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Showing papers on "Shock tube published in 1978"


Journal ArticleDOI
TL;DR: In this article, the results of experiments on plane shock waves refracting at air/SF6 and He/CO2 interfaces were presented, based on a generalization of the von Neumann (1943) classification of shocks into two classes called weak and strong.
Abstract: This paper presents the results of experiments on plane shock waves refracting at air/SF6 and He/CO2 interfaces. These are called fast-slow gas combinations because the speed of sound in the incident shock gas is greater than that in the transmitting shock gas. Our work was based on a generalization of the von Neumann (1943) classification of shocks into two classes called weak and strong. We introduced two subclasses of each of these, giving in all four groups of phenomena for study. This is possibly an exhaustive list, at least for conditions where the gases are approximately perfect. We present data on all four groups and study various transition conditions both within and across the groups. Our results appear to conflict with a previously reported irregular refraction; in fact we could apparently completely suppress this wave system by attention to our gas purity and boundary conditions. In its place we found a different system which appears to be a new phenomenon. We found another new system which has the appearance of a Mach-reflexion type of refraction but with its shock dispersed into a band of wavelets. It is interesting that the wavelets remain intense enough to induce identifiable vortex sheets in the flow. Finally we found yet another refraction of the Mach-reflexion type which had no detectable vortex sheet emanating from the triple point: such a system was foreshadowed by von Neumann.

90 citations


Journal ArticleDOI
TL;DR: In this article, the results of experiments with shock waves refracting at a CO2/CH4 interface were presented, which indicated that there exist at least four different free precursor refractions.
Abstract: This paper describes the results of our experiments with shock waves refracting at a CO2/CH4 interface. The refraction is slow-fast because the speed of sound in the incident gas (CO2) is less than that in the transmitting gas (CH4). We found three phenomena which apparently have not been reported before and which all have free precursor shocks in their wave systems; schlieren photographs of them are presented. As a result of the present and earlier work, we can assert that there exist at least four different free precursor refractions. Theoretical studies suggest that the slow-fast phenomena can be conveniently classified into three groups characterized by different ranges of values of the inverse strength ζi of the incident shock i. The classification may be an exhaustive list of the phenomena, at least when the gases are nearly perfect, but we cannot be sure. We present experimental data on all the phenomena in each group, including data on the transition conditions from one wave system to another both within and across the groups.

79 citations


Journal ArticleDOI
TL;DR: In this article, the authors deal with the mechanism of an impulsive pressure generated by a collapsing bubble in a water filled shock tube and apply an expansion wave and a subsequent compression wave to single, twin and triadic bubbles.
Abstract: This paper deals experimentally with the mechanism of an impulsive pressure generated by a collapsing bubble. In a water filled shock tube, an expansion wave and a subsequent compression wave are applied to single, twin and triadic bubbles. The growth, collapse and rebound of bubbles situated at various distances from a solid boundary are observed by means of high-speed photography and in-line Fraunhofer holography using a pulsed dye laser. The results indicate that the impulsive pressure is caused by a shock wave radiated at the instant of the rebound of a collapsing bubble, and that the subsequent jet impingement does not produce any detectable effects. The pressure pulse is found to be of the order 104 ∼ 105 atm, and its duration 2 ∼ 3 μsec.

60 citations


Journal ArticleDOI
TL;DR: In this paper, the paths of single particles were calculated for the initial state of erosion when the flow in the shock tube boundary layer was still laminar, based on the agreement between the measured height of the cloud and the calculated height of flight of the particles.

51 citations


Journal ArticleDOI
TL;DR: In this article, it is suggested that the flow of the liquid in foam cells has to be taken into account in order to predict the behavior of shock waves in foams, and the nature of the gas which fills the cells is shown to have a strong effect on the quenching of blast waves in foam.

38 citations


Journal ArticleDOI
TL;DR: In this paper, a systematic procedure was developed for listing all possible reactions which could occur between pairs of reagents included within a specified list of molecules and molecular fragments, and a set of criteria was formulated for eliminating from this very large set of possible reactions all those which were significantly less important than the dominant steps retained in the final mechanism.

