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Objective of this research is high spatial resolution acquisition of measurement image in telescopic visualization measurement. Telescopic visualization measurements cannot be performed under strong atmospheric disturbances because of the spatial resolution degraded. So that, an adaptive optics system combining a deformable mirror and a wavefront sensor is used to reduce the influence of atmospheric disturbance. The visualization measurement uses a background-oriented schlieren method that has attracted attention for use in open-air. In this paper, the phase plate was used to conduct the experiment indoors. The phase plate was designed and manufactured from the result of measuring the atmospheric disturbance. In addition, the phase plate was combined into the adaptive optics system and experiments were performed.

Background Regarding blast injuries, fatal damage leading to immediate death is considered due to shock-lung, respiratory arrest, or circulatory failure induced by a neurological reflex, such as the severe vagal nerve reflex. It has not yet been determined whether a bulletproof vest protects against or aggravates shock-lung or the neurological reflexes considered to be fatal in the super-acute phase after an explosion. Purpose The purpose of this study was to clarify whether a bulletproof vest would protect the body in a pig blast model using a blast tube built at National Defense Medical College, which is the first such blast tube in Japan. Methods Seventeen pigs were divided into two groups: the body armor group (n = 6) and the non-body armor group (n = 11). Pigs underwent tracheal intubation with IV and A lines were secured to measure vital signs were checked and collect blood samples. Then, under intravenous anesthesia, the pigs were tightly fixed in the left lateral position on a table and exposed from the back neck to the upper lumbar back to the blast wave and wind with or without body armor, with the driving pressure of the blast tube set to 3.0 MPa. We checked the vital signs, collected blood samples, and observed the pigs for 3 hours after injury. Results When the surviving and dead pigs were compared, blood gas analyses revealed significant differences in PaO2, PaCO2, and pH in the super-early phase. In addition, all pigs injured by the blast wave and wind had lung hemorrhage, and 14 of 17 pigs had intra-abdominal hemorrhage with splenic injury. All 6 animals in the body armor group and 6 of the 11 animals in the control group survived for 3 hours after injury. Respiratory arrest immediately after exposure to the blast wave and wind was considered to influence the outcome in our pig model. Conclusions Respiratory arrest within several minutes after injury influenced the mortality of pigs. Body armor may have the beneficial effect in protecting against respiratory arrest immediately after an explosion.

Shock wave visualization around a circular cylinder with aerospike has been conducted to reveal characteristic of shock pulsation around supersonic parachute. The frequency of shock pulsation has been changed by valuing the ratio of the depth to the diameter, L/D, of the circular model that was valued from zero to two. Pressure history at the bottom of the circular cylinder model was recorded to analyze frequency of the shock pulsation. The characteristic of shock pulsation has strongly been affected by L/D in flow with strong disturbance.

A clear understanding of the mechanism responsible for large amplitude shock pulsations ahead of a hemispherical cavity in supersonic flow is presented for the first time in this article. This has applications in supersonic parachute decelerators during the atmospheric descent stage of aerospace vehicles. A cell-centered finite volume code FaSTAR is used to solve the full Navier–Stokes equations on a hemispherical shell facing a Mach 4.0 supersonic free stream. The numerical method is validated against earlier experimental results. First, Flow Configuration A appears consisting of an axisymmetric shock that undergoes low-amplitude oscillations. This flow transitions to Flow Configuration B that has an asymmetric shock structure and undergoes large-amplitude non-stationary shock pulsations. The shock stand-off distance in Flow Configuration B is 1.65 times that in Flow Configuration A. The generation of vortices from the curved shock, amplification of vortices of one kind due to the dynamics of the cavity flow, and further interaction of these amplified vortices with the shock in a loop causes the large-amplitude shock pulsations. The oscillation frequencies as determined from cavity pressure and shock stand-off distance signals extracted from the unsteady results are 1.26 kHz during Flow Configuration A, and 859 and 863 Hz during the non-stationary pulsations of Flow Configuration B. The Helmholtz resonator model predicts quite accurately the frequency of Flow Configuration A (1.27 kHz), and to a good extent the frequency in Flow Configuration B (916.7 Hz)., Conference: 21st International Shock Interaction Symposium (ISIS), Location: Riga, LATVIA, Date: AUG 03-08, 2014

Flow visualization using the background-oriented schlieren (BOS) technique was used to investigate the characteristics of the stagnation point shift near the nozzle base of a 20%-truncated planar plug nozzle designed for a Mach number of 2.87 at the nozzle exit. The nozzle pressure ratios ranged from 7 to 120. A shock tube with a cross-section of 3 × 4 cm is used as a high-pressure gas reservoir. The obtained images were compared with the Navier–Stokes numerical solution obtained with the weighted averaged flux method. First, to confirm the establishment of steady flow, the starting process inside the nozzle was visualized using shadowgraph. Next, BOS images were used to determine the location of the stagnation point inside the closed wake. The images revealed that the distance of the stagnation point from the base surface was 1.3 times the throat width after the closed wake mode was established.

