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The present work aimed to investigate the effect of underwater shock wave (USW) on palm oil yield. Palm fruits were prepared and treated by applying USW before oil extraction. Strong USWs were generated by discharging high electric voltage into water, and varying the supplied voltage in the range of 2 - 10 kV. Following USW treatment, two methods of palm oil extraction namely screw-press and solvent extraction were used to determine the oil yield. Oil yield extraction and microstructure morphology of palm mesocarp were also investigated. It was found that at 10 kV of the USW treatment, the highest yield of palm oil extraction through screw-press method was 66.35%, while the solvent extraction method yielded 70.38%, which were 3.1 and 6.3% improvement, respectively, as compared to the untreated extraction. Microstructure analysis by scanning electron microscope (SEM) of palm mesocarp showed that the oil cells had significant cracks on the surface following treatment with USW. This confirmed that the application of USW was effective in increasing palm oil yield extraction. With a reliable strength and repetition of the treatment, USW treatment is promising for practical application in the palm oil industry and also other plant oil extraction.

Traumatic injury caused by explosive or blast events is traditionally divided into four mechanisms: primary, secondary, tertiary, and quaternary blast injury. The mechanisms of blast-induced traumatic brain injury (bTBI) are biomechanically distinct and can be modeled in both in vivo and in vitro systems. The primary bTBI injury mechanism is associated with the response of brain tissue to the initial blast wave. Among the four mechanisms of bTBI, there is a remarkable lack of information regarding the mechanism of primary bTBI. On the other hand, 30 years of research on the medical application of shock waves (SWs) has given us insight into the mechanisms of tissue and cellular damage in bTBI, including both air-mediated and underwater SW sources. From a basic physics perspective, the typical blast wave consists of a lead SW followed by shock-accelerated flow. The resultant tissue injury includes several features observed in primary bTBI, such as hemorrhage, edema, pseudo-aneurysm formation, vasoconstriction, and induction of apoptosis. These are well-described pathological findings within the SW literature. Acoustic impedance mismatch, penetration of tissue by shock/bubble interaction, geometry of the skull, shear stress, tensile stress, and subsequent cavitation formation are all important factors in determining the extent of SW-induced tissue and cellular injury. In addition, neuropsychiatric aspects of blast events need to be taken into account, as evidenced by reports of comorbidity and of some similar symptoms between physical injury resulting in bTBI and the psychiatric sequelae of post-traumatic stress. Research into blast injury biophysics is important to elucidate specific pathophysiologic mechanisms of blast injury, which enable accurate differential diagnosis, as well as development of effective treatments. Herein we describe the requirements for an adequate experimental setup when investigating blast-induced tissue and cellular injury; review SW physics, research, and the importance of engineering validation (visualization/pressure measurement/numerical simulation); and, based upon our findings of SW-induced injury, discuss the potential underlying mechanisms of primary bTBI.

Aims Although the radiofrequency catheter ablation (RFCA) is widely used for the treatment of tachyarrhythmias, it has three fundamental weaknesses as a thermal ablation system, including a limited lesion depth, myoendocardial injury linking to thromboembolism, and prolonged inflammation followed by subsequent recurrences. In order to overcome these limitations, we have been developing a shock wave (SW) catheter ablation (SWCA) system as a novel non-thermal therapy. In the present study, we validated our new SWCA system with increased SW intensity. Methods and results In a total of 36 pigs, we applied our new SWCA to ventricular muscle in vivo for the following protocols. (i) Epicardial approach (n = 17): The lesion depth achieved by the SWCA from the epicardium was examined. High intensity SW achieved 5.2 ± 0.9 mm lesions (35 applications), where there was a strong correlation between SW intensity and lesion depth (R = 0.80, P

