Showing papers on "Shock tube published in 1974"
TL;DR: In this paper, the authors observed a gradual change in the structure of a gas-dynamic shock wave passing through a long tube of bubbly liquid, which they attributed to the motion of the bubbles relative to the liquid.
Abstract: We observed a gradual change in the structure of a shock wave passing through a long tube of bubbly liquid, which we attribute to the motion of the bubbles relative to the liquid. We show that the effect of the motion on the structure of a shock wave is like that of thermal relaxation on gasdynamic shock waves: the pertinent relaxation time is the time viscous forces in the fluid take to alter the velocity of a bubble to that of the fluid. Our theory predicts certain changes in the speed of the shock wave and in its structure. We could not verify the prediction as to wave speed: in dilute mixtures it is too small to be measured. But we report experiments on the structure of the wave, which support our theoretical conclusion that the observed changes are due to the relative motion.
160 citations
TL;DR: A normalized curve is presented which permits prediction of the functional dependence of the diaphragm opening aperture with time for different experimental conditions.
Abstract: An experimental study of the diaphragm opening process for various types of diaphragms and shock tube configurations is presented. A qualitative description of the opening process is given. A normalized curve is presented which permits prediction of the functional dependence of the diaphragm opening aperture with time for different experimental conditions.
61 citations
TL;DR: In this article, the ignition of ethylene-oxygen mixtures highly diluted with argon was studied in a shock tube by monitoring the emission from CH* and C2* or OH*, and the measurements covered the temperature range of 1400-2100 K at the C2H4/O2 ratios of 0.33-1.00.
Abstract: The ignition of ethylene-oxygen mixtures highly diluted with argon was studied in a shock tube by monitoring the emission from CH* and C2* or OH*. The measurements covered the temperature range of 1400–2100 K at the C2H4/O2 ratios of 0.33–1.00. From the observation of the CH*, C2*, and OH* emissions, a mechanism for the production of chemiluminescent species upon ethylene oxidation was briefly discussed, and from the observation of the induction period of the CH* emission, the following equation was found:logτ_CH[O_2]=-11.45+27.5×10^3/4.58T in units of s mol l−1, the rate-determining step being C2H3+O2→C2H3O+O.
56 citations
01 Jan 1974
TL;DR: The use of strong shocks in controlled thermonuclear devices was thought about long agol. as discussed by the authors showed that a so-called "thermonuclear shock" should have a tremendously high velocity of propagation.
Abstract: The use of strong shocks in controlled thermonuclear devices was thought about long agol. However, it turns out that a so-called “thermonuclear shock” should have a tremendously high velocity of propagation2. Many means are known which drive strong shocks through matter: high explosives, magnetic fields, electron beams, laser beams. The shock may or may not be followed by some kind of rarefaction.
39 citations
TL;DR: In this paper, a simplified theory of blast initiation of detonations in clouds of fuel in gaseous or droplet form is developed and agrees with the experiments described below, where the flow is at first dominated by the strong blast wave but transition from blast to detonation behavior occurs near a critical radius.
39 citations
TL;DR: The partial equilibrium state following the branched-chain explosion of shock-heated rich H2/O2/diluent mixtures contains a high concentration of H atoms.
Abstract: The partial equilibrium state following the branched-chain explosion of shock-heated rich H2/O2/diluent mixtures contains a high concentration of H atoms. The conditions under which this state can ...
39 citations
TL;DR: In this paper, a new flow model was presented on the interaction of the reflected shock with the boundary layer, based on the present and previous experimental data, and modifying the previous flow models.
Abstract: The region behind the reflected shock in a shock tube is used as a reservoir of gas for a hypersonic tunnel and in chemical kinetics studies. In order to clarify the gas properties in this region, the interaction phenomenon of the reflected shock with the boundary layer must be made clear. Although many studies have been carried out about this interaction, they are not comprehensive. In this paper, this interaction was observed optically by schlieren method, and the growth rate of the bifurcation and the velocity of the reflected shock were clarified. Furhter, based on the present and previous experimental data, and modifying the previous flow models, a new flow model was presented on the interaction of the reflected shock with the boundary layer. The growth rate of the bifurcation and the velocity of the reflected shock calculated by this model are in fair by good agreement with experimental results.
37 citations
TL;DR: In this article, the ignition of laser-supported detonation waves is caused by the thermomechanical response of the target, and the blown-off material acts as an accelerating piston creating a shock wave in air.