36 citations


Journal ArticleDOI
TL;DR: In this article, the relative reliability of the comparative and absolute rate methods as they are applied to kinetic studies in the single-pulse shock tube was examined and it was concluded that reliable kinetic data can be obtained by the absolute rate (isolation technique) method with careful examination of the gas-dynamic flow conditions and taking cognizance of the incident shock deceleration.
Abstract: This investigation presents a detailed examination of the relative reliability of the comparative and absolute rate methods as they are applied to kinetic studies in the single-pulse shock tube. For this purpose two previously studied reactions, the thermal elimination of HCl from ethyl chloride and n-propyl chloride, were selected and mixtures of these compounds were shock heated to temperatures in the range of 960°-1100°K. The experimental results were analyzed by both methods and the rate constants obtained from these analyses are compared with those of previous studies. The advantages and shortcomings of both methods are noted and it is concluded that reliable kinetic data can be obtained by the absolute rate (isolation technique) method with careful examination of the gas-dynamic flow conditions and taking cognizance of the incident shock deceleration. The limitations of the comparative rate technique encountered in the present study were similar to those detailed in previous investigations.

35 citations


Journal ArticleDOI
TL;DR: In this paper, three methanol-air flames (9.3, 12.6, and 16.9% by volume) have been stabilized on a flat-flame burner and their concentration, and temperature profiles have been measured.

34 citations


Journal ArticleDOI
TL;DR: In this article, an implicit six-point finite-difference scheme for solving two-temperature, laminar, boundary-layer flows not in chemical equilibrium in ionizing argon is presented.
Abstract: Details are given of an implicit six-point finite-difference scheme for solving two-temperature, laminar, boundary-layer flows not in chemical equilibrium in ionizing argon. The analysis extends previous work by considering the radiation-energy loss and the chemical reactions due to atom-atom and electron-atom collisions in the ionizing boundary-layer and free-stream flow. Also included are variations in transport properties based on known elastic-scattering cross-sections, effects of chemical reactions, radiation-energy loss and the electric-sheath wall boundary conditions. The results are compared with dual-wavelength interferometric boundary-layer data obtained by using a Mach-Zehnder interferometer 23 cm in diameter with the UTIAS 10 × 18 cm Hypervelocity Shock Tube for shocks of initial Mach numbers M s ∼ 13 and 16 moving into argon at a pressure p 0 ∼ 5 torr and temperature T 0 ∼ 297 °K. Considering the difficulties involved in solving such complex plasma flows, satisfactory agreement was obtained between analytic and experimental total-density profiles and electron-number-density profiles for the case M s ∼ 16 and good agreement for M s ∼ 13.

32 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of variation of temperature and molar density of the hydrocarbon on the induction time have been investigated, with the outcome that new correlations of data are presented, together with further insights into the reaction mechanisms involved.

26 citations


Journal ArticleDOI
TL;DR: In this paper, a computer program is written to calculate decompression wave velocities and the required thermodynamic properties are calculated using the Soave-Redlich-Kwong (SRK) equation of state.
Abstract: The events following rupture of a pipeline containing gas at high pressure are very similar to those following rupture of the diaphragm in a simple shock tube. A description of the decompression wave resulting from such a rupture, and its rate of propagation in natural gases is the primary purpose of this paper. A computer program is written to calculate decompression wave velocities. The required thermodynamic properties are calculated using the Soave-Redlich-Kwong (SRK) equation of state and the results of computed wave velocities are presented and compared to values observed in the decompression zone of a shock tube.

Journal ArticleDOI
TL;DR: The self-similar solution of the gasdynamic equations of a strong cylindrical shock wave moving through an ideal gas, with γ = cp/cv, is considered in this paper.
Abstract: The self-similar solution of the gasdynamic equations of a strong cylindrical shock wave moving through an ideal gas, with γ = cp/cv, is considered. These equations are greatly simplified following the transformation of the reduced velocity \[ U_1(\xi)\rightarrow U_1 = {\textstyle\frac{1}{2}}(\gamma + 1)(U+\xi). \] The requirement of a single maximum pressure, dζP = 0, leads to an analytical determination of the self-similarity exponent α(γ). For gases with γ < 2 + 3½ the slight maximum pressure occurs behind the shock front, nearing it as γ increases. For γ < 2 + 3½, this maximum ensues right at the shock front and the pressure distribution then decreases monotonically. The postulate of analyticity by Gelfand and Butler is shown to concur with the requirement dζP = 0. The saturated density of the gas left in the wake of the shock is computed and − U is shown to be the reduced velocity of sound at P = Pm.