Background Although radiofrequency catheter ablation is the current state‐of‐the‐art treatment for ventricular tachyarrhythmias, it has limited success for several reasons, including insufficient lesion depth, prolonged inflammation with subsequent recurrence, and thromboembolisms due to myoendocardial thermal injury. Because shock waves can be applied to deep lesions without heat, we have been developing a shock‐wave catheter ablation ( SWCA ) system to overcome these fundamental limitations of radiofrequency catheter ablation. In this study, we evaluated the efficacy and safety of our SWCA system for clinical application to treat ventricular tachyarrhythmia. Methods and Results In 33 pigs, we examined SWCA in vivo for the following 4 protocols. First, in an epicardial substrate model (n=8), endocardial SWCA significantly decreased the sensing threshold (pre‐ versus postablation: 11.4±3.8 versus 6.8±3.6 mV ; P P SWCA of the border zone of the infarcted lesion was as effective as ablation of the normal myocardium. Third, in a coronary artery application model (n=10), direct application of shock waves to the epicardial coronary arteries caused no adverse effects in either the acute or chronic phase. Fourth, with an epicardial approach (n=8), we found that 90 shots per site provided an ideal therapeutic condition to create deep lesions with less superficial damage. Conclusions These results indicate that our new SWCA system is effective and safe for treatment of ventricular tachyarrhythmias with deep arrhythmogenic substrates.

Shock wave mitigation in air is one of the important research topics of the shock-wave research. Strong or moderate shock waves can be attenuated in a relatively straightforward manner, whereas weak shock waves take a longer process to be attenuated to sound waves. In this chapter experimental results of shock wave mitigations are presented.

Gabor (1948), for the first time, presented the concept holography. In 1971, the Nobel Prize in physics was awarded on him for his invention of holography, which opened a new era in the flow visualization. This was a long time before the advent of the lasers. Encouraged by the development of lasers, Light beams are characterized by their amplitude and phase angle. Leith and Upatnieks (1962) developed off-axis holography in which object and reference beams, OB and RB, illuminate on a holographic film with an off-axial direction and became a basis of modern holographic interferometry.

In 1980, the shock wave laboratory received a license that permitted to used a small amount of explosives in scientific experiments.

A transition from regular to Mach reflection of shock waves over wedges was investigated experimentally and numerically. Experimental and numerical results showed good agreements on trajectory of shock triple point. It was demonstrated that the influence of boundary layer is very significant on the transition condition.

In 1981, Professor M. Kuwahara of the Department of Urology, School of Medicine, Tohoku University invited us to develop a prototype lithotripter using micro explosions. Then the collaboration started applying results of the basic experiments to design a lithotripsy for clinical use.

The two-dimensional shock wave focusing is divided into two patterns: the reflection from concave walls and; the convergence of curved incident shock waves, which is called implosion. This is a reverse process of an explosion.

When a shock wave is reflected from a steep wedge, the reflected patter of the incident shock wave, or in short IS, forms a V shaped wave pattern. This pattern is similar to a sound wave reflection from a plane wall and hence is named as a “regular reflection”, and in short RR. A head-on-collision of a shock wave with a plane wall is an extreme case of the RR.

The paper reviews the author’s shock wave research inspired by Professor I. I Glass of UTIAS. Firstly, a preliminary underwater shock wave research by using a shock tube is briefly described. Secondly, small-scale underwater explosions of primary explosives visualized by means of double exposure holographic interferometry. Results of experiments performed by the refurbished hypervelocity shock tube donated from UTIAS to IFS in 1994 are presented.

Liquids are less compressible than gases. The compressibility is the measure of volume change when compressed by pressure.

In the 18th ISSW, a poster session regarding diffraction of shock wave of Ms = 1.50 in air at a 90° sharp corner was organized. Results of 16 numerical simulations and 3 visualizations were presented.

Shock wave interactions with cylinders and other bodies are one of the fundamental topics of shock-dynamics. In this chapter results of flow visualizations over these body are presented.

