摘要:

Implosion of polygonally interacting shock system and consecutive explosion in a box with the square cross section were investigated numerically by using a TVD finite difference scheme of shock capturing family. Results obtained from initially regular‐polygonal form from the equilateral triangle to the octagon are shown in this paper.

ISSN:0094-243X    

DOI:10.1063/1.39435

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

On an ultrasonic imaging system a hyperechoic region was observed in a focal area of fucused shock waves in the dog kidney. This study was performed to learn whether cavitation bubbles are responsible for this hyperechoic region.The ultrasonic images in water of varying temperatures were not markedly different. In the flowing stream of distilled water, the stream was demonstrated as a hyperechoic region only with a mixture of air bubbles. Streams of 5%–50% glucose solutions were also demonstrated as a hyperechoic region. However, such concentration changes in living tissue, as well as thermal changes, are hardly thought to be induced.The holographic interferometry showed that the cavitation bubbles remained for more than 500 msec. in the focal area in water. This finding indicate that the bubble can remain for longer period than previously supposed.These results support the contentions that cavitation bubbles are responsible for the hyperechoic region in the kidneyin situ.

ISSN:0094-243X    

DOI:10.1063/1.39436

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A comparative study was made of damage to simulated kidney stones from spherical sector and focused hydrodynamic shock waves. Plaster cylinders of 40 bar static compressive strength were subjected to spherical shock waves with a time constant of 7 &mgr;sec generated by a conical shock tube. Near total destruction of the 2.5 cm by 2.5 cm cylinders to fine particles occurred with a single shock at a peak pressure of 0.85 kbar; onset of visible erosion at 0.5 kbar. Similar experiments performed in the diffraction region at a distance of 10 cm beyond the end of th shock tube with three repeated shocks of 0.34 kbar resulted in significant erosion. Similar targets located at the second focus of a semi‐ellipsoid reflector were subjected to multiple shock waves generated by an underwater electric arc located at the first focus. Progressive target erosion to fine particles occurred at the second focus as several hundred shocks were provided at the high pressure singularity. These experiments offer empirical insight important to modelling the response of calculi imbedded in biological tissue; e.g., kidneystones and gallstones, to shock waves of varied characteristics. Sector shock waves appear to offer potential for much more efficient and less traumatic medical application than focused shocks.

ISSN:0094-243X    

DOI:10.1063/1.39437

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Biological evidence of renal arterial wall damage induced by the microjet due to shock wave‐cavitation bubble interaction was demonstrated in living dog kidneys. We also intended to clarify the mechanism of renal tissue damage and the effects of different conditions of shock wave exposure (peak pressure of focused area, number of shots, exposure rate) on the renal tissue damage in comparison to stone disintegration.Disruption of arterial wall was the most remarkable histological change in the focused area of the kidneys. This lesion appeared as if the wall had been punctured by a needle. Large hematoma formation in the renal parenchym, and interstitial hemorrhage seemed to be the results of the arterial lesion. This arterial disorder also led to ischemic necrosis of the tubules surrounding the hematoma. Micro‐angiographic examination of extracted kidneys also proved such arterial puncture lesions and ischemic lesions.The number of shots required for model stone disintegration was not inversely proportional to peak pressure. It decreased markedly when peak pressure was above 700 bar. Similarly thenumber of shots for hematoma formation was not inversely proportional to peak pressure, however, this decreased markedly above 500 bar. These results suggested that a hematoma could be formed under a lower peak pressure than that required for stone disintegration.

