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

2015 ◽  
Vol 784 ◽  
pp. 225-251 ◽  
Author(s):  
Ting Si ◽  
Tong Long ◽  
Zhigang Zhai ◽  
Xisheng Luo
Keyword(s):  
Shock Waves ◽  
Shock Tube ◽  
High Speed ◽  
Initial Conditions ◽  
Laser Sheet ◽  
Imaging Method ◽  
Gas Cylinder ◽  
Diaphragmless Shock Tube ◽  
Converging Shock Waves ◽  
Heavy Gas

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/SF6 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/SF6 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).

scholarly journals Development of Shock-Wave-Powered Actuators for High Speed Positioning (Second Report: Characteristics of Diaphragmless Shock Tube and Responsiveness of Actuator)

2013 ◽  
Vol 7 (5) ◽  
pp. 558-563
Author(s):  
Akira Kotani ◽  
◽  
Toshiharu Tanaka ◽  
Akira Hirano ◽  
Keyword(s):  
Shock Wave ◽  
High Pressure ◽  
Shock Waves ◽  
Shock Tube ◽  
High Speed ◽  
Industrial Robots ◽  
Piston Motion ◽  
Diaphragmless Shock Tube ◽  
High Responsiveness ◽  
Piston Speed

Shock tubes experiments are conducted on applications of shock waves to the actuator. The high-pressure and low-pressure sections of a general shock tube are separated by a diaphragm. In this study, a shock wave is generated by “diaphragmless shock tube” which is divided into two sections by a driver piston instead of the diaphragm. We have previously reported on the motion of a driven piston powered by a shock wave. However, not only piston speed but also high responsiveness is required for practical actuators used on manufacturing lines, in industrial robots, etc., The diaphragmless shock tube constructed in this paper is structured to be able to examine not only the motion of the driven piston but also the motion of the driver piston. In addition, the responsiveness of the piston motion of the actuator powered by shock waves is examined. It follows from what has been said thus far that a shock wave can be applied to an actuator with high responsiveness.

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

2014 ◽  
Vol 32 (3) ◽  
pp. 343-351 ◽  
Author(s):  
Ting Si ◽  
Zhigang Zhai ◽  
Xisheng Luo
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Test Section ◽  
High Speed ◽  
Mie Scattering ◽  
Gas Bubble ◽  
Reflected Shock ◽  
Gas Cylinder ◽  
Converging Shock Waves ◽  
The Impact

AbstractThe 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.

Generation of Cylindrical Converging Shock Waves in a Conventional Shock Tube

2015 ◽  
pp. 1077-1082 ◽  
Author(s):  
L. Biamino ◽  
G. Jourdan ◽  
C. Mariani ◽  
L. Houas ◽  
M. Vandenboomgaerde ◽  
...  
Keyword(s):  
Shock Waves ◽  
Shock Tube ◽  
Converging Shock Waves

scholarly journals Bubble dynamics in a compressible liquid in contact with a rigid boundary

2015 ◽  
Vol 5 (5) ◽  
pp. 20150048 ◽  
Author(s):  
Qianxi Wang ◽  
Wenke Liu ◽  
A. M. Zhang ◽  
Yi Sui
Keyword(s):  
Shock Waves ◽  
Thin Layer ◽  
High Speed ◽  
Bubble Radius ◽  
Time History ◽  
Bubble Surface ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Imaging Method ◽  
Rigid Boundary

A bubble initiated near a rigid boundary may be almost in contact with the boundary because of its expansion and migration to the boundary, where a thin layer of water forms between the bubble and the boundary thereafter. This phenomenon is modelled using the weakly compressible theory coupled with the boundary integral method. The wall effects are modelled using the imaging method. The numerical instabilities caused by the near contact of the bubble surface with the boundary are handled by removing a thin layer of water between them and joining the bubble surface with its image to the boundary. Our computations correlate well with experiments for both the first and second cycles of oscillation. The time history of the energy of a bubble system follows a step function, reducing rapidly and significantly because of emission of shock waves at inception of a bubble and at the end of collapse but remaining approximately constant for the rest of the time. The bubble starts being in near contact with the boundary during the first cycle of oscillation when the dimensionless stand-off distance γ = s / R m < 1, where s is the distance of the initial bubble centre from the boundary and R m is the maximum bubble radius. This leads to (i) the direct impact of a high-speed liquid jet on the boundary once it penetrates through the bubble, (ii) the direct contact of the bubble at high temperature and high pressure with the boundary, and (iii) the direct impingement of shock waves on the boundary once emitted. These phenomena have clear potential to damage the boundary, which are believed to be part of the mechanisms of cavitation damage.

Development of a Large Diameter Diaphragmless Shock Tube for Gas-Dynamic Laser Studies

2007 ◽  
Vol 566 ◽  
pp. 9-14 ◽  
Author(s):  
I. da S. Rego ◽  
K.N. Sato ◽  
S. Kugimiya ◽  
T. Aoki ◽  
Y. Miyoshi ◽  
...  
Keyword(s):  
Shock Waves ◽  
Shock Tube ◽  
Large Diameter ◽  
Gaseous Mixtures ◽  
Gas Dynamic ◽  
Diaphragmless Shock Tube ◽  
Good Accordance ◽  
Basic Characteristics ◽  
And Performance

This paper reports on the design and performance of a large diameter diaphragmless shock tube that has been recently developed in order to experimentally study various basic characteristics of the gas-dynamic laser (GDL). The main engineering element of the shock tube is a diaphragm-like sliding piston (in place of a rupturing diaphragm) by which normal shock waves are formed. The role of such a structure in generating repeatable shock waves is discussed. The shock tube performs in good accordance with the simple shock tube theory, as has been verified so far by experiments with some conventional lasing gases (gaseous mixtures of CO2 and N2 and those diluted with an excess of He) at shock wave Mach numbers ranging from 1 to 5. Recent results of the stagnation conditions achieved in the shock tube with application to GDL experiments are included as well.