The high-speed liquid (water) jet has distinctive characteristics in surgical applications, such as tissue dissection without thermal damage and small blood vessel preservation, that make it advantageous over more conventional instruments. The continuous pressurized jet has been used since the first medical application of water jets to liver surgery in the 1980s, but exhibited drawbacks partly related to the excess water supply required and unsuitability for application to microsurgical instruments intended for deep, narrow lesions (endoscopic instrumentation and catheters) due to limitations in miniaturization of the device. To solve these issues, we initiated work on the pulsed micro-liquid jet. The idea of the pulsed micro-liquid jet originated from the observation of tissue damage by shock/bubble interactions during extracorporeal shock wave lithotripsy and evolved into experimental application for recanalization of cerebral embolisms in the 1990s. The original method of generating the liquid jet was based on air bubble formation and microexplosives as the shock wave source, and as such could not be applied clinically. The air bubble was replaced by a holmium:yttrium-aluminum-garnet (Ho:YAG) laser-induced bubble. Finally, the system was simplified and the liquid jet was generated via irradiation from the Ho:YAG laser within a liquid-filled tubular structure. A series of investigations revealed that this pulsed laser-induced liquid jet (LILJ) system has equivalent dissection and blood vessel preservation characteristics, but the amount of liquid usage has been reduced to less than 2 $$\upmu $$ l per shot and can easily be incorporated into microsurgical, endoscopic, and catheter devices. As a first step in human clinical studies, we have applied the LILJ system for the treatment of skull base tumors through the transsphenoidal approach in 9 patients (7 pituitary adenomas and 2 chordomas), supratentorial glioma (all high grade glioma) in 8 patients, including one with fine perforating vessel involvement, and cerebrovascular disease (1 arteriovenous malformation and 2 intracerebral hemorrhages) in 3 patients. Precise dissection and mass reduction of the tumor were obtained in all tumor cases except for one chordoma with significant fibrosis. Small arteries down to 100 $$\upmu \hbox {m}$$ were preserved, allowing subsequent microsurgical devascularization. Veins were also preserved occasionally. The arachnoid membrane and the tumor capsule were resistant to the LILJ except for one case with prolonged exposure. No complications related to use of the LILJ system were observed. No disturbance of the surgical field by splashing, aerosol, or dissemination of pathological tissue occurred with placement of the optimal suction system. The Ho:YAG LILJ system enhances the advantages of commercialized pressure-driven continuous liquid jet instrumentation in terms of small vessel preservation and accessibility in confined spaces for minimally invasive neurosurgery, and solves some of the drawbacks involved with excessive liquid use and size.

A robust blast inhibiting bin is the most often used device for damage blast effects suppression. In particular, a top open cylindrical bin significantly reduces a fragmentation effect resulted from a detonation of an explosive device placed inside the bin. However, reduction of blast wave overpressure and impulse by such cylindrical bins is not sufficient [1] . A reasonable alternative to endless increase of height and thickness of robust blast inhibiting bins is a development of destructible inhibitors having no solid elements in their structure and, therefore, excluding secondary fragmentation. So, the family of “Fountain” inhibitors [2] , [3] localizes and suppresses damaging blast effects due to multiphase working system. The present study is analyzing data obtained in testing of prototypes of new combined inhibitors. Their structure combines robust elements (bottoms, side surfaces) with elements responsible for blast loads reduction due to multi-phase working system (top and low transverse embeddings) and fairings impeding wave propagation in undesirable directions.

For a medical application of shock waves, extracorporeal shock wave lithotripter (ESWL) has been established.

This is a summary of shock tube experiments performed at the Tohoku University from 1975 to 2005. Critical transition angles of reflected shock waves over concave and convex walls of radii from 20 to 300 mm were experimentally obtained and compared with the numerical simulation based on the Navier–Stokes equations. The experimental critical transition angles varied with the radii of curved walls and strongly affected by the presence of the boundary layer developing along curved walls. The effects of critical transition on shock wave dynamic, shock wave reflection from roughened wedges, double wedges, and shock focusing from curved walls were presented.