This study describes an attempt of quantitative visualization of open-air explosions via the background-oriented schlieren method (BOS). The shock wave propagation curve and overpressure distribution were extracted from the obtained images and compared with the results of the numerical analysis. The potential of extracting the density distribution behind the shock front is also demonstrated. Two open-air explosions were conducted; one with a $$36$$ -kg emulsion explosive and the other with a $$7.89$$ -kg composition C4 explosive. A high-speed digital video camera was used with a frame rate of $$10{,}000\,\mathrm{Hz}$$ and a pixel size of $$800 \times 600$$ . A natural background, including trees and grass, was used for BOS measurements instead of the random dots used in a laboratory. The overpressure distribution given by the passing shock was estimated from the visualized images. The estimated overpressures agreed with the values recorded by pressure transducers in the test field. The background displacement caused by light diffraction inside the spherical shock waves was in good agreement, except at the shock front. The results shown here suggest that the BOS method for open-air experiments could provide increasingly better quantitative and conventional visualization results with increasing spatial resolution of high-speed cameras.

Experimental and numerical investigation has been made to reveal the characteristic of shock wave pulsation in front of a hemi-spherical model at supersonic speeds more above Mach 2. Three types of measurements by; high-speed schlieren, pressure transducers, and pressure-sensitive paint, were employed to make the relation between shock pulsation and pressure distribution on the inner surface of the model clear. Three-dimensional numerical analysis has also been carried out on the flow field around the model by using compressible fluid analysis code FaSTAR, which was developed by JAXA. Comparison between the experimental results and the numerical one summarized that the shock wave pulsation with about 800 Hz was initiated by the small disturbances generated by the bow shock in front of the model and developed inside it. The development of the small disturbances depends on the geometric configuration of the rip of the model. A new geometrical configuration of supersonic parachute for planetary probes would be proposed to suppress shock pulsation at decent phase into the planet atmosphere.

In this article, we attempt to validate flow visualization using the high-speed background-oriented schlieren (HiBOS) method, which is the BOS technique combined with a high-speed video camera as the recording device in the experiment. The method has been applied to shock-induced flow near the open end of a shock tube. Three incident shock Mach numbers were examined so that the BOS measurements could be compared with results given in the literature of particle-image velocimetry (PIV) measurements. Using the HiBOS technique, we were able to clearly view developing, compressible vortex rings and diffracted shock waves discharged from the open end of the shock tube. From the BOS images, we extracted the history of the propagation velocity, the diameter of the vortex ring, and the diameter of the vortex core, all of which agree with the corresponding PIV values reported in the literature.

Digital phase-shift holographic interferometry was applied to visualize weak shock waves and related phenomena quantitatively. This method of interferometry is an improved version of double-exposure holographic interferometry using digital image processing and a phase shift method. The obtained interferograms were analyzed using the Carre method. To evaluate the applicability of the interferometry to quantitatively visualize the phenomena, density profiles behind weak spherical shock waves generated with 500 μg of silver azide were examined. The results of the numerical analysis performed with the hydrocode AUTODYN were compared with those of the experiment. The Mach number of visualized shock waves was estimated to be 1.007 ± 0.001 at the pressure transducer near the test section. At the shock fronts, the density difference between the experimental and numerical results was within 0.3%.

The laser-induced thermal acoustics (LITA) method was used to measure the temperature profiles induced behind spherical shock waves, generated by high-voltage discharge in air with an energy of 6 J. A Nd:YAG laser (wavelength 532 nm, energy 300 mJ, pulse duration 10 ns, line width 0.005 cm−1) and an Ar-ion laser (wavelength 488 nm, power 4 W) served as the pump and probe lasers, respectively for the LITA measurements. The peak temperatures were in good agreement with results calculated with the Euler equations. The temperature profiles behind the shock, however, differed in decay rates. The peak temperatures behind the shock wave were determined by reflected overpressure and agreed with those from the LITA measurements within a maximum error of 5%.

Using a ballistic range with a small single-stage powder gun, characteristics of detached shock waves around cylindrical projectiles were investigated. The detaches shock waves were analyzed quantitatively by visualization method. The projectiles were made of steel, with a diameter of 5.56 mm and with a mass of 1.77 g. The projectiles were ejected into the test section of the ballistic range at supersonic speeds. Direction-indicating color schlieren method (DInCS) was used to visualize the flow field. The stand-off distance of the detached shock waves and the shape were obtained as the function of Mach number. The functions were compared with the results obtained by wind tunnel experiments. Analyzed images provided the quantitative information on shock shapes. The results were as follows: (1) the stand-off distances of the detached shock waves have been shown as exponential functions of Mach number; (2) the shapes of the shock waves have been found as quadratic functions of Mach number. The differences in the functions between this paper and a wind tunnel test were shown.