ReportDOI
01 Aug 1978
TL;DR: In this article, the authors investigated the diffraction of shock waves in perfect and imperfect nitrogen and argon by sharp compressive corners (2 deg or = Theta sub w or = 60 deg) and established the transition boundaries between these regions.
Abstract: : The diffraction of shock waves (2 or = M sub s or = 8) in perfect and imperfect nitrogen and argon by sharp compressive corners (2 deg or = Theta sub w or = 60 deg) were investigated analytically and experimentally. It is shown that seven shock-wave diffraction domains exist in nitrogen and six in argon in the ranges 1 or = M subs or = 10 and 0 deg or = Theta sub w or = 90 deg. The domains consist of the four well-known shock wave reflections, i.e., regular reflection (RR), single-Mach (SMR), complex-Mach (CMR) and double-Mach (DMR) reflections. All the transition boundaries between these regions were established analytically and substantiated by the present experimental results as well as the data from other sources. Over 100 experiments were conducted in the UTIAS 10 x 18 cm Hypervelocity Shock Tube equipped with a 23-cm dia field of view Mach-Zehnder interferometer equipped with a dual-frequency laser light source. It is shown that real-gas effects have a significant influence on the size of the regions and their transition boundaries. Some comparison between steady and nonstationary reflections are made and discussed. Isopycnics (lines of constant density) as well as density distributions along the wedge surface are presented for the various diffraction processes and their differences and similarities are discussed. (Author)

Journal ArticleDOI
TL;DR: In this paper, the central structure of the Stark-broadened Balmer line Hbeta has been analyzed in the plasma produced behind the reflected shock in a combustion-driven shock tube of internal diameter 10 cm. The incident shock is propagated at a Mach number typically of M=8 in a mixture of 0.5% H2(D2), 80% Ne, 20% He (Ar), creating in the reflected-shock region temperatures close to 104K and electron number densities 1016
Abstract: The central structure of the Stark-broadened Balmer line Hbeta has been analysed in the plasma produced behind the reflected shock in a combustion-driven shock tube of internal diameter 10 cm. The incident shock is propagated at a Mach number typically of M=8 in a mixture of 0.5% H2(D2), 80% Ne, 20% He (Ar) at an initial pressure of 10 Torr creating in the reflected-shock region temperatures close to 104K and electron number densities 1016

Journal ArticleDOI
TL;DR: In this article, the formation and propagation of shock waves in a two-component flowing bubbly mixture has been investigated experimentally and the structure of the shock wave formed by steepening of compression waves is compared with the corresponding features of shocks produced spontaneously in shock tubes.

Journal ArticleDOI
TL;DR: In this paper, a series of initially planar shock waves were allowed to expand from a shock tube into a near half-space, and the strength of the wall shock was measured at two positions on the slightly concave front wall.
Abstract: A series of initially planar shock waves was allowed to expand from a shock tube into a near half-space. The strength of the wall shock was measured at two positions on the slightly concave front wall. These measurements are compared with shock strengths predicted by a shock-dynamic model based on the cylindrical expansion of a critical shock. Chisnell's (1957) theory is used to account for the effect of the increasing surface area of the expanding wall shock, and Whitham's (1957) treatment to correct for the curvature of the wall. The critical shock strength is obtained from Skews’ (1967) experimental measurements of the Mach number of the self-similar wall shock following two-dimensional diffraction at a 90° edge.The model predicts the relatively small degree of attenuation observed between the measuring stations, but overestimates the absolute shock strength. The most likely cause is that, in the early stages of expansion, the wall shock experiences further attenuation owing to its interaction with the expanding flow. These effects are shown to be short range and of negligible importance at the first measuring station, 1·86 tube diameters from the axis. Thus, using the experimental results at this station as the starting point, the model predicts accurately the shock strength at 3·76 diameters. It is concluded that Chisnell's theory can be applied to the weakening of the wall shock in ducts with large abrupt changes in cross-section only when the wall shock is some distance from the entrance to the area change.

