Particle Velocity Data Research Articles

Shock compression data for liquids. I. Six hydrocarbon compounds

Dynamic high pressure equation-of-state data are reported for 1,3- and 1,4-cyclohexadiene, cyclohexene, cyclohexane, toluene, and n-hexane initially in the liquid state. Plane shock waves generated by high explosives produced pressures of 0.5 to 43.0 GPa and densities to twice normal density. Toluene and n-hexane exhibit transformations at 12.6 and 19.0 GPa, respectively, but cyclohexadiene, cyclohexene, and cyclohexane do not. Decomposition of the molecule is the probable cause for the transition. Results indicate that reducing the number of double bonds by adding hydrogen pairs to the benzene molecule causes the transition to disappear. The shock velocity−particle velocity (us −Up) data for toluene, toluene, cyclohexadiene, and n-hexane are best represented by one or more line segments while cyclohexene and cyclohexane are fit by a quadratic in particle velocity. An extrapolation of the Us−Up curves to zero particle velocity result in a Us value for each liquid that is approximateley 40% higher than the bulk sound speed. The specific volume at a particular pressure for these liquids is ordered such that the hydrocarbon with the larger hydrogen-to-carbon ratio has a larger specific volume. This behavior is similar to that observed for other hydrocarbons.

STEEP DIP FINITE‐DIFFERENCE MIGRATION*

AbstractA method is presented to derive approximate versions of the wave equation which allow finite‐difference migration for very steep dips (> 50°). It is shown that for conventional finite‐difference schemes, in addition to the dip limitation, the maximum acceptable frequency should be specified. A finite‐difference migration technique is proposed in the frequency domain. It is derived that finite‐difference wave field extrapolation in the frequency domain consists of a space‐variant convolution procedure for each frequency component, the space‐variance being defined by the lateral variation in the velocity.Finally it is shown that with finite‐difference migration, particle velocity data can be easily obtained from pressure data.

Solar wind electric field modulation in the interplanetary sector structure

The solar wind electric field near the earth has been computed for ∼4½ solar rotations, utilizing Heos 2 magnetometer and particle velocity data. A clear modulation is apparent as a function of the earth's position within interplanetary sectors. The electric field rises sharply at each sector boundary from a preboundary value of ∼ 1 mV/m to peak values between ∼3 mV/m and ∼6 mV/m. A correlation is found with several phenomena in the polar cap ionosphere.

Surface strong motion associated with a stick-slip event in a foam rubber model of earthquakes

Abstract In this paper, we present and interpret dynamic displacement data for a stick-slip event in a foam rubber model of earthquake faulting. Static displacement data are used to infer the stress drop of about 0.016 μ, where μ is the shear modulus. The rupture velocity 0.7 β, where β is the shear-wave speed, is also inferred from the data. The observed particle displacement and particle velocity data are compared with analytical and numerical predictions. Doppler focusing of energy by rupture propagation is clearly observed. No large transverse displacement pulse such as that observed at Station 2 of the Parkfield earthquake is observed. In addition to its value for testing analytical and numerical predictions, the laboratory model provides much needed information on the distribution of strong ground motion in the neighborhood of a fault and thus helps in the problem of microzonation for earthquakes.

Experimental analysis of spherical wave propagation

Analyses coupling in-material stress and particle velocity gage measurements with the equations of hydrodynamic flow are presently used for determining stress-volume paths during transient one-dimensional plane wave propagation in solids. In this work a method is described that allows analysis of attenuating experimental wave profiles of arbitrary shape in spherically symmetric flow. The method is applied to radial stress and particle velocity data for spherically divergent wave propagation in Westerly granite. The resulting relations among pressure, volume, and deviatoric stress are compared and are found to be consistent with other available data on Westerly granite. It is concluded that the analysis promises to be a useful tool for relating observed wave structure to physical processes occurring in the material and for developing better constitutive relations to predict the transient dynamic behavior of material.

An experimental study of the effects of prestrain on the propagation of small disturbances in neoprene filaments

A small disturbance was caused to propagate along a long, slender, prestrained Neoprene filament. The particle velocity of the pulse was measured at two stations along the length of the filament by means of electromagnetic transducers which operate on the Faraday principle. Particle velocity vs. time data were obtained from oscilloscope photographs of the transducer outputs for each level of prestrain from 0 percent up to 400 percent engineering strain. The two particle-velocity records for each level of prestrain were subjected to linear viscoelastic analysis which employed the use of numerical Fourier transforms of the particle-velocity records. Computer programs were written which allowed computation of the numerical transforms and from them the computation of the phase velocity and attenuation coefficients of the material over the narrow frequency bandwidth of the Fourier spectra of the particlevelocity pulses. Data analysis revealed that, at a given frequency, the phase velocity increases significantly and that the attenuation coefficient decreases significantly with an increase in prestrain level over the range of prestrains of the tests.

Photomicroscopic Sublayer Velocity Measurement

The measurement of velocity in the boundary layer region can be a difficult problem using probes. The use of a microscope to observe the motion of small tracer particles can yield quantitative velocity data without disturbing the flow. The application of this technique to turbulent open channel flow is described. Micron particles which act as indicators of the instantaneous velocity vector were photographed through a microscope as they passed through the focal field which was oriented parallel to the channel bottom. By varying the location of the field, a profile normal to the bottom was obtained. The high speed motion picture film was analyzed to obtain particle velocity data which was in turn used to compute a mean velocity profile, turbulence intensity and skewness of the particle velocity distribution. It is pointed out that due to uncertainty of particle location within the focal field, errors in the computation of mean velocity and turbulence intensity can arise. These errors are analyzed quantitatively.

Turbulent convective heat and mass transfer from accelerating particles

AbstractThe rate of evaporation of acetone from single particles accelerating freely in a downward concurrent turbulent air stream was studied over a range of air velocities from 40 to 70 ft./sec. and at a constant air temperature of 410°F. The particles consisted of celite in the shape of spheres, cubes, disks and cylinders, varying in size from 0.15 to 0.40 in. Accurate particle velocity data were obtained with a new radioactive tracer technique, and high‐speed photography at two positions along the column permitted measurement of the rate of rotation and showed that the particles rotated in a random manner.Adequate prediction of the observed heat and mass transfer data could be obtained from the integration of a rate eequation previously reported for stationary particles. The concept of a new characteristic dimension, developed for the latter case, was found to be applicable to randomly rotating shapes and to account satisfactorily for the behaviour of nonspherical particles.

Application of the Engravement Method to the Study of Particle Velocity Distribution in Explosively Loaded Cylinders

Application of the engravement method to the study of particle velocity distribution in the wall of a thick-walled metal cylinder internally loaded with an explosive charge is described. Tests were conducted with this method on modified cylinders of annealed low-carbon steel and of brass. Even though each of the modified cylinders broke into a number of fragments, the engravements were well enough preserved to furnish considerable data. Many measurements were obtained from each cylinder by using a large number of pellets of several thicknesses. Particle velocity data were obtained to within 716 inch from the metalexplosive interface. Temporal particle velocity distribution curves are presented for each of the cylinders.