锥形长药柱水下爆炸冲击波参数计算方法

为了计算锥形长药柱水下爆炸冲击波压力,以及研究长脉宽冲击波的传输特性,基于叠加原理建立了冲击波压力-时间曲线的计算方法,通过实验验证了该方法的有效性,在此基础上分析了锥形长药柱不同方位冲击波压力的分布规律。研究结果表明:锥形长药柱产生的冲击波压力具有各向异性,在起爆端一侧形成的是具有厚波头特征的低幅值长脉宽冲击波,在装药径向形成的是接近指数衰减的高幅值冲击波,而在远离起爆端的冲击波压力幅值和脉宽则介于前两者之间。锥形长药柱与球形装药冲击波分布的差异是由于装药形状和起爆方式的改变所导致的,由于装药不同部位起爆的时间差,导致水下爆炸冲击波在不同位置的叠加效果存在明显差异,药柱周围流场中形成的冲击波压力具有方向性。利用提出的计算方法得到的计算结果与实验结果和数值模拟结果吻合较好,研究结果可为锥形长药柱水下爆炸冲击波威力场和毁伤评估提供参考和依据。     

Shock Hugoniot and equations of states of water,castor oil,and aqueous solutions of sodium chloride,sucrose and gelatin

This paper reports a result of experiments for the determination of reliable shock Hugoniot curves of liquids, in particular, at relatively low pressure region, which are needed to perform precise numerical simulations of shock wave/tissue interaction prior to the development of shock wave related therapeutic devices. Underwater shock waves were generated by explosions of laser ignited 10 mg silver azide pellets, which were temporally and spatially well controlled. Measuring temporal variation of shock velocities and over-pressures in caster oil, aqueous solutions of sodium chloride, sucrose and gelatin with various concentrations, we succeeded to determine shock Hugoniot curves of these liquids and hence parameters describing Tait type equations of state.     

Unsteady waves in a viscous fluid of finite depth

Here we study the plane and three-dimensional problems of unsteady waves which arise on the surface of a viscous fluid of finite depth under the influence of a velocity pulse applied on the bottom of the basin.The problem is considered as the simplest scheme for studying, with account for the effect of viscosity, the propagation of waves of the tsunami type which result from an underwater shock.Similar problems on the propagation of waves which arise from initial surface disturbances are considered in [1–9].     

The effect of shock pressures on the inactivation of a marine Vibrio sp.

The effect of shock pressures on the inactivation of a marine Vibrio sp. was studied experimentally and numerically. In the experiment, an aluminum impactor plate accelerated by a gas gun was used to induce shock waves in a sealed aluminum container with cell suspension liquid inside. The shock pressures in the container were measured by a piezofilm gauge. Several 10–100 MPa of pressure were measured at the shock wave front. An FEM simulation, using the Johnson–Cook model for solid aluminum and the Tait equation for the suspension liquid, was carried out in order to know the generation mechanism of shock pressures in the aluminum container. The reflection, diffraction and interaction of shock waves at the solid–liquid boundaries in the aluminum container were reasonably predicted by the numerical simulation. The changes in shock pressures obtained from the computational simulation were in good agreement with those from the experiment. The number of viable cells decreased with the increase of peak pressures of the shock waves. Peak pressures higher than 200 MPa completely inactivated the cells. At this pressure, the cell structures were deformed like the shape of red blood cells, and some proteins leaked from the cells. These results indicate that the positive and negative pressure fluctuations generated by shock waves contribute to the inactivation of the marine Vibrio sp.      

Overpressure generation and repetition of collapsing microbubbles induced by shock wave reflection in a narrow gap

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.     

Characteristics of impact-driven high-speed liquid jets in water

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.     

Wave field of a directed explosion

We consider an underwater gas explosion in a cylindrical tank which is open at the bottom. The pressure field in the water is a toroidal compression wave with gradually increasing pressure behind the wave front. In the linear approximation the pressure shock occurs only under the cylinder with the gas. Filling of the lower portion of the cylinder with water alters the compression wave profile.The results obtained may be used in marine seismological prospecting for developing sources for exciting elastic vibrations which are not hazardous to the fish population, in explosive cleaning of filters in water wells, etc.     