ReportDOI
01 Aug 1978
TL;DR: In this article, the authors describe experiments in which cold liquids (Freon-11, Freon-22, water, or butanol) were impacted upon various hot materials (mineral oil, silicone oil, water and mercury, molten Wood's metal or molten salt mixture).
Abstract: The contact of two liquid materials, one of which is at a temperature substantially above the boiling point of the other, can lead to fast energy conversion and a subsequent shock wave. This phenomenon is called a vapor explosion. One method of producing intimate, liquid-liquid contact (which is known to be a necessary condition for vapor explosion) is a shock tube configuration. Such experiments in which water was impacted upon molten aluminum showed that very high pressures, even larger than the thermodynamic critical pressure, could occur. The mechanism by which such sharp pressure pulses are generated is not yet clear. The report describes experiments in which cold liquids (Freon-11, Freon-22, water, or butanol) were impacted upon various hot materials (mineral oil, silicone oil, water, mercury, molten Wood's metal or molten salt mixture).

Journal ArticleDOI
TL;DR: In this article, a series of experiments were conducted using kerosene drops of 388 μm diameter dispersed in air through use of a large number of hypodermic needles, and preliminary results relating to the effect of the size of the cloud gap on detonation velocity, quenching, and initiator energy levels required for detonation were discussed.

Journal ArticleDOI
Chul Park1
TL;DR: In this article, the sum of the electronic transition moments for the (E 1 Sigma +) - (X 1 Sigma+) band system of SiO has been determined from absorption measurements conducted in the reflected-shock region of a shock tube.
Abstract: The sum of the squares of the electronic transition moments for the (E 1 Sigma +) - (X 1 Sigma +) band system of SiO has been determined from absorption measurements conducted in the reflected-shock region of a shock tube. The test gas produced by shock-heating a mixture of SiCl4, N2O, and Ar, and the spectra were recorded photographically in the 150-230-nm wavelength range. The values of the sum of the squares were determined by comparing the measured absorption spectra with those produced by a line-by-line synthetic spectrum calculation. The value so deduced at an r-centroid value of 3.0 bohr was 0.86 + or - 0.10 atomic unit.

Journal ArticleDOI
TL;DR: In this paper, the authors used kinetic spectrophotometry in the wavelength range 250 nm-1.5 µm to investigate the products of pyrolysis and found that polyacetylenes were formed.
Abstract: Shock heating of acetylene and ethylene, under the conditions 1500–2500 K, 1–2 bar and molar fraction 0.07–2 % hydrocarbon in argon, has produced spectrographic evidence concerning the products of pyrolysis. Kinetic spectrophotometry was used in the wavelength range 250 nm-1.5 µm.The variation of the absorption spectra with temperature, hydrocarbon pressure and time were investigated, and suggest that polyacetylenes were formed.Simple kinetic analysis has given rate constants for the formation of polyacetylenes and the polyacetylene concentration was found to reach an equilibrium value within the observation time in some cases.

Journal ArticleDOI
TL;DR: In this article, the gas-phase decomposition of 1-methylcyclohex-1-ene has been studied over the temperature range of 1000°-1180° K in a single-pulse shock tube using a comparative-rate technique.
Abstract: The kinetics of the gas-phase decomposition of 1-methylcyclohex-1-ene has been studied over the temperature range of 1000°–1180° K in a single-pulse shock tube using a comparative-rate technique. The retro Diels-Alder reaction to ethylene and isoprene accounts for the bulk of the products with a rate constant given by


ReportDOI
30 Nov 1978
TL;DR: In this paper, the interferograms of a detailed study on the reflection of non-stationary oblique shock-waves using a 23 cm dia field of view Mach-Zehnder interferometer and the UTIAS 10 cm by 18 cm Hypervelocity Shock Tube are presented.
Abstract: : The interferograms of a detailed study on the reflection of non-stationary oblique shock-waves using a 23 cm dia field of view Mach-Zehnder interferometer and the UTIAS 10 cm by 18 cm Hypervelocity Shock Tube are presented in this separate report.

