Shock Waves In Liquids Research Articles

An Experimental Study on Shock Waves in Liquid : The Generation of Shock Waves by an Impinging Piston and their Behavior

Onedimensional pressure waves (shock waves) were generated in a liquid (water) column contained in a vertical pipe by the impingement of a piston accelerated by compressed air. The waveforms obtained were sawtooth waves with peak pressures of 100-500kg/cm2 and widths of 1 to 2 msec. While waves in this pressure range were found to behave essentially as sound waves, the steepening of the wave front with originally a rise time of tens of micro-seconds to a discontinuity over a propagation distance of around 2 meters was observed, which was explainable in terms of the compressibility of the liquid. The density change across the wave front measured with the integrated schlieren technique was found to be proportional to the pressure change in accordance with the relation of adiabatic change of he medium. The motion of the piston following the impingement was observed by means of instantaneous photography, and a fine correspondence of the deceleration process with the generated waveform was evidenced. The displacement velocity of the liquid behind the wave front was also measured with a simple technique.

Laser-induced shock waves in liquids

High-speed schlieren photography of the interaction of a TEA CO2 laser pulse with the surface of absorbing liquids shows the formation of a complex shock structure in the liquid. The shock structure in liquids with different absorption coefficients at 10.6 μm is compared. In carbon tetrachloride a cylindrical wave is generated in the bulk of the liquid in addition to the hemispherical wave which is formed at the liquid surface. The cylindrical wave leads the hemispherical one, and this separation is interpreted as differential attenuation in the initial phase. This implies a shock velocity above the sound speed within the first 0.5 μs.

Laser-induced shock waves in liquids

The interaction of TEA-CO2-laser pulses with liquids has been investigated using shadowgraphy and high-speed pressure transducers. It is shown that the absorption coefficient of the liquid at the laser wavelength defines the geometry of the shock wave. Peak pressures in the kbar range have been observed.

Structure of shock waves in a liquid containing gas bubbles

The structure of a stationary shock wave in a liquid containing gas bubbles is investigated theoretically. For the description of such a two-phase mixture the two-velocity two-temperature model with two pressures is used [1], taking into consideration the small-scale frictions, the noncoincidence of the velocities, temperatures, and pressures of the phases, and the oscillations of the bubbles. The existence of shock waves having a discontinuity surface in front as well as of shock waves with continuous structure is shown. It is shown that unlike the two-phase mixtures of gas with drops or particles where the structure of the wave depends mainly on the interphase friction, in two-phase mixtures of a liquid with bubbles the behavior of the wave and its structure depends essentially on the interphase heat transfer. Wave characteristics, such as the wavelength of the pulsations, their damping decrement, do not have a monotonic dependence on the parameters governing the intensity of heat transfer and do not lie between the corresponding values for isothermic and adiabatic regimes of behavior of the bubbles. Shock waves in liquids with gas bubbles were investigated theoretically and experimentally in [3–7]. A detailed review of the work up to 1971 is given in [8].

An Experimental Study on Shock Waves in Liquid : The Generation of Shock Waves by an Impinging Piston and Their Behavior

An Experimental Study on Shock Waves in Liquid : The Generation of Shock Waves by an Impinging Piston and Their Behavior

Shock wave in a gas-liquid medium

The propagation of weak shock waves and the conditions for their existence in a gas-liquid medium are studied in [1]. The article [2] is devoted to an examination of powerful shock waves in liquids containing gas bubbles. The possibility of the existence in such a medium of a shock wave having an oscillatory pressure profile at the front is demonstrated in [3] based on the general results of nonlinear wave dynamics. It is shown in [4, 5] that a shock wave in a gas-liquid mixture actually has a profile having an oscillating pressure. The drawback of [3–5] is the necessity of postulating the existence of the shock waves. This is connected with the absence of a direct calculation of the dissipative effects in the fundamental equations. The present article is devoted to the theoretical and experimental study of the structure of a shock wave in a gas-liquid medium. It is shown, within the framework of a homogeneous biphasic model, that the structure of the shock wave can be studied on the basis of the Burgers-Korteweg-de Vries equation. The results of piezoelectric measurements of the pressure profile along the shock wave front agree qualitatively with the theoretical representations of the structure of the shock wave.

Laser Generated Thermoelastic Shock Waves in Liquid

The interactions of lasers with matter are manyfold. Among the important interactions is the generation of pressure waves by laser heating in an optically absorbing dye. The conversion of energy from transient laser heating to an acoustic wave is considered in detail in this paper. As a laser pulse enters an absorbing dye, energy is absorbed and converted into heat. Part of it will appear as elastic energy in the form of a pressure wave, due to very small expansion in the dye during the laser pulse.