Comparison of different methods of measurement of pressure of underwater shock waves generated by electrical discharge

Different methods for measurement of strong underwater shock waves pressure pulses with peak pressures of up to 200 MPa and rise time of tens to hundreds of nanoseconds are described and compared. The experimental techniques include direct methods of pressure measurement using various electromechanical gauges such as quartz, carbon-based, and commercially available PCB gauges, and nondirect methods based on measurement of the velocity of the shock wave such as time-of-flight and fast-streak photography. Advantages and disadvantages of the used gauges and methods are discussed. The shock waves were produced by underwater electrical discharge (discharge current amplitude ≤100 kA, pulse duration ≤5 μs) initiated by an exploding wire. A good correspondence between the pressure amplitudes measured by the various gauges and methods was observed. The obtained dependence of the shock wave pressure on the distance from the discharge channel was found to be best fitted by a r ^−0.7 law. It is also shown that none of these methods can be used to determine the time evolution of the pressure behind the front of the shock wave.     

底部近距离爆炸下舱段模型毁伤试验研究

底部近距离爆炸可对水面舰船造成致命性打击，为探究其破坏机理，本文中开展了底部近距离爆炸下舱段模型的毁伤试验，获取了舱段模型破损区域试验数据、非破损区域的冲击环境数据。同时借助舷侧近距离爆炸试验结果、底部中远场爆炸试验结果，综合对比可发现:（1）底部近距离爆炸下，舱段模型会呈现整体隆起变形、爆心区域撕裂并伴有较大凹陷变形、舷侧外板大面积屈曲失稳等典型特征；（2）相比舷侧爆炸方位，底部爆炸对舱段模型具有很强的综合毁伤效果，底部爆炸相对舷侧爆炸对舱段模型的综合毁伤效果可提高40%以上；（3）在冲击环境方面，底部近距离爆炸下非破损区域测点中高频段的冲击谱曲线变化趋势基本与中远场爆炸一致，但在低频阶段，底部近距离爆炸下的谱位移要远高于中远场爆炸工况。     

Application of underwater shock wave and laser-induced liquid jet to neurosurgery

Paper deals with applications of underwater shock waves to medicine. A historical development of underwater shock wave generation by using pulsed Ho:YAG laser beam irradiation in water is briefly described and an overview is given regarding potential applications of shock waves to neuro-surgery. The laser beam irradiation in a liquid-filled catheter produces water vapor bubble and shock waves intermittently produces micro-liquid jets in a controlled fashion from the exit of the catheter. Correlations between shock dynamics and bubble dynamics are emphasized. To optimize the jet motion, results of basic parametric studies are briefly presented. The liquid jet discharged from the catheter exit has an impulse high enough to clearly exhibit effectiveness for various medical purposes. In liquid jets we observed reasonably strong shock waves and hence invented a compact shock generator aiming to apply to microsurgery. We applied it to a rat's bone window and developed an effective method of brain protection against shock loading. The insertion of Gore-Tex® sheet is found to attenuate shock waves drastically even for very short stand off distance and its physical mechanism is clarified. The laser-induced liquid jet (LILJ) is successfully applied to soft tissue dissection. Animal experiments were performed and results of histological observations are presented in details. Results of animal experiments revealed that LILJ can sharply dissect soft tissue with a minimum amount of liquid consumption, while blood vessels larger than 0.2 mm in diameter are preserved. Shock waves and LILJ have a potential to be indispensable tools in neuro-surgery.This paper was based on work that was presented at the 2nd International Symposium on Interdisciplinary Shock Wave Research, Sendai, Japan, March 1–3, 2005.Communicated by K. Takayama PACS 42.62.Be, 47.40.-x, 42.62.-b     

Investigation of wave fields in a fluid layer and elastic half-space excited by a near-bottom source of vibrations

Questions of a study of acoustic and seismic wave propagation in the ocean and the underlying medium, associated with problems of marine hydrolocation (sonar) and the investigation of tsunami wave predecessors caused by underwater volcanic eruptions are of great interest at this time. The simplest model, a point source of vibrations located in a fluid layer at a certain range from the bottom, is used to describe the mentioned wave processes. Wave fields in a fluid and elastic base are investigated in this paper, analytical formulas are obtained, and results of a numerical analysis are presented.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 49–51, July–August, 1984.     