The flow visualization and force measurement of a supersonic impinging jet on a center-holed vertical baffle plate were investigated. Center-holed baffle plates of 2d to 5d in diameter, with a 1d center hole were tested, where d is the bore of the launch tube. The standoff distance of the baffle plates from the open end of the launch tube were varied to be from 2d to 5d. The supersonic impulse jet, with an incident shock wave of Mach 2.89 was produced by a high-enthalpy blast-wave simulator. The direction-indicating color schlieren method produced a two-dimensional density gradient of the flow field around the baffle plate. In addition, the flow fields were numerically analyzed, using two-dimensional asymmetric Euler equations. The results of the numerically-analyzed and the experimentally-visualized flow field agreed well. The visualized flow field indicates that the baffle plate should be at least 3.5d in diameter to deflect the supersonic impinging jet at an angle greater than a right angle. We have concluded that the representative method of designing muzzle brakes for military purpose accurately predicts the force yielded by the supersonic impinging impulse jet on the vertical baffle plate only when there is a large ratio of the baffle-plate diameter to the bore of the launch tube.

In order to investigate the developing characteristics of a high temperature supersonic impulse jet under an atmospheric ambient condition, we generate jets induced by an incident shock wave at Mach number 2.89, emerging from the open end of a high enthalpy blast wave simulator (HEBS). Developing high temperature supersonic impulse jets were visualized by the direction-indicating color schlieren method and analyzed by numerical calculations. A comparison of the experimental results with literature shows that the unsteady boundary area generated by the HEBS, starts to grow in half the time that the unsteady boundary area needs after the incident shock wave emerges in the literature.

Visualization of the flow field around a generic re-entry capsule in subsonic flow and shock wave visualization with cylindrical explosives have been conducted to demonstrate sensitivity and applicability of background-oriented schlieren (BOS) for field experiments. The wind tunnel experiment suggests that BOS with a fine-pixel imaging device has a density change detection sensitivity on the order of 10(sup -5) in subsonic flow. In a laboratory setup, the structure of the shock waves generated by explosives have been successfully reconstructed by a computed tomography method combined with BOS.

Aerodynamic deceleration devices including parachute have been widely used not for recovery system in atmospheric of the Earth but for entry system in that of other planet of solar system

This paper presents the results of an optical experiment which is carried out to measure the pressure and to observe the wave propagations when an explosion occurs in a model of a nuclear facility for preventing and mitigating the serious damage of nuclear facility. Numerical simulation is also performed to compare the phenomena in a model of nuclear facility. Nuclear facility is simulated as the several closed rooms in these experiments and simulations, because the nuclear facility is composed of many closed rooms. As a result, typical tendencies of pressure history are obtained, and it is confirmed that the explosion which occurs in a closed space is reflected in the complexity at the walls and interfered mutually with progressing waves. Finally, experimental results are compared with a numerical simulation. It is confirmed that the results of a numerical simulation show a good agreement with experimental results.

This paper presents the results of a visualization experiment which is carried out to measure the pressure and to observe the wave propagation when an explosion occurs in a model of a nuclear fuel cycle facility (NFCF). Numerical simulation is also performed to compare the phenomena in NFCF. NFCF is simulated as the several closed rooms in these experiments and simulations, because the NFCF is composed of many closed rooms. As a result, typical tendencies of pressure history and the behavior of the wave propagation are obtained, and it is confirmed that a wave caused by an explosion which occurs in a closed space propagates and reflects complexly, mutual interference with progressing waves is also observed. Finally, experimental results are compared with a numerical simulation. It is confirmed that the results of a numerical simulation show a good agreement with experimental results.

Joint development of a laser monitor for the real-time bio-tissue analysis is presented. The monitor is based on the digital dynamic laser speckle photography and deals with soft and hard bio-tissues. In soft tissues, the dynamic bio-speckles are formed in a scattered from a tissue laser light. An optically transparent model of hard bio-tissue was prepared and preliminary analysis of a stress field in the stressed model was performed using the dependence of the refractive index of transparent solids upon the state of stress and the double exposure speckle photography data. The refractive index of the stressed material was evaluated and the state of stress was reconstructed using the stress-optical law.