Results of optical flow visualizations of underwater shock waves performed in the Shock Wave Research Center of the Institute of Fluid Science in Tohoku University are presented. Underwater shock waves generated in ultrasound oscillations, underwater shock waves in two-phase shock tube flows, spherical shock waves in small scale underwater explosions, their interaction with gas bubbles and interfaces, and their reflection and focusing are visualized by single and double exposure holographic interferometry. Time resolved high-speed imaging revealed the luminous emission from a contracting gas bubble during shock/bubble interactions. It is concluded that double exposure holographic interferometry can be very effective for quantitative observation of underwater shock waves, and that high-speed time resolved imaging can be useful for the underwater shock wave research.

The propagation of relatively high-pressure and temperature exhaust gases discharged from automobile engine cylinders along exhaust pipes coalesced into weak shock waves, which eventually became sources of exhaust gas noises. The mitigation of these weak shock waves is one of the practical applications of shock wave research. The chapter describes the summary of continuous experimental studies firstly to verify the presence of weak shock waves in exhaust gas pipe lines, secondly the parametric shock tube experiment, by using double exposure holographic interferometry, of the mitigation of weak shock waves, and lastly the application of results to the design of prototype engine silencers and mufflers. The project has been performed by the collaboration between the Fuji Heavy Industry and the Institute of Fluid Science, Tohoku University.

Results of experiments investigating shock wave reflections from wedges having sawtooth roughness of 0.1 mm, 0.2 mm, 0.8 mm, and 2.0 mm are presented. Observations based on direct shadowgraph diagnostic revealed that for wedges whose inclination angle was close to the critical transition angle, the foot of the incident shock interacted locally with the sawtooth steps and merged with the part of shock waves reflected from the sawtooth walls. This trend was observed for all the sawtooth wedges.

This chapter summarized results of experiments performed for many years and eventually we reached a conclusion. A stationary Mach reflection is a typical reflection pattern that exists in steady supersonic flows, whereas a similar reflection pattern appears over a double wedge and is temporally maintained. The consisted presence of the stationary MR in shock tube flows contradicts the self-similarity of the shock tube flows. The chapter discusses experimentally whether or not the stationary Mach reflection can exist over a double wedge in shock tube flows.

The current paper discusses the shock standoff distance over spheres in unsteady flows. In a ballistic range, spherical projectiles were launched into atmospheric air for wide transonic ranges of projectile Mach numbers. We visualized shock standoff distances of 40 mm diameter spheres with double-exposure holographic interferometry and those of 10 mm diameter spheres with direct shadowgraph by using a high-speed video camera. It was confirmed that shock standoff distances tend to increase with reducing the projectile Mach number. We also confirmed that the bow shocks exist even in front of the subsonic spheres, and their detachment distances increase with decreasing the projectile speeds to low subsonic ones.

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.

This paper describes a preliminary investigation of the characteristics of high-speed water jets injected into water from an orifice. The high-speed jets were generated by the impact of a projectile launched by a horizontal single-stage powder gun and submerged in a water test chamber. The ensuing impact-driven high-speed water jets in the water were visualized by the shadowgraph technique, and the images were recorded by a high-speed digital video camera. The processes following such jet injection into water, the jet-induced shock waves, shock wave propagation, the bubble behavior, bubble collapse-induced rebound shock waves and bubble cloud re-generation were observed. Peak over-pressures of about 24 and 35 GPa measured by a Polyvinylidence difluoride (PVDF) piezoelectric film pressure sensor were generated by the jet impingement and the bubble impingement, respectively. The peak over-pressure was found to decrease exponentially as the stand-off distance between the PVDF pressure sensor and the nozzle exit increases.

