Underwater Shock Wave Research Articles

Shock wave interaction with interfaces between materials having different acoustic impedances

We experimentally examined interaction of blast waves with water-air/air-water interfaces through high-speed-real-time visualization and measurement of pressure across the waves. The underwater shock wave, which was expected to reflect totally at the water-air interface, was observed transmitting a shock front to air. Transmission of a blast wave from air to water was also visualized and evaluated. Underwater shock waves are used in several medical/biological procedures, where such unforeseen transmissions can result in detriments. The details provide a guideline to evaluate blast wave transmissions, which can induce tissue and brain injuries. The results explain mechanisms behind blast-induced traumatic brain injury.

308 水中衝撃波を受けた微生物の死滅率に及ぼす固体微粒子の影響(大気・水環境保全・改善技術(3))

Ballast water is used to stabilize an empty ship on the open sea. It often contains various microorganisms such as plankton and bacteria, and causes serious damage to aquatic ecosystems where it is discharged. Ultra-high pressure underwater shock waves were applied to treatment those microorganisms. The imploding detonation of propane-oxygen mixture was used to generate underwater shock wave in sample holder. The authors investigated imploding detonation wave in approximately cone-shaped combustion chamber having maximum inner diameter of 60 mm. Solid particles were added in sample water to simulate real seawater. As a consequence, mortality rate was increased by the addition of large solid particles. However mortality rate was reduced with increasing concentration of small solid particles. This is considered to be due to the damping effect of underwater shock wave caused by particles.

The Effect of Underwater Shock Waves on Steam Distillation of <i>Alpinia zerumbet</i> leaves

(Pers.) B.L. Burtt & R.M. Smith is an aromatic plant, distributed widely in the Ryukyu Islands, Japan. It has been extensively studied because its essential oil has a variety of biological functionalities. Underwater shock waves consist of instantaneous high pressures that penetrate entire plant cells and selectively destroy the cell walls of leaves and stems by spalling destruction. Therefore, it is expected that exposing leaves to shock waves as a preprocessing step draws more effective extraction of essential oil by subsequent steam distillation. In this study, we prepared

826 気泡崩壊により発生する水中衝撃波の光学的手法による圧力測定の試み(GS-5 気泡)

826 気泡崩壊により発生する水中衝撃波の光学的手法による圧力測定の試み(GS-5 気泡)

H142 収束爆轟駆動水中衝撃波の最高圧力に及ぼす最終収束半径の影響

It was shown by theoretical and experimental studies that high temperature and high pressure state is provided in the converging center by converging shock wave or imploding detonation. In particular, the imploding detonation can implode more effectively than the case of the shock wave. The authors examined the microorganism treatment technique using ultra-high pressure underwater shock waves in a steel pipe by the gas imploding detonation until now. The authors tried to confirm the effect of underwater shock wave generation by change minimum converging radial distance of imploding detonation, equivalence ratio and concentration of the nitrogen as diluent. As a result, effect of the equivalence ratio was small in comparison with the change in the minimum converging radial distance. Therefore, influence of diluent addition was different each minimum converging radial distance.

H143 収束爆轟駆動水中衝撃波を利用したアオコの死滅処理技術の開発

H143 収束爆轟駆動水中衝撃波を利用したアオコの死滅処理技術の開発

An Analytical Method for the Response of Coated Plates Subjected to One-Dimensional Underwater Weak Shock Wave

An analytical method based on the wave theory is proposed to calculate the pressure at the interfaces of coated plate subjected to underwater weak shock wave. The method is carried out to give analytical results by summing up the pressure increment, which can be calculated analytically, in time sequence. The results are in very good agreement with the finite element (FE) predictions for the coating case and Taylor’s results for the noncoating case, which validate the method that is suitable for underwater weak shock problem. On the other hand, Taylor’s results for the coating case are invalid, which indicates a potential application field for the method. The extension of the analytical method to q-layer systems and dissipation case is also outlined.

309 気体収束爆轟型液体殺菌装置の開発(大気・水環境保全・改善技術(3))

The imploding detonation of a propane-oxygen mixture was used to generate underwater shock waves in a sample holder. We used the three kinds of experimental apparatuses whose the inner diameters of main combustion chamber are 60 mm, 150 mm, and 400 mm. The experimental results show that maximum pressure at the implosion center was 150 to 18000 times higher than the initial pressure. Although the maximum pressure in the exit of a sample holder changes with the sizes of experimental apparatus, pressure increase speed is almost constant. We found that the peak pressure in the end of a sample holder can be increased by expansion of the size of the main combustion chamber, and that we can perform scale-up and automatic operation of sterilization equipment.