水下爆炸气泡脉动测量及分析

水下爆炸气泡破坏效应是水中兵器的重要毁伤模式之一。为研究水下爆炸气泡脉动现象,建立了小当量水下爆炸实验系统,并进行了爆炸当量分别为0.125g、1.0g、3.375g和8g TNT的水下爆炸实验。采用球形PETN装药并中心起爆,产生球形对称的气泡和冲击波载荷,并利用高速摄像系统记录水下爆炸气泡脉动过程,以及布置压力传感器测量水中冲击波压力。实验获得了清晰的水下爆炸气泡脉动过程图像,得到了冲击波和气泡脉动压力曲线。对数字化图像进行判读,得到气泡脉动直径和周期。另外根据冲击波曲线测量了气泡脉动周期,对比分析了气泡脉动相关参数。结果表明,高速摄像数据测量的气泡直径与经验公式较接近,高速摄像测量的气泡周期与冲击波曲线测量的气泡脉动周期以及经验公式结果具有较好的一致性。本文提出的实验技术安全、经济、可靠,气泡脉动参数判读精确,满足水下爆炸气泡脉动研究需求。     

气泡及其破碎兴波对浮动冲击平台影响探究

基于LS-DYNA软件中的ALE算法，对近水面水下爆炸气泡脉动过程进行数值模拟并与实验结果进行对比，验证了近水面近壁面混合边界有限元模型和参数设置的正确性。设置不同爆炸工况，对气泡及其破碎兴波对浮动冲击平台影响进行探究，结果表明:在水下爆炸过程中，气泡、自由面、浮动冲击平台会发生强烈的耦合作用，在气泡脉动阶段，气泡会诱导出涌流和水冢效应，影响浮动冲击平台的安全性和使用性；冲击波是影响浮动冲击平台冲击环境的主要因素，由于气泡的低频性，气泡脉动及水冢对浮动冲击平台的直接冲击作用，会小幅度增加浮动冲击平台冲击环境的谱速度值、谱位移值，对谱加速度值几乎无影响；水冢抨击水面所形成的波浪和气泡破碎兴波，对浮动冲击平台造成的激励载荷呈周期性，其周期与波浪周期相同。波浪的激励载荷仅通过激励其对应频率的浮动冲击平台共振来改变平台的冲击环境。波浪载荷很小，对浮动冲击平台的冲击环境影响较小。     

Cavitation phenomena in extracorporeal microexplosion lithotripsy

An experimental investigation was made of cavitation phenomena induced by underwater shock wave focusing applied to the extracorporeal microexplosion lithotripsy (microexplosion ESWL). Firstly an underwater microexplosion generated by detonation of a 10 mg silver azide pellet was studied and secondly underwater shock focusing and its induced cavitation phenomena were investgated. Underwater shock wave was focused by using a semi-ellipsoidal reflector in which a shock wave generated at the first focal point of the reflector was reflected and focused at the second focal point. It is found that an explosion product gas bubble did not produce any distinct rebound shocks. Meantime cavitation appeared after shock focusing at the second focal point where expansion waves originated at the exit of the reflector were simultaneously collected. A shock/bubble interaction is found to contribute not only to urinary tract stone disintegration but also tissue damage. The cavitation effect associated with the microexplosion ESWL was weaker in comparison with a spark discharge ESWL. The microexplosion ESWL is an effective method which can minimize the number of shock exposures hence decreasing tissue damage by conducting precise positioning of urinary tract stones.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

Repeated application of shock waves as a possible method for food preservation

In order to study the possibility of using underwater shock waves to cause death in non desired microorganisms found in certain foods, Escherichia coli in suspension was exposed to hundreds of shock waves on an experimental electrohydraulic shock wave generator. Using a parabolic reflector it was possible to produce a plane shock front and expose many test tubes to the action of the shock waves at the same time and under the same conditions. The amount of surviving bacteria was determined by plate counting for different numbers of applied shock waves. Pressure measurements using needle hydrophones are also reported. Experimental results indicate that electrohydraulically generated shock waves are capable of producing a significant reduction in an E. coli population. An increase in the applied shock wave number produced a nearly exponential reduction in the E. coli population. Received 8 April 1998 / Accepted 17 September 1998     