Schlieren photographs and shadowgrams have been evaluated to provide the radius-time histories of the shocks generated by explosions of silver azide charges with masses in the milligram range. Series of photographs of the flow field produced by a single explosion were obtained with an image converter camera, to yield a time history of the shock trajectory. These data were used to determine the shock Mach number and subsequently the peak hydrostatic overpressure as a function of radius. The pressure-radius profile was compared with that from a unit charge of TNT to determine the TNT equivalence of silver azide as a function of peak pressure and of distance from the centre of a $1\: \textrm{mg}$ silver azide charge. The shock radius and time were also determined from single-shot visualizations of silver azide explosions. A new method of analysis was developed so that the charge mass and the TNT equivalence of an explosion could be derived from such a single radius-time measurement. The TNT equivalence factor for silver azide was shown to vary from 0.3 to 1.4, depending on the distance from the centre of the explosion. This agrees well with the generally reported equivalence factor of about 0.4 (Baker et al. 1983), which was probably based on the chemical composition of the material. Procedures are described by which the TNT equivalence factor can be calculated at any specified distance from a silver azide charge of known mass, or from a measurement of the shock radius and time, even when the charge mass is not known. This factor can then be used to determine the physical properties of the TNT blast wave which best describe those from the silver azide charge at the specified distance. A further result of these studies was that the scaling laws for blast waves, whose validity has been verified for charge masses ranging from a few grams to hundreds of tons, i.e., for charge masses varying over more than nine orders of magnitude, also apply for charges with masses of the order of one milligram.

Parachutes are often used for planetary-entry and re-entry. Most of cases, parachutes are deployed at supersonic speed. Therefore, it is necessary to obtain aerodynamic characteristics at supersonic speed. However parachutes have wrinkles and seams. They make it difficult to study aerodynamic characteristics of the parachute shape. Therefore, experimental studies using solid models have been conducted from the 1960s re-entry program of the US [1]. In particular, Helmut G. Heinrich et al. visualized shockwaves, and shockwave vibrations in Mach number 3 [2]. These shockwave vibrations make the flow unstable, and the unstable flow gives model vibrations. They are risks of break.Therefore,Helmut G. Heinrich suggested an improved model.

This paper describes application of a background oriented schlieren (BOS) technique in order to obtain quantitative measurements of shock waves from explosions by processing high speed digital video recordings. To illustrate the technique we present results from analysis of two explosions, one by C-4, the other by emulsion explosives (EMX). The experimentswere performed at theMinistry of Defense Test field, and carried out by the Ministry of Economy, Trade and Industry (METI). The objective of this paper is to show that the shock wave overpressures in a field explosion test can be predicted quantitatively by means of this technique.

By applying two-reference beam interferometry together with digital data processing, a correspondingly modified double exposure holographic interferometer has been used to measure the density distribution in flow fields generated by very weak shock waves. The weak shock waves were generated by the explosion of milligram charges of silver azide, which were ignited by a pulsed Nd:YAG laser. With the help of this technique, density variations in a flow field associated with a shock Mach number Ms = 1.0007 were visualized and quantified. Phenomena that generated a sound intensity of 135dB could be resolved.

Using digital phase shift holographic interferometry (DPSHI), the internal density distribution of water which is sealed in a cylindrical cell has been measured under the condition that one of the cylinder end walls is oscillated by a PZT-actuator, which is driven by high frequency: 20kHz. The density distributions concerned with three different end wall pressures have been visualized and analyzed by DPSHI. Carre algorithm is employed for phase interpolation to reproduce phase maps. The absolute density changes in the cell have been demonstrated. The results have indicated that DPSHI can allow us to measure small density changes in narrow space under high frequency oscillation.

In this study, the method of digital phase shift holographic interferometry is applied to accurately measure the density distribution behind a weak shock wave. The goal of this investigation is to visualize and quantitatively evaluate flow fields behind weak disturbances, which are only marginally stronger than sound waves. In the present experiment, the shock Mach number was approximately Ms approximately equals 1.01. The wave was generated by the explosion of a small silver-azide (micro- charge) pellet, which was ignited by an Nd:YAG laser. Using phase shift interferometry, the phase distribution of the region far behind the incident shock could be detected.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Using laser-induced thermal acoustics, we demonstrate nonintrusive and remote sound-speed and temperature measurements in liquid water. Unsteady thermal gradients in the water sample produce fast, random laser beam misalignments, which are the primary source of uncertainty in these measurements. For water temperatures over the range 10 degrees C to 45 degrees C, the precision of a single 300-ns-duration measurement varies from +/-1 to +/-16.5 m/s for sound speed and from +/-0.3 degrees C to +/-9.5 degrees C for temperature. Averaging over 10 s (100 laser pulses) yields accuracies of +/-0.64 m/s and +/-0.45 degrees C for sound speed and temperature, respectively.