Experimental study of the effect of artificial charged aqueous aerosol cloud on model aircraft radome

The effect of artificial clouds of strongly charged aqueous aerosol on model aircraft radomes has been experimentally studied. It is established that the character of discharge development in the “charged aerosol cloud-inner electrode under model radome” gap significantly differs from that observed in the absence of the model radome. The presence of the dielectric radome in the gap between charged cloud and ground can lead to the phenomenon of reversal of the polarity of discharge current from the electrode (modeling antenna). Dependence of the discharge development and its characteristics on the size (volume) of space under radome has been studied. Possible physical mechanisms involved in the interaction of lightning discharges and thunderstorm clouds with radiotrasparent aircraft radomes and equipment arranged inside are considered.     

Breakdown of model aircraft radome dielectric shell in artificial charged aerosol clouds

The breakdown of a model aircraft radome dielectric shell in artificial charged aqueous aerosol clouds has been experimentally studied. It is established that, in most cases, electric breakdown of a model shell takes place without explicit discharge development between a charged aqueous aerosol cloud and a model antenna arranged under the radome shell. The probabilities of the dielectric shell breakdown have been determined for various radome models. A possible mechanism of the shell breakdown in hollow dielectric radomes interacting with charged aqueous aerosol clouds and electric discharges in these clouds is proposed that takes into account the accumulation of charges of opposite signs on the internal and external surface of the radome.     

Laser heating of an aqueous aerosol particle

Approximate analytical and full numerical solutions are obtained for the transient response of both a pure water and solution droplets to both short- and long-time laser heating. The differences in the temperature and size histories between pure water and solution droplets are elucidated. The validity of of the approximate analytical solution, extended from that of Armstrong ["Aerosol Heating and Vaporization by Pulsed Light Beams," Appl. Opt. 23, 148 (1984)] in pure water droplets, is evaluated by comparison to solution of the full governing equations.     

The interaction of charged planes in an electron cloud and plasma

Distributions of the field potential, the field intensity, and