Abstract: The ignition of laser‐supported detonation waves is caused by the thermomechanical response of the target The blown‐off material acts as an accelerating piston creating a shock wave in air The small amount of free electrons created by the shock wave is cascaded to plasma densities by light absorption The theory explains a number of conclusions which have been experimentally verified Numerical results agree with observed data
37 citations
TL;DR: In this article, the authors used time-resolved pressure measurements on the end wall of a shock tube and, in some cases, as emission histories of the C2 Swan system (0-0 band) behind incident shock waves.
Abstract: Carbon monoxide dissociation-rate data were obtained over the temperature range 5600-12,000 K. The experiments were conducted with undiluted CO to emphasize rate constants applicable to molecular gas systems. Data were obtained as time-resolved pressure measurements on the end wall of a shock tube and, in some cases, as emission histories of the C2 Swan system (0-0 band) behind incident shock waves. Results confirm the presence of C2 as an intermediate species in CO decomposition.
34 citations
TL;DR: In this article, a shock tube technique was used to assess the impact fracture of bovine femur compact bone, in the form of cylindrical tube specimens, and the effect of wall thickness on the fracture pressure was established.
Abstract: A shock tube technique was utilized to assess the impact fracture of bovine femur compact bone, in the form of cylindrical tube specimens. The effect of wall thickness on the fracture pressure was established and an unique hoop stress (= 18.0 MN m−2) for fracture obtained. In addition, the effect of crack length and radius of curvature of the crack tip on the fracture hoop stress was established, together with a determination of Young's modulus at the shock loading rate. The possible correlations of these results with fracture mechanics concepts are discussed.
TL;DR: Shadowgraph techniques, using a Q-switched ruby laser as a light source, have been used to examine the shock waves produced in air and in water by focusing CO(2) TEA laser radiation at an air-water interface, finding that the shock speed in water decays to the sound speed within 0.5 microsec.
Abstract: Shadowgraph techniques, using a Q-switched ruby laser as a light source, have been used to examine the shock waves produced in air and in water by focusing CO2 TEA laser radiation at an air–water interface. It is found that the shock speed in water decays to the sound speed within 0.5 μsec, while the shock speed in air persists at values higher than the sound speed for times long compared to 0.5 μsec.
TL;DR: In this article, the vibrational relaxation times of DF(v = 1) in the presence of H2 have been measured in a combined shock tube laser-induced fluorescence experiment at temperatures from 440 to 690°K and 295°K.
Abstract: The vibrational relaxation times of DF(v = 1) in the presence of H2 have been measured in a combined shock tube laser‐induced fluorescence experiment at temperatures from 440 to 690°K and 295°K. The data fall along an extrapolation of previously obtained high temperature shock tube data. Data are presented also for the relaxation of HF(v = 1) by H2 and DF(v = 1) by D2.
TL;DR: In this paper, the AEDC-VKF Tunnel J with and without magnetohydrodynamic (MHD) flow augmentation is presented, and a full-scale, impulse-heated, high performance driver using helium and nitrogen was developed (concurrently but not in conjunction with the MHD shock tunnel).
Abstract: Experimental and theoretical studies conducted in support of the development of a high performance, hypersonic/hypervelocity shock tunnel facility (AEDC-VKF Tunnel J) capable of providing thermochemical equilibrium and nonequilibrium flow conditions at high enthalpies are presented. Demonstrated capabilities of the facility with and without magnetohydrodynamic (MHD) flow augmentation are shown. Increases in the flow velocity from 12,000 to 21,000 fps were obteined using an MHD nozzle accelerator with the flow seeded with potassium carbonate. Good agreemerit is shown to exist between one-dimensional MHD theory and experimental data for two calibrated conditions. Calibration and analysis of the flow in the MHD accelerator channel and in a twostage nozzle system, with and without MHD augmentation, are included. It is shown that quantitative aerodynamic measurements can be obtained in an MHD-augmented shock tunnel facility. A full-scale, impulse-heated, high performance driver (p/sub 4/ = 44,000 psi, T/sub 4/ = 800 deg K) using helium and nitrogen was developed (concurrently but not in conjunction with the MHD shock tunnel) and experimental shock tube data are presented. Projected capabilities of the facility using the high performance driver are included.