Background and Aim A current drawback of endoscopic submucosal dissection (ESD) for early-stage gastrointestinal tumors is the lack of instruments that can safely assist with this procedure. We have developed a pulsed jet device that can be incorporated into a gastrointestinal endoscope. Here, we investigated the mechanical profile of the pulsed jet device and demonstrated the usefulness of this instrument in esophageal ESD in swine. Methods The device comprises a 5-Fr catheter, a 14-mm long stainless steel tube for generating the pulsed water jet, a nozzle and an optical quartz fiber. The pulsed water jet was generated at pulse rates of 3 Hz by irradiating the physiological saline (4°C) within the stainless steel tube with an holmium-doped yttrium-aluminum-garnet (Ho:YAG) laser at 1.1 J/pulse. Mechanical characteristics were evaluated using a force meter. The device was used only for the part of submucosal dissection in the swine ESD model. Tissues removed using the pulsed jet device and a conventional electrocautery device, and the esophagus, were histologically examined to assess thermal damage. Results The peak impact force was observed at a stand-off distance of 40 mm (1.1 J/pulse). ESD using the pulsed jet device was successful, as the tissue specimens showed precise dissection of the submucosal layer. The extent of thermal injury was significantly lower in the dissected bed using the pulsed jet device. Conclusion The results showed that the present endoscopic pulsed jet system is a useful alternative for a safe ESD with minimum tissue injury.

The initiation and the propagation of detonation waves in a hemispherical chamber and the imploding shock waves that are the reflected detonation waves at the chamber wall are numerically investigated. The effects of the boundary layer and the non-uniformity of the flow field induced by the detonation wave on the imploding shock stability are examined. It is found that the effect of the boundary layer separation on the chamber wall has the strongest effect on the implosion focus.

Carbon fiber reinforced plastic composite materials have unique mechanical properties and could substitute aluminum alloys used in harsh environments. We performed high-speed impact experiments to study carbon fiber reinforced plastic fracture behavior at cryogenic temperatures for two specimens of different laminated constitution. The effect of temperature, impact velocity, and layered composition on the fracture behavior of carbon fiber reinforced plastic was examined. Perforation hole-sizes and shapes, as well as damaged regions on the specimens varied systematically depending on layered compositions. We found that carbon fiber reinforced plastic layered composition played an important role and damage regions were controllable by manipulating carbon fiber reinforced plastic layered compositions.

High-speed liquid jets have been applied to many fields of engineering, science and medicine. It is therefore of benefit to all these areas to investigate their characteristics by modern and inexpensive methods using a computational fluid dynamics (CFD) technique. Previously, high-speed liquid jets have been studied experimentally using a momentum exchange method, called the “impact driven method (IDM)”, by which the impact of a high-velocity projectile on the liquid package contained in the nozzle cavity produced the jet. The shock pulse reflections in the cavity caused by the impact then drove a multiple pulsed jet from the nozzle exit. In this study, a two-fluid simulation consisting of liquid and air can be successfully calculated by using a two-phase flow mixture model and a moving mesh for the projectile motion. The CFD results show good agreement to the results of previous experimental studies, both quantitatively and qualitatively. For the first time, the wave propagation within the liquid in the nozzle has been captured and analyzed, thereby demonstrating the dynamic characteristics of multiple pulsed high-speed liquid jets initiated by the IDM. This provides a breakthrough in the simulation of the supersonic injection of a liquid into air by using a well-known and user-friendly CFD software. It is useful fundamental knowledge for future studies of high-speed injection with applications in all its related fields.

This study is an investigation into the effects of temperature and pressure within a test chamber on the dynamic characteristics of injected supersonic diesel fuel jets. These jets were generated by the impact of a projectile driven by a horizontal single stage powder gun. A high speed video camera and a shadowgraph optical system were used to capture their dynamic characteristics. The test chamber had controlled air conditions of temperature and pressure up to 150 °C and 8.2 bar, respectively. It was found experimentally that, at the highest temperature, a maximum jet velocity of around 1,500 m/s was obtained. At this temperature, a narrow pointed jet appeared while at the highest pressure, a thick, blunt headed jet was obtained. Strong shock waves were generated in both cases at the jet head. For analytical prediction, equations of jet tip velocity and penetration from the work of Dent and of Hiroyasu were employed to describe the dynamic characteristics of the experiments at a standard condition of 1 bar, 30 °C. These analytical predictions show reasonable agreement to the experimental results, the experimental trend differing in slope because of the effect of the pressure, density fluctuation of the injection and the shock wave phenomena occurring during the jet generation process.