Journal ArticleDOI
TL;DR: In this article, the development of transverse magnetohydrodynamic shock waves has been studied in an electromagnetic shock tube for both parallel and antiparallel bias shock waves Radial magnetic field profiles indicate an essentially flat shock front is formed in both cases.
Abstract: The development of transverse magnetohydrodynamic shock waves has been studied in an electromagnetic shock tube for both parallel and antiparallel bias shock waves Radial magnetic field profiles indicate an essentially flat shock front is formed in both cases The shock and piston behavior is modeled by a simple snowplow model with a resistive arc across the launching endplate of the shock tube Mass leakage through the piston is necessary to explain the observed high shock speeds The method of characteristics is used to compute magnetic field profiles in excellent agreement with those observed experimentally

Journal ArticleDOI
TL;DR: It is shown that the advantages of piezoresistive gauges, such as short rise time, small dimensions, and in-material stress measurement, may be utilized for low shock pressure recording even in explosive environments, an area previously dominated by piezoelectric gauges.
Abstract: A new sensitive technique which permits the detection of small pressures in shock waves down to 5 bars with good time resolution has been developed. It consists of a pulsed double‐compensated Wheatstone bridge in conjunction with piezoresistive carbon gauge transducers. It is shown that the advantages of piezoresistive gauges, such as short rise time, small dimensions, and in‐material stress measurement, may be utilized for low shock pressure recording even in explosive environments, an area previously dominated by piezoelectric gauges. Comparative data for the two types of sensors are presented for shock tube side‐on and head‐on collision experiments and underwater explosions. This new development opens the possibility of PRG applications in classical fields of low shock pressure recording such as gas dynamics and underwater explosions.

Journal ArticleDOI
TL;DR: In this paper, an experimental study of the spatio-temporal evolution of the transition in a shock-tube wall boundary-layer has been carried out with thin film heat transfer gauges placed all along the tube.

Journal ArticleDOI
TL;DR: In this paper, the ignition delay for coal particles of 19 μ and 41 μ was determined in a 7.62 cm shock tube and the gas temperature behind the reflected shock wave, T 5, was calculated from the measured incident shock-wave speed.
Abstract: The objective of this study is to obtain the ignition delay for Pittsburgh seam coal particles shock heated in air to various temperatures and I atmosphere pressure. The ignition delay for coal particles of 19 μ and 41 μ was determined in a 7.62 cm shock tube. The gas temperature behind the reflected shock wave, T 5, was calculated from the measured incident shock-wave speed. Plots or the ignition dealy vs. T 5indicate the existence of a minimum gas temperature for ignition. The effect of particle size on the ignition delay is small for the particle size range used.

01 Jan 1978
TL;DR: In this article, the strongest shock-generating capability for an arc-driver system with the least total energy consumption is discussed, and several programs using the shock tube for developmental research in energy and industrial applications are outlined.
Abstract: High shock-tube velocities simulating Jovian entry have been achieved with arc-driver operation using a method of tailoring electrical circuit impedance to arc-plasma impedance. The concept of impedance matching also prescribes a requirement for minimum electrical capacitance. The technique of developing the strongest shock-generating capability for an arc-driver system with the least total energy is discussed. Several programs using the shock tube for developmental research in energy and industrial applications are outlined.

01 Nov 1978
TL;DR: In this paper, a study of flow development over a simple circular arc airfoil at zero angle of attack was carried out in a shock tube at low and intermediate Reynolds numbers to assess the testing technique.
Abstract: Performance analysis of a gas-driven shock tube shows that transonic airfoil flows with chord Reynolds numbers of the order of 100 million can be produced, with limitations being imposed by the structural integrity of the facility or the model. A study of flow development over a simple circular arc airfoil at zero angle of attack was carried out in a shock tube at low and intermediate Reynolds numbers to assess the testing technique. Results obtained from schlieren photography and airfoil pressure measurements show that steady transonic flows similar to those produced for the same airfoil in a wind tunnel can be generated within the available testing time in a shock tube with properly contoured test section walls.