence of shock waves and its destruction mechanism in cone-roof combustion chambers

“…Besides, most researches concern that shock wave converges towards an apex of a cone or shock wave converges in a two dimensional space. Kjellander et al [21] created spherical shock waves converging to an apex and measured the apparent temperature though the light emitted from the implosion focus; Cates and Sturtevant [22] developed a finite-difference method to estimate the geometrical configuration of complex weak-shock interactions, which is validated by shock wave focusing experiments; Bond et al [23] investigated the behavior of an initially planar shock wave propagating into a linearly convergent wedge experimentally and numerically; Si et al [24] studied the interaction of cylindrical converging shock waves with a polygonal heavy gas cylinder experimentally in a two dimensional space. These researches usually use weak shock waves with small Mach Numbers as an initial perturbation.…”

Progress in experiments of converging Richtmyer-Meshkov instability

“…http://engine.scichina.com/doi/10.1360/N972017-01211 [10] 、气柱 [11] 、气帘 [12] 、单/多模 [13,14] 界面等) 的相互作用 [28,29] 进行过详细的介绍. Si等人 [18] Figure 1 The interaction of a cylindrical shock with a octagonal SF 6 cylinder [18] 评 述 图 2 柱形激波与单模界面相互作用 [30] Figure 2 Interaction of a cylindrical shock with a single-mode interface [30] 形成、激波聚焦以及反射激波-界面相互作用等典型 [32,33] 效应有效促进扰动的增长; 在阶段III, 轻重界面减 速引起的Rayleigh-Taylor (RT) [34,35] Figure 3 Schlieren results showing the interaction of a cylindrical shock interacting with a single-mode interface [31] 评 述 图 4 (网络版彩色)振幅随时间的变化曲线 [31] Figure 4 (Color online) Temporal variation of the perturbation amplitude [31] 中有详细介绍.…”