Experimental and numerical study of shock wave propagation in water generated by pulsed arc electrohydraulic discharges

The objective of this study is to simulate the propagation of the shock wave in water due to an explosion. The study is part of a global research program on the development of an alternative stimulation technique to conventional hydraulic fracturing in tight gas reservoirs aimed at inducing a distributed state of microcracking of rocks instead of localized fracture. We consider the possibility of increasing the permeability of rocks with dynamic blasts. The blast is a shock wave generated in water by pulsed arc electrohydraulic discharges. The amplitude of these shock waves is prescribed by the electrohydraulic discharges which generate high pressures of several kilobars within microseconds. A simplified method has been used to simulate the injected electrical energy as augmentation of enthalpy in water locally. The finite element code EUROPLEXUS is used to perform fluid fast dynamic computation. The predicted pressure is consistent with the experimental results. In addition, shock wave propagation characteristics predicted with simulation can be valuable reference for design of underwater structural elements and engineering of underwater explosion.     

Focused tandem shock waves in water and their potential application in cancer treatment

The generator of two focused successive (tandem) shock waves (FTSW) in water produced by underwater multichannel electrical discharges at two composite electrodes, with a time delay between the first and second shock waves of 10  $\upmu $ s, was developed. It produces, at the focus, a strong shock wave with a peak positive pressure of up to 80 MPa, followed by a tensile wave with a peak negative pressure of up to $-80$  MPa, thus generating at the focus a large amount of cavitation. Biological effects of FTSW were demonstrated in vitro on hemolysis of erythrocytes and cell viability of human acute lymphoblastic leukemia cells as well as on tumor growth delay ex vivo and in vivo experiments performed with B16 melanoma, T-lymphoma, and R5-28 sarcoma cell lines. It was demonstrated in vivo that FTSW can enhance antitumor effects of chemotherapeutic drugs, such as cisplatin, most likely due to increased permeability of the membrane of cancer cells induced by FTSW. Synergetic cytotoxicity of FTSW with sonosensitive porphyrin-based drug Photosan on tumor growth was observed, possibly due to the cavitation-induced sonodynamic effect of FTSW.     

水下连续脉冲冲击波的声学特性

为探求金属爆炸索在水下爆炸声源研究领域的应用前景,设计了一种可以连续产生若干个脉冲冲击波的装置,称之为水下连续脉冲冲击波发生装置。利用小波分析对该装置产生的连续脉冲冲击波信号进行分解与重构,考察其频谱特性,并进一步分析了信号的声压级特性。结果表明:该装置产生的信号声压级较高,具有很强的声功率;信号包含频率十分丰富,雷管和金属爆炸索由于装药结构及传爆方式的不同,爆炸所产生的冲击波频谱特性也有所差异。雷管爆炸产生的冲击波主要分布在15.6 kHz以下的频带内,金属爆炸索爆炸产生的脉冲冲击波信号则主要分布在62.5 kHz以下的频带内;脉冲冲击波的个数和声持续时间可由爆炸索的排列方式和长度控制,脉冲冲击波间的时间间隔可调,发生装置稳定易控     

影响大黄鱼的水中声指标

为了明确有效地评价声波对大黄鱼影响的指标,以水下爆破和滨海山体爆破两种作业方式产生的水中声波数据为基础,进行声波信号的声压峰值和声暴露级分析,并结合现场大黄鱼的行为响应进行研究。结果表明:水下爆破产生的水中声波瞬态声压幅值较高,能量在瞬间累积到最大值并影响大黄鱼的行为和安全;而滨海山体爆破水中声波的声压幅值小,声暴露时间长,能量的连续累积造成了大黄鱼行为的改变。由于两种爆破方式作用下的水中声波在不同的声暴露时间内的声暴露级较接近,且超过150 dB会造成大黄鱼的行为异常,因此认为声暴露级是评价水中声波对大黄鱼影响的一个重要指标。