Explosion Power and Pressure Desensitization Resisting Property of Emulsion Explosives Sensitized by MgH2

Due to low detonation power and pressure desensitization problems that traditional emulsion explosives encounter in utilization, a hydrogen-based emulsion explosives was devised. This type of emulsion explosives is sensitized by hydrogen-containing material MgH2, and MgH2 plays a double role as a sensitizer and an energetic material in emulsion explosives. Underwater explosion experiments and shock wave desensitization experiments show that an MgH2 emulsion explosives has excellent detonation characteristics and is resistant to pressure desensitization. The pressure desensitization–resistant mechanism of MgH2 emulsion explosives was investigated using scanning electron microscopy.

Research of High-Power Underwater Explosive Based on Analysis of Underwater Energy

In this paper,by researching the underwater energy output structure of explosion and improving the technical method to enhance the energy of underwater high-power explosive,a new type of underwater high-power PBX explosive was developed. This type of PBX,of which the underwater shock wave energy was 1.75 TNT equivalent and its bubble energy was 2.41 TNT equivalent,was suitable for the main charge of underwater weapon warhead and its energy archived the domestic leading level.

Simulation of damage–permeability coupling for mortar under dynamic loads

SUMMARYThe results reported in this paper deal with the simulation of damage in cohesive geomaterials such as rocks or concrete subjected to dynamic loads. The practical objective is to stimulate the production of tight gas reservoirs with a technique that is an alternative to hydraulic fracturing. The principle is that when subjected to dynamic loads, cohesive materials such as concrete, rocks or ceramics exhibit distributed micro‐cracking as opposed to localised cracking observed under static loads. Hence, a low permeability rock containing gas trapped into occluded pores can be fragmented with the help of dynamic loads, and gas can be extracted in a much more efficient way compared with hydraulic fracturing, where only large macro cracks are formed with very few connections between occluded pores. At the stage of laboratory development of this technique, compressive underwater shock waves have been used to increase the intrinsic permeability of concrete specimens. In a previous study, pressure waves generated by pulsed arc electrohydraulic discharges in water were used in order to induce micro‐cracking and an increase of average permeability of concrete hollow cylinders subjected to confinement stresses (equivalent to geostatic stresses). We discuss here a 3‐D anisotropic constitutive model aimed at describing the dynamic response of these specimens. It is based on rate‐dependent continuum damage constitutive relations. Crack closure effects and damage‐induced anisotropy are included in the model. The directional growth of damage is related to the directional growth of material intrinsic permeability. Numerical simulations of damage induced by shock waves show good agreement with the experiments for various confinement levels of the specimens. Copyright © 2013 John Wiley & Sons, Ltd.

Study of underwater shock waves and cavitation bubbles generated by pulsed electric discharges

The paper reports on generation of controllable underwater shock waves through the use of a magnetic pulsed compression circuit as the power source of underwater spark discharge to aid in improving accuracy and safety in medical applications. In the present work, we were able to widely change the peak pulsed voltages by the magnetic pulsed compression circuit. Sensitivity of underwater shock wave pressure to peak voltage variation was obtained near the electrodes in the 200 to 400 MPa range with voltage amplitudes from 10 to 18 kV. Effects of pulsed electric discharge parameters such as the voltage amplitude and pulse duration on characteristics of cavitation bubbles and shock waves were observed and analyzed. Visualization results and image analysis allowed evaluation of radii and collapse times of cavitation bubbles and their generated shock waves pressures. Pressures of underwater shock waves were also measured by a fiber optic probe hydrophone and were compared with the visualization analyses results.

Creation of Emulsion Fuel Using Underwater Shock Wave

Generally, emulsion fuel means mix of fuel and water. But normally, these two kinds of liquid easily separate. In this study, underwater shock wave is used to mix these liquid. Purpose of this study is to create emulsion fuel using underwater shock wave. That fuel is needed not to separate. In our experiment, samples were prepared which consists of diesel fuel, water, and other liquid which might help to make emulsification between water and diesel oil. These liquid are packed into polycarbonate bottles. And underwater shock wave is hit to these samples. Detonating fuse and electric detonator are used to make shock wave. The underwater shock wave is hit to each sample for 5 times. After this experiment, these samples are observed to see if these samples separate again or not. Results shows that emulsion fuel we made separated as time passed. In the future study, it is needed that establishment of the way to control those separation.

Study on Behavior of Underwater Shock Wave in Enclosed Vessel

We are developing the food processing system by using the underwater shock wave. The effect of the underwater shock wave on the pressure in the vessel is the important factor for food processing system in this research. The purpose of this study is to research the behavior of the underwater shock wave in the enclosed vessel to investigate the influence of the contour of the elliptical vessel on the pressure. In this research, we used the elliptical shape for the vessel and the explosive was used to generate the shock wave. Numerical calculation was carried out by using LS-DYNA. The ratio of the length of the major axis to minor axis of the elliptical were changed, as a main parameter. As a result, it was found that underwater shock wave was generated and propageated in the elliptical vessel following the explosion. The underwater shock wave was coverged at the focal point. At the same time, the pressure was increased by the coverged underwater shock wave at the focal point in the all elliptical vessels. It was also found that the peak pressure at the focal point was determined by the contour of the elliptical vessel.