In the present paper, numerical measurements of turbulent length scales are performed by solving Reynolds-averaged Navier–Stokes equations with k–e turbulence model. The aim of the simulations is to investigate turbulence micro-scales variations as well as energy dissipation due to interaction of the turbulent flow with the shock wave. All turbulent properties are measured during the compression by the reflected shock wave on the turbulent field and it is observed that the turbulent length scales decrease in interaction of the shock wave with the turbulent field. The amplification of turbulent velocity length scale and the turbulent dissipative-length scale depend on the shock wave strength and the shock induced flow fields during interaction. The amplification of turbulent velocity length scale and the turbulent dissipative-length scale in interaction of the shock wave with subsonic flow field is higher as compare to the amplification in interaction of the shock wave with supersonic flow field. After the shock/turbulence interaction, the turbulent kinetic energy dissipation rate decreases for all types of flow fields behind the incident shock wave.

The three-dimensional (3D) shock wave reflections over two perpendicularly intersecting wedges are numerically studied in this paper, using the finite volume method which is based on the MUSCL-Hancock interpolation technique and self-adaptive unstructured mesh. Two kinds of 3D Mach stem structures are demonstrated by the numerical simulations for different shock Mach numbers and wedge angles. A four-shock or three-shock wave configuration appears in the vicinity of the corner of the wedges.

Accepted: 2011-03-03, 資料番号: SA1002878000

Traumatic brain injury caused by explosive or blast events is traditionally divided into four phases: primary, secondary, tertiary, and quaternary blast injury. These phases of blast-induced traumatic brain injury (bTBI) are biomechanically distinct and can be modeled in both in vivo and in vitro systems. The primary bTBI injury phase represents the response of brain tissue to the initial blast wave. Among the four phases of bTBI, there is a remarkable paucity of information about the cause of primary bTBI. On the other hand, 30 years of research on the medical application of shockwaves (SW) has given us insight into the mechanisms of tissue and cellular damage in bTBI, including both air-mediated and underwater SW sources. From a basic physics perspective, the typical blast wave consists of a lead SW followed by supersonic flow. The resultant tissue injury includes several features observed in bTBI, such as hemorrhage, edema, pseudoaneurysm formation, vasoconstriction, and induction of apoptosis. These are well-described pathological findings within the SW literature. Acoustic impedance mismatch, penetration of tissue by shock/bubble interaction, geometry of the skull, shear stress, tensile stress, and subsequent cavitation formation, are all important factors in determining the extent of SW-induced tissue and cellular injury. Herein we describe the requirements for the adequate experimental set-up when investigating blast-induced tissue and cellular injury; review SW physics, research, and the importance of engineering validation (visualization/pressure measurement/numerical simulation); and, based upon our findings of SW-induced injury, discuss the potential underlying mechanisms of primary bTBI.

The shock stand-off distance of a spherical model flying with transonic speeds is determined through numerical simulations. The model decelerates due to drag forces caused by the pressure and viscous shear stress at the model surface. Two-dimensional axisymmetric numerical codes with numerical grids fixed to the flying spherical model are used in the simulations. Numerically determined shock stand-off distances are compared with experimental data obtained in a previous study as well as with those obtained in our ballistic-range experiments. The numerical results and the experimental data are found to be in good agreement. In addition, the time-dependent shock stand-off distance of a decelerating model is investigated.