TL;DR: In this paper, a theoretical and experimental study was conducted on the performance of a 2.54 cm-diam shock tube driven by a 20 cmdiam hemispherical implosion driver.
Abstract: Implosions were used to raise the pressure and temperature of a driver gas to extreme values. Strong planar shock waves were thereby generated. A theoretical and experimental study was conducted on the performance of a 2.54-cm-diam shock tube driven by a 20-cm-diam hemispherical implosion driver. The analytical performance of the shock tube was predicted by numerically solving the set of governing nonlinear partial differential equations including appropriate loss mechanisms in the different regimes of the flow. The actual performance of the shock tube was determined experimentally by monitoring the shock velocity, flow uniformity, and test time for different driver conditions. These included stoichiometric hydrogen-oxygen mixtures with and without a PETN explosive liner. Planar shock waves were produced up to 11 km/sec without PETN and up to 19 km/sec with the addition of only 113 g of PETN explosive. Uniform test times of about 2-1 / sec were available at a distance of 33 m from the diaphragm (where the shock velocities were now 9 and 14 km/sec).
TL;DR: In this article, a free-piston shock tunnel is used to calculate the initial dissociation rate of nitrogen flow over a wedge, and a detailed calculation of the flow field by an inverse method, starting from the measured shock shape, is performed.
Abstract: Experimental results for dissociating nitrogen flow over a wedge, obtained in a free-piston shock tunnel, are described. Interferograms of the flow show clearly the curvature of the shock wave and the rise in fringe shift after the shock associated with the dissociation. It is shown that the shock curvature at the tip of the wedge can be used to calculate the initial dissociation rate and that it is a more sensitive indication of the rate than can be obtained from fringe shift measurements under the prevailing experimental conditions. Because the freestream dissociation fraction can be adjusted in the shock tunnel, the dependence on atomic nitrogen concentration of the dissociation rate can be determined by the shock curvature method. A detailed calculation of the flow field by an inverse method, starting from the measured shock shape, shows good agreement with experiments.
TL;DR: In this paper, the Particle-In-Cell (PIC) method has been adapted to handle suspension flows by treating each phase as a set of discrete "mass points," and phase interactions are incorporated into the equations for the changes in the properties of the materials occupying the cells.
Abstract: Theme T use of shock tubes for experimental investigations of high-speed suspension flows has motivated the development of a corresponding numerical calculation procedure. The Particle-In-Cell (PIC) method has been adapted to handle suspension flows by treating each phase as a set of discrete "mass points." As in the single-phase PIC calculation the flowfield is divided into small regions fixed in space (cells), but in the modified procedure phase interactions are incorporated into the equations for the changes in the properties of the materials occupying the cells. Details of the calculation are given in Ref. 2. The purpose of this study was to investigate the dependence of the calculated results on the assumed phase interaction (drag and heat transfer). The behavior of suspension flows in shock tubes also was investigated for the limiting case of problem times that are large compared with the characteristic velocity and thermal equilibration times. In this case, there exists a zone behind the shock within which the phases are in velocity and thermal equilibrium. These equilibrium properties, as well as the equilibrium shock speed, can be calculated by applying the shock tube equations to an "equivalent gas" defined in terms of the properties of the suspension, thereby providing a check on the calculated flow properties.
TL;DR: In this paper, the authors studied the thermal reactions of cyclopropane and cyclobutane behind reflected shock waves in a single-pulse chemical shock tube and compared their methods for obtaining reflected-shock temperatures and for estimating the extent of unimolecular fall-off.
Abstract: The kinetics of the thermal reactions of cyclopropane and cyclobutane behind reflected shock waves have been studied in a single-pulse chemical shock tube. Comparisons of methods for obtaining reflected-shock temperatures and for estimating the extent of unimolecular fall-off are presented.In the temperature range 950–1653 K, the predominant reaction of cyclopropane is the unimolecular isomerization to propene. Fully-corrected first-order rate constants are in good agreement with extrapolated low-temperature literature data up to ca. 1130 K, but at higher temperatures, previously reported curvature in the Arrhenius plot is confirmed.Between 891 and 1400 K, cyclobutane decomposes unimolecularly giving ethylene as the only observable product. Fully-corrected first-order rate constants for this reaction are also in agreement with extrapolated low-temperature literature data up to ca. 1080 K but pronounced curvature in the Arrhenius plot is evident above this temperature. Possible explanations for these anomalies above ca. 1100 K are discussed.
