A cylindrical converging shock tube for shock-interface studies

et al. 2015

J. Fluid Mech.

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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).

mentioning

confidence: 99%

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

Long

et al. 2015

J. Fluid Mech.

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“…For the detailed mathematical formulism and validation, the reader is referred to our previous work (Zhai et al, 2010;Luo et al, 2014). Figure 1 illustrates the schematic of the test section which can directly convert an incident planar shock wave into a cylindrical one.…”

Section: Generation Of Cylindrical Shock Wavesmentioning

confidence: 99%

“…It must be mentioned that so far the RM instability experiments have seldom been performed in such shock tubes probably due to the difficulties in settling the initial interfaces and measuring relevant quantities. Recently, a simple but effective technique for generating cylindrical converging shock waves in an ordinary shock tube was developed based on shock dynamics theory in our group (Zhai et al, 2010;Luo et al, 2014). The present experimental study is motivated by the method, aiming at more potential of this experimental method in study of the RM instability.…”

Section: Introductionmentioning

confidence: 96%

Experimental study of Richtmyer-Meshkov instability in a cylindrical converging shock tube

Luo

2014

Laser Part. Beams

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The interaction of a cylindrical converging shock wave with an initially perturbed gaseous interface is studied experimentally. The cylindrical converging shock is generated in an ordinary shock tube but with a specially designed test section, in which the incident planar shock wave is directly converted into a cylindrical one. Two kinds of typical initial interfaces involving gas bubble and gas cylinder are employed. A high-speed video camera combined with schlieren or planar Mie scattering photography is utilized to capture the evolution process of flow structures. The distribution of baroclinic vorticity on the interface induced by the cylindrical shock and the reflected shock from the center of convergence results in distinct phenomena. In the gas bubble case, the shock focusing and the jet formation are observed and the turbulent mixing of two fluids is promoted because of the gradually changed shock strength and complex shock structures in the converging part. In the gas cylinder case, a counter-rotating vortex pair is formed after the impact of the converging shock and its rotating direction may be changed when interacting with the reflected shock for a relatively long reflection distance. The variations of the interface displacements and structural dimensions with time are further measured. It is found that these quantities are different from those in the planar counterpart because of the shock curvature, the Mach number effect and the complex shock reflection within the converging shock tube test section. Therefore, the experiments reported here exhibit the great potential of this experimental method in study of the Richtmyer-Meshkov instability induced by converging shock waves.

“…Great potential of this shock tube facility was revealed through performing RM instability experiments. 121,125,126 Quantitative results indicated that the converging shock wave promotes the turbulent mixing formation. Based on the principle of annular coaxial vertical diaphragmless shock tube, 113 a similar annular coaxial vertical diaphragmless shock tube with improved interface formation method and flow diagnostic technique was constructed, 122 and the evolution of polygons impacted by cylindrically converging shock wave and its re-shock from center was captured in experiments using laser sheet technique, as indicated in Figure 17 for an octagon.…”

Section: Interaction Of a Converging Shock Wave With A Gaseous Interfacementioning

confidence: 99%

Review of experimental Richtmyer–Meshkov instability in shock tube: From simple to complex

Proceedings of the Institution of Mechanical Engineers, Part C:

Zou

et al. 2017

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Richtmyer–Meshkov (RM) instability is regarded as a central role for understanding the hydrodynamic processes involved in inertial confinement fusion, supersonic combustion and supernova explosion. Because of its academic implication and engineering applications, the RM instability has received much attention since it was proposed. As an important tool for studying RM instability, shock tube experiment on shock–fluid interface interaction has been widely adopted and great progress has been achieved in past decades. The generation of a shock wave, the formation of an initial interface and the diagnostic of flow field are the three elements for studying the RM instability experimentally. This review surveys the advances in experimental investigations of RM instability in shock tube environment. Originating from a simple configuration as a planar shock interacting with a simple perturbed interface, the experimental study of RM instability approaches more complex situations like a convergent shock with a simple interface, or a planar shock with a complex interface. It is then expected that the experimental study on the real circumstance may be realized by using a complex shock with a complex interface. Finally, we propose the following issues for future study: (1) evolution of the RM instability induced by cylindrically converging shock waves; (2) effect of the three dimensions on the RM instability; (3) interaction of perturbed shock wave with an initially uniform or perturbed interface; and (4) formation and mixing mechanism of the compressible turbulence in the final stage of the RM instability.