ISSN:0094-243X    

DOI:10.1063/1.39438

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The von Neumann three‐shock theory does not adequately describe the conditions close to the triple point of the Mach reflection of weak shocks (M<1.5), and produces no solution for incident shocks with a Mach number less than about 1.25 in air. Experimental evidence, on the other hand, indicates that reflection does occur under these conditions, and it is suggested that the discrepancy is because the von Neumann theory assumes that the reflected and Mach stem shocks are plane oblique shocks bounding regions with uniform properties. In practice, the reflected shock and Mach stem are curved oblique shocks which bound regions with transverse gradients in their physical properties. The physical behind these shocks can be measured using infinite fringe interferometry. Alternatively, it will be shown that the physical properties behind these curved shocks can be determined from a shadow or schlieren photograph which gives information only about the position and shape of the shocks. The experimental observations suggest that the Mach stem and reflected shock in the region close to the triple point are approximately circular in cross section. Assuming circularity of the reflected and Mach stem shocks permits a determination of the angles between the shocks at the triple point and these, together with the observed triple point trajectory angle, can be used in a modified oblique shock solution which agrees with the experimental observations, if the condition for parallel flow on the two sides of the contact surface is relaxed. The shock polar representation of this solution is illustrated. It is concluded that Mach reflection of shocks with Mach numbers in the range 1.1<M<1.25 is possible, but the simple three shock theory is invalid.

ISSN:0094-243X    

DOI:10.1063/1.39439

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This paper deals with the shock reflection process at plane walls (wedges) which is known as pseudo‐steady. Questions still arise concerning the transition from regular reflection to irregular reflection, when the experimental transition data are compared to von Neumanns theoretical predictions. Recently several authors have shown experimentally that for weak incident shocks the transition takes place at wedges with inclinations at which the corner signal is able to catch up to the reflection point (sonic criterion). The paper intends to confirm this result for stronger incident shocks by the evaluation of visualized experiments. Furthermore it will be shown, by using gage measurements, that the corner signal is followed by a rather intensive rarefaction wave. This wave strongly influences the afterflow region of the reflected shock. The boundary conditions of the von Neumann Theory are discussed in light of this, and an approach by Skews is quoted.

ISSN:0094-243X    

DOI:10.1063/1.39440

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This paper shows the results of the continuing series of 1000‐lb HOB experiments conducted at both the Defense Research Establishment, Suffield, Canada and at the White Sands Missile Range, New Mexico, USA. A continuing objective of this series was to observe shock structure and flow characteristics in the transition region from regular to Mach reflection. Shot conditions, testbed layouts, and gage records are presented for tests at three different heights of burst.

ISSN:0094-243X    

DOI:10.1063/1.39441

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Recent and new Flash Photolysis‐Shock Tube results are reviewed and are compared to lower temperature results on the same reactions using a recently described procedure for boundary layer corrections in the reflected shock regime. A comparison is also made to the lower temperature results when the data bases are alternatively analyzed by ideal shock wave theory.

ISSN:0094-243X    

DOI:10.1063/1.39442

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Shock wave interactions with shallow transverse cavities are studied by means of toepler and interferometric methods in the range of shock Mach numbers 1.2–7.0. In order to study the development of various gasdynamical structures inside a cavity pressure history is measured in the middle of the cavity bottom. The pressure gauge data are compared with the results of two‐dimensional Whitham’s theory.

ISSN:0094-243X    

DOI:10.1063/1.39443

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Experimental and numerical studies on oblique reflection are shown for weak shock waves in carbon dioxide. The reflection patterns are observed in density contour fringes by using a Mach‐Zehnder Interferometer, and classified into four types by combinations of fully and partly dispersed waves in incident, merged (or Mach) and reflected shocks. The regions and transitions lines of reflection types are shown in a Ms‐&thgr; (Mach number‐ramp angle) plane. The reflection systems are additionally classified into two types of quasi‐regular reflection and quasi‐Mach reflection for partly dispersed waves. The detachment criterion of two‐shock theory can give a good prediction for transition from quasi‐regular reflection to quasi‐Mach reflection. Numerical simulation is carried out for a fully dispersed wave by using the MacCormack‐FCT combined method, and found to be in a good agreement with the experimental observation. Furthermore, the numerical results indicate the types of quasi‐regular and quasi‐Mach reflection also for fully dispersed waves.

ISSN:0094-243X    

DOI:10.1063/1.39444

出版商:AIP    

年代:1990

数据来源: AIP