An experimental study of transverse ionizing MHD shock waves

1968 ◽  
Vol 2 (4) ◽  
pp. 633-652 ◽  
Author(s):  
Charlles F. Stebbins ◽  
George C. Vlases
Keyword(s):  
Magnetic Field ◽  
Shock Waves ◽  
High Speed ◽  
Initial Conditions ◽  
Easy Access ◽  
Low Speed ◽  
Wide Range ◽  
Image Position ◽  
Shock Jump Relations ◽  
The Magnetic Field

The jump conditions across a transverse ionizing MHD shock wave, where the magnetic field is in the plane of the shock, are examined. The conservation laws, in conjunction with Maxwell's laws and the equation of state, yield three jump equations in four unknowns. To uniquely describe jumps across an ionizing wave requires an additional descriptive relationship. The theory of Kulikovskii & Lyubimov and, later, Chu, in which the internal structure of the shock itself supplies the missing relationship, is examined. In particular, Kulikovskii & Lyubimov show, for appropriate ratios of thermal to magnetic diffusivities, that for low-speed waves the magnetic field compression across the shock is unity and the jump equations reduce to the ordinary Rankine—Hugoniot relations. For high-speed shock waves, the magnetic field compression, B2/B1, equals the gas compression across the wave, p2/p1, and the jump equations become the magnetohydrodynamic shock jump relations. Furthermore, intermediate speed shocks induce magnetic field compressions between 1 and p2/p1. An experiment was performed in an inverse pinch where E behind the shock, the shock and piston velocities, and the magnetic field compression across the shock, were measured over a wide range of initial conditions and shock velocities in hydrogen. The jump relations were written with B2/B1 as a parameter and programmed into a digital computer. The program was written for real, equilibrium hydrogen. The program provided easy access to a unique solution of the jump equations for any B2/B1. The experiment tends to confirm the Kulikovskii—Lyubimov—Chu theory. Ordinary shock waves were observed at low speeds and near-MilD shocks were observed at high speeds. Further, the relation was verified for the plasma behind the shock for low-speed shock waves, and was verified to within experimental accuracy for the intermediate class of shock waves.

Development of Shock-Wave-Powered Actuators for High Speed Positioning

2011 ◽  
Vol 5 (6) ◽  
pp. 786-792 ◽  
Author(s):  
Akira Kotani ◽  
◽  
Toshiharu Tanaka ◽  
Atsushi Fujishiro ◽  
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
High Speed ◽  
Initial Conditions ◽  
Reflected Shock Wave ◽  
Compressive Wave ◽  
Reflected Shock ◽  
Temperature And Pressure ◽  
Driver Section ◽  
End Wall

A shock wave is a compressive wave which propagates at supersonic speed. A shock wave is generated by the emission of energy for a very short duration by high speed phenomena, such as explosions, discharges, collisions, high speed flights, etc. Shock tube experiments have played an important role in the field of high speed gas dynamics. A shock tube is usually divided by a diaphragm into a driver section and a driven section. Generally, the initial conditions of the driver and driven sections are high and low pressure, respectively. When the diaphragm breaks, a shock wave is generated in the driven section. The density, temperature and pressure of the gas behind the shock wave rise discontinuously. The shock wave arrives at the end wall of the tube, and a reflected shock wave is generated by the reflection from the wall. The quantities behind the reflected shock wave rise further. If the shock wave can be generated continuously without the diaphragm needing to be changed, this phenomenon could possibly be applied to an actuator having a piston that moves at high speed. In this study, equipment powered by a shock wave is produced, and its performance is examined. The results show that piston movement generated by a shock wave is faster than that which is not and that the piston speeds depend on the initial conditions. Also, the characteristic of the actuator powered by the shock wave is revealed.

scholarly journals Experimental investigation of shock waves in liquid helium I and II

1976 ◽  
Vol 75 (2) ◽  
pp. 373-383 ◽  
Author(s):  
John C. Cummings
Keyword(s):  
Shock Wave ◽  
Experimental Investigation ◽  
Shock Waves ◽  
Shock Tube ◽  
Liquid Helium ◽  
Initial Conditions ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Liquid Interface ◽  
Reflected Shock

The flow field produced by a shock wave reflecting from a helium gas-liquid interface was investigated using a cryogenic shock tube. Incident and reflected shock waves were observed in the gas; transmitted first- and second-sound shocks were observed in the liquid. Wave diagrams are constructed to compare the data with theoretical wave trajectories. Qualitative agreement between data and theory is shown. Quantitative differences between data and theory indicate a need for further analysis of both the gas-liquid interface and the propagation of nonlinear waves in liquid helium.This work was a first step in the experimental investigation of a complex non-equilibrium state. The results demonstrate clearly the usefulness of the cryogenic shock tube as a research tool. The well-controlled jump in temperature and pressure across the incident shock wave provides unique initial conditions for the study of dynamic phenomena in superfluid helium.

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