TL;DR: In this paper, the authors studied the variation of the stress required to induce fracture with crack length and found that an equation similar to the Griffith relationship applies over the range of crack lengths 38 mm>2c>16 mm, the surface energy value required to fit the Griffith type equation to the experimental data in this crack length range being similar to that derived from quasistatic testing of the same material.
Abstract: Thin walled cylindrical specimens of poly(methylmethacrylate) containing artificial flaws of different length and machined along a generator of the cylinder, are subjected to internal pressure pulses (shock pulses) of increasing magnitude until fracture occurs. A shock tube is used to generate the shock pulse. The variation of the stress required to induce fracture with crack length is studied. It is found that an equation similar to the Griffith relationship applies over the range of crack lengths 38 mm>2c>16 mm, the surface energy value required to fit the Griffith type equation to the experimental data in this crack length range being similar to that derived from quasi-static testing of the same material. It is found that the range of applicability of the Griffith equation is determined by the magnitude of the fracture stress of the non-artificially flawed material at the particular strain-rate at which the test is conducted.
TL;DR: In this paper, a super-Alfvenic and supersonic flow in a plasma wind tunnel was studied experimentally and a standing shock wave was found downstream of the magnetic nozzle exit.
Abstract: A super‐Alfvenic and supersonic flow in a plasma wind tunnel were studied experimentally The wind tunnel was constructed for the studies of the magnetohydrodynamic shock waves and wakes, and has features such as quasisteady flow and low fluctuation level The Alfven Mach number MA and ion acoustic Mach number M covered in the present experiment are MA = 1−4 and M = 2−6 A standing shock wave was found downstream of the magnetic‐nozzle exit The shock wave is collision free and the normal of the wavefront is parallel to the magnetic field Macroscopic features of the shock wave were discussed with reference to the theoretical predictions of the magnetohydrodynamic and collision‐free shock waves
TL;DR: In this article, the authors measured the opening times of the diaphragm in a Hypersonic Shock Tube and the effects of the opening process on the trajectory of the wave.
Abstract: 3 Simpson, C. J. S. M, Chandler, T. R. D., and Bridgman, K. B., "Measurements of the Opening Times of Diaphragms in a Shock Tube and the Effects of the Opening Process on Shock Trajectories," Aero Rept. 1194, 1966, National Physical Lab., Teddington, Middlesex, England. 4 Drewry, J. E. and Walenta, Z. A., "Determination of Diaphragm Opening-Times and Use of Diaphragm Particle Traps in a Hypersonic Shock Tube," TN 90, 1965, University of Toronto, Institute for Aerospace Studies, Toronto, Canada. 5 Kirev, V. T., "On Motion of a Shock Wave During Noninstantaneous Opening of Diaphragm in Shock Tube," News of Academy of Science USSR, Technology Section, Mechanics and Mechanical Engineering, No. 6, 1962, pp. 144-146. 6 Sandeman, R. J. and Alien, G. H., "A Double Diaphragm Shock Tube for the 10-20 km/sec Range," Proceedings of the Eighth International Shock Tube Symposium, edited by J. L. Stollery, A. G. Gaydon, and P. R. Owen, Chapman and Hall, London, England, 1971. 7 Glass, I. I, Chan, S. K, and Erode, H. L., "Strong Planar Shock Waves Generated by Explosively-Driven Spherical Implosions," A1AA Journal, Vol. 12, No. 3, March 1974, pp. 367-374. 8 Chan, S. K., "An Analytical and Experimental Study of an Implosion-Driven Shock Tube," Rept. 191,1973, University of Toronto, Institute for Aerospace Studies, Toronto, Canada. 9 Weiss, V., ed., Aerospace Structural Metals Handbook, Vol. 1: Ferrous Alloys, Syracuse University Press, Syracuse, N.Y., 1963.
TL;DR: In this article, the ignition of ethylene-oxygen mixtures highly diluted with argon was studied in a shock tube by monitoring the emission from CH* and C2* or OH*, and the measurements covered the temperature range of 1400-2100 K at the C2H4/O2 ratios of 0.33-1.00.