Development and Improvement of the Experimental Apparatus Using the Underwater Shock Wave

The underwater shock wave has been studied in the various fields. The application of this method can be used for a molding machining, a welding and an embossing in the metal processing [. Moreover, this processing method can be used for a pulverizing, a softening, and a sterilization in the food processing. The aim of this research is to make the rice powder using by the underwater shock wave without generating of heat [. Although the underwater shock wave is generated using an explosive, the handling of the explosive is extremely accompanied by danger. Therefore, we developed the electric discharging device made to generate the underwater shock wave. It is easier to carry on the experiment using this device than the experiment of an explosive. We developed a pressure vessel for generating the underwater shock wave in various fields. The developed pressure vessel has been improved by our research group. The pressure vessel made to generate the shock wave is manufactured from a new concept, and the coaxial cable is used for wiring of the device.

Experimental Study on Food Seasoning Treatment by High Voltage Electrical Discharge with Shock Wave Food Processor

In recent years, a method of food processing using underwater shock wave has been investigated. The underwater shock wave is generated by high voltage and large current gap discharge in water, and it is used for food processing in the present investigation. When the underwater shock wave is loaded on the food, the food cells are momentarily broken. Therefore, the food becomes soft, and possible to squeeze water easily. Also, seasonings can be penetrated inside of the food. The improvement of absorbing seasonings for the shock processed foods mainly on Japanese radish is reported in this paper.

Underwater Shock Wave Research Applied to Therapeutic Device Developments

The chronological development of underwater shock wave research performed at the Shock Wave Research Center of the Institute of Fluid Science at the Tohoku University is presented. Firstly, the generation of planar underwater shock waves in shock tubes and their visualization by using the conventional shadowgraph and schlieren methods are described. Secondly, the generation of spherical underwater shock waves by exploding lead azide pellets weighing from several tens of micrograms to 100 mg, that were ignited by irradiating with a Q-switched laser beam, and their visualization by using double exposure holographic interferometry are presented. The initiation, propagation, refl ection, focusing of underwater shock waves, and their interaction with various interfaces, in particular, with air bubbles, are visualized quantitatively. Based on such a fundamental underwater shock wave research, collaboration with the School of Medicine at the Tohoku University was started for developing a shock wave assisted therapeutic device, which was named an extracorporeal shock wave lithotripter (ESWL). Miniature shock waves created by irradiation with Q-switched HO:YAG laser beams are studied, as applied to damaged dysfunctional nerve cells in the myocardium in a precisely controlled manner, and are effectively used to design a catheter for treating arrhythmia.

An Investigation on Deburring Technology Using Concentrated Underwater Shock Wave

When a few branched holes are made in order to cross a main hole at right angle, burrs are produced on the sidewall of the main hole at end of each branched hole. The principle of the process is as follows. After the specimen of which all holes are closed by using sealing tape is submerged, explosive set at the position a little apart from the entrance of the main hole is detonated. As soon as the generated underwater shock wave is arrived at the entrance of the main hole, the sealing tape is broken and the water stream with very high velocity flows into the main hole. The deburring is performed by the action of the water stream with very high velocity. The deburring is sufficiently succeeded in most case. When the main hole is closed, however, the deburring could not be succeeded at the branched hole very near closed position. In order to improve the insufficiency of the process, we designed new equipment in order that underwater shock wave may be concentrated at the entrance of main hole and the water stream with very high velocity, which is caused by the shock wave, may flow along sidewall on which burr is generated. In the present report, we propose the new method and give full account of the experimental results for deburring obtained by using the equipment.

Pressure Measurements and Numerical Simulation of Underwater Shock Wave for Food Processing

This study attempts to clarify underwater shock waves using a food container designed for food processing. The underwater shock wave is driven by a spark or wire explosion from a high-capacity condenser bank. Since the applied pressure must be known to control the experimental conditions, a numerical simulation was conducted and the results were compared with measurements using an elastic bar placed in the water.

Food Processing Trials Using Underwater Shock Wave by Electrical Discharge

We propose a new method for the efficient decompression of frozen food under high dynamic pressure. Two experiments are conducted on an ice block containing peeled shrimp: wire explosion and underwater shock wave. In these experiments, the ice is finely crushed, while the frozen peeled shrimps retain their original shape and can be efficiently extracted. Since ice crushing is performed momentarily, the defrosting time is significantly shorter than that in traditional thawing techniques, such as melting in running water or cold-water soaking. This new method could increase the efficiency of food production processes.