This paper reports the summary of experiments performed to successive generate small-scale underwater shock waves by means of shock-induced collapse of microbubbles confined in a narrow gap. The project is motivated to develop a method for efficient inactivation of marine bacteria contained in ship ballast water by high impulsive pressure loading. The shock wave–air bubbles interaction was visualized by shadowgraph; the images were recorded by ImaCon200, and simultaneous pressure measurements were performed by using an optical fiber pressure transducer with higher temporal resolution. Attaching small air bubbles on a single nylon fiber and placing it in a confined space, we demonstrated sequential generation of impulsive high pressures at the successive collapses of small bubbles at incident and reflected shock loadings. The values of the very short impulsive pressures that occurred repeatedly for a relatively long term are found high enough to inactivate marine bacteria.

At the event of the atomic bomb dropped in Hiroshima, Danbara district which is located behind Mount Hiji approximately 2.3 km distant from the center of explosion, suffered less damages than surrounding districts. This phenomenon is expressed by the word called as "shade of Mount Hiji" in Hiroshima. In this research, a basic experiment to verify the topographic effects of Mount Hiji on the shock wave of the atomic bomb was carried out. In this basic experiment, by using the shadowgraph method, behaviors of the shock wave passing a topographical model of isosceles triangle and Mount Hiji model. Pressure measurement behind the model was also conducted in the experiment. As a result of the experiment, basic information on the phenomenon in which the shock wave was shielded by Mount Hiji and did not reach much to Danbara district was obtained.

It is well known that the flow-field over blunt and pointed bodies is sensitive to the non-equilibrium phenomena characteristic of high enthalpy hypersonic flows. Till date, most experiments and modelling were related to flows essentially dominated by the dissociation rate. However, in practical cases of a re-entry low density flow, the aerodynamic quantities such as the shock shape and location may also be strongly influenced by vibrational relaxation coupled with dissociation and chemical reactions. Thus, the flow about various bodies such as spheres, hemisphere–cylinders and cones is recomputed using a chemical model recently proposed by the authors and by taking into account the coupling between the vibrational relaxation and the chemical kinetics. Then, the computed shock shapes in air flow are compared to recent experimental results obtained in a ballistic range for flight velocities between 2,500 and 4,000 m/s, and in a shock tunnel for enthalpies close to 5 and 10 MJ/kg. The computed density field around hemispherical bodies is also compared to the experimental one. A good agreement, within 5%, between computed and measured results is observed. A few comparisons are also proposed with the results obtained with another well-known (empirical) model. A comparison is also made between the flow quantities along the stagnation line obtained over cylindrical and spherical bodies using the present model and those coming from a quasi-one-dimensional model recently developed, showing also a satisfactory agreement.

This paper reports the result of a primary experimental and analytical study used to explore a reliable technology that is potentially applicable to the inactivation of micro-creatures contained in ship ballast water. A shock wave generated by the micro-explosion of a 10mg silver azide pellet in a 10mm wide parallel test section was used to interact with a bubble cloud consisting of bubbles with average diameter 10µm produced by a swirling flow type micro-bubble generator. Observations were carried out with a high-speed camera, IMACON200, and the corresponding rebound pressures of the collapsing bubbles were measured with a fiber optic probe pressure transducer that provides high spatial and temporal resolutions. We found that micro-bubbles collapse in several hundred nanoseconds after the shock exposure and the resulting peak pressure pulses that repeatedly occurred exceeded well over 200MPa measured at the 20mm distance from the explosion center. These continued for well over 20µs. The experimental pressure responses were explained by solving the one-dimensional bubble Rayleigh-Plesset equation. Such high peak pressures could be used effectively for the inactivation of micro-creatures contained in ship ballast water.

The focus of the current study is to examine experimentally the diffracted shock wave pattern and the consequent vortex loop formation, propagation, and decay from nozzles having singular corners. Non-intrusive qualitative and quantitative techniques: schlieren, shadowgraphy, and particle image velocimetry (PIV) are employed to analyze the induced flow-fields. Eye-shaped nozzles were used with the corner joints representing singularities. The length of the minor axes are a = 6 and 15 mm, with the major axis b = 30 mm for both cases. The experiments are performed for flow Reynolds numbers in the range 0.8 × 105 and 4.6 × 105. Air is used in both driver and driven sections of the shock tube.