One-Dimensional Flow of Liquids Containing Small Gas Bubbles

Early papers on the subject matter of this review, such as Mallock's (1910) Damping of Sound in Frothy Liquids or Minnaert's (1933) Musical Air Bubbles and the Sound of Running Water, were written out of interest in physical phenomena. In papers written during and after World War II this interest was mixed with motives of a more grim nature because it was sought to take advantage of the acoustical properties of bubbly liquids to control the sound produced by propellers, both of surface ships and sub­ merged ships. The literature on the subject deals therefore for a large part with theoretical and experimental studies of the various aspects of propaga­ tion of pressure waves of small amplitude in bubbly liquids. A major part of this review will be devoted to this topic, Sections 2-4. Apart from this, various schemes have been envisaged in which the dynamic properties of bubbly liquids could be profitably used in the design of devices to propel high-speed waterborne craft, such as hydrofoil and aircushion boats. This made it valuable to investigate the flow of bubbly liquids through Laval nozzles and similar configurations. This type of flow will be discussed in Section 5. In recent years research not directed by the need for data on acoustical properties has been carried out on waves in bubbly fluids beyond the acoustical regime, where disturbances to a given quiescent state are no longer of infinitesimal smallness. The effects of nonlinearity, dispersion, and dissipation, discussed in Section 6, lead as in other areas, such as those of plasma waves and water waves, to mathematical description by Burgers' equation and that of Korteweg and de Vries. Nonlinearity, dispersion, and dissipation cooperate in the formation of shock waves in bubbly liquids, the structure of which has been investigated to some extent, as reviewed in Section 6. The present review is restricted to flows described along the above lines. This means that bubbly flow forming the coolant of nuclear reactors is not included. There the bubbles are mostly large vapor bubbles and the interest is primarily in heat transfer.

High Speed Metal Forming Of Circular Disks AndCylindrical Tubes In A Liquid Shock Tube

High-speed metal forming with liquid shock waves, generated non-explosively, is a new field of study. The advantage of forming with liquid shock waves in a shock tube in comparison to explosive forming is better control and increased safety. This paper describes the experimental set-up of a liquid shock tube, discusses the operating cycle with respect to transformation of energy and presents the results of experiments performed with circular disks and cylindrical tubes. The deformation process of the disks and tubes during the impact of the liquid shock wave is investigated with a high-speed video camera. From the experiments the deformation velocities and the strain rates are determined.

On the structure of shock waves in liquid-bubble mixtures

The structure of shock waves in liquids containing gas bubbles is investigated theoretically. The mechanisms taken into account are the steepening of compression waves in the mixture by convection and the effects due to the motion of the bubbles with respect to the surrounding fluid. This relative motion, radial and translational, gives rise to dissipation and to dispersion caused by the inertia of the radial flow associated with an expanding or compressed bubble. For not too thick shocks the dissipation by radial motion around the bubbles dominates over the dissipation by relative translational motion, in mixtures with low gas content. The overall thickness of the shock appears to be determined by the dispersion effect. Dissipation, however, is necessary to permit a steady shock wave. It is shown that, analogous to undular bores, a stationary wave train may exist behind the shock wave.

Sound and Shock Waves in Liquids Containing Bubbles

The propagation of infinitesimal sound waves in a liquid containing gas bubbles is considered. Relative motion of gas bubbles and liquid is explicitly allowed for, and it is shown that a significant error in the speed of waves may arise if the relative motion and fluctuations of mass fraction are neglected. The structure of steady shock waves is also derived.

Лекционные демонстрации с ударной волной в жидкости

Лекционные демонстрации с ударной волной в жидкости

Kerr Cell Photography of High Speed Phenomena

Visible light photographs have been obtained of metal jets squirted from the lined conical cavities of high explosive charges. Since these jets travel through air at nearly meteoric velocities (7 to 12×105 cm/sec), their front ends are heated to incandescense and vaporized. The remainder of the jet is relatively nonluminous and is photographed by synchronizing a Kerr cell shutter (exposure time <1 μsec) and an exploding wire light source (peak intensity 4×108 candlepower) with the phenomenon. Schlieren type photography cannot be used because of the luminosity accompanying the phenomenon. Detail is obtained in the photographs by using a large lens with a seven-in. focal length. To maintain the effective aperture at f/4 requires a large Kerr cell which in turn requires a 25,000 volt pulse for its operation. The technique is used in studying the action of these jets on steel, water, glass, and Plexiglas. The technique is also used in studying the propagation of shock waves in solids and liquids when these phenomena are due to the action of the metal jets or to the more direct action of explosives.

MECHANISM OF DETONATION IN EXPLOSIVES

Results of photographic work on the detonation of high explosives are presented and discussed in their relationship to the hydrodynamic theory of detonation. The two most important properties of an explosive are its strength and its detonation velocity. Methods for determining these quantities are described. A moving film camera of the rotating drum type is especially useful in determining detonation velocity and in studying the nature of detonation. The photographic results, which are illustrated by a number of pictures, are helpful in demonstrating various elements of the theory. These photographs illustrate the nature of detonation waves in explosives and of shock waves in air. The duration of the detonation waves in nitroglycerin and blasting gelatin is less than one millionth of a second and the duration of the shock waves produced by these explosives in air is of the same order. The high temperature of shock waves which is predicted by theory is confirmed by the intense luminosity shown in photographs. The relatively low temperature predicted for shock waves in liquids is similarly confirmed by the absence of luminous shock waves in water. Photographs are included showing the propagation of detonation from one cartridge of blasting gelatin to another across air gaps and water gaps. In the latter case no visible shock wave is produced in the water and the highly luminous after‐burning is eliminated. Calculated values of the detonation velocity for nitroglycerin, blasting gelatin and 60% gelatin dynamite are in approximate agreement with the experimentally determined values. Calculations indicate that pressures in the detonation wave may run as high as 140,000 atmospheres and temperatures to 4300°C. The shape of the detonation wave front in a high velocity explosive like blasting gelatin is apparently planar whereas in low velocity explosives it is convex. The actual mechanism of energy propagation in detonation is not clearly understood out probably involves activation of the explosive at the detonation wave front by high velocity products of the detonation which are projected forward at speeds even greater than the detonation velocity.