Abstract: The ignition of ethylene-oxygen mixtures highly diluted with argon was studied in a shock tube by monitoring the emission from CH* and C2* or OH*. The measurements covered the temperature range of 1400–2100 K at the C2H4/O2 ratios of 0.33–1.00. From the observation of the CH*, C2*, and OH* emissions, a mechanism for the production of chemiluminescent species upon ethylene oxidation was briefly discussed, and from the observation of the induction period of the CH* emission, the following equation was found:logτ_CH[O_2]=-11.45+27.5×10^3/4.58T in units of s mol l−1, the rate-determining step being C2H3+O2→C2H3O+O.
TL;DR: In this article, the vibrational relaxation of fluorine in argon has been studied in the temperature range 500-1300°K behind incident shock waves, where a laser schlieren system utilizing a fast quadrant photodiode and difference amplifier was used to record density changes behind the shock waves.
Abstract: The vibrational relaxation of fluorine in argon has been studied in the temperature range 500–1300°K behind incident shock waves. A laser schlieren system utilizing a fast, quadrant photodiode and difference amplifier was used to record density changes behind the shock waves. Data from 10% and 20% fluorine in argon mixtures were reduced to relaxation times using the Blackman technique and relaxation times for pure fluorine, and fluorine infinitely dilute in argon deduced using a curve fitting technique. The fluorine‐fluorine and fluorine‐argon relaxation times, in μsec · atm, were found to be best described by ln(Pτ)F2–F2 = −6.972+65.20T−1/3,ln(Pτ)F2–Ar = −8.650+96.97T−1/3, where T is the temperature in degrees Kelvin. The results of this investigation agree well with the low temperature results of Shields for pure fluorine relaxation.
TL;DR: In this paper, an experimental investigation of the ignition of individual fuel drops after their interaction with an incident and a reflected shock wave near the end wall of a shock tube has been carried out.
Abstract: An experimental investigation of the ignition of individual fuel drops after their interaction with an incident and a reflected shock wave near the end wall of a shock tube has been carried out. The influence of the aerodynamic shattering of the fuel drop by the convective flow on the ignition characteristics has been examined by varying the drop-end wall separation distance. Data are presented which show the ignition delay times to be a function of the various experimental conditions encountered in this study. A comparison is made with previous investigations concerning the ignition of a liquid fuel drop due only to the interaction with an incident shock wave.
TL;DR: In this article, an experimental investigation of the initiation, transition and quasi-steady propagation of blast initiated cylindrical detonations in Methyl Acetylene, Propane, Prodadiene (MAPP)-air mixtures is described.
Abstract: An experimental investigation of the initiation, transition and quasi-steady propagation of blast initiated cylindrical detonations in Methyl Acetylene, Propane, Prodadiene (MAPP)-air mixtures is described. A sectored shock tube was employed which was originally designed to allow study of cylindrical shock, and homogeneous and heterogeneous detonation waves. Cylindrical blast waves were generated by firing of controlled amounts of a condensed explosive at the apex of the sector. Experimental data served to suggest the existence of three wave propagation regimes: subcritical energy regime, where decoupling of shock and reaction zone results in a reacting blast wave-type decay; the critical energy regime, where decoupling occurs but is followed by the re-establishment of a sub-Chapman-Jouguet condition, with an asymptotic strengthening to the C J state; and supercritical energy regime, where the initially overdriven detonation decays asymptotically to its CJ state. Threshold energy levels delineating the subcritical to critical energy regimes were established for a wide range of MAPP-air mixtures. Lean and rich limits for steady propagating detonation waves were also established. Comparisons made with the work of others reveal that these limits do not suffer from scale effects. The detonation velocity, when attained, displayed a definite dependence on blast wave energy with the higher energy runs giving reasonable agreement with theory. The measured transition distances from blast to detonation wave, nondimensionalized by the blast wave explosion length, compared satisfactorily with theoretical predictions.
TL;DR: In this article, the decay of OH-radical concentration after shock-initiated combustion of H2:O2:Ar = 10:1:89 mixtures were analyzed to give the rate constant 1 × 1015 cm6mol−2s−1 for the reaction H + H + Ar = H2 + Ar overthe temperature range 1300 to 1700 K.
Abstract: Shock tube experiments on the decay of OH-radical concentration after shock-initiated combustion of H2:O2:Ar = 10:1:89 mixtures were analyzed to give the rate constant 1 × 1015 cm6mol−2s−1for the reaction H + H + Ar = H2 + Ar overthe temperature range 1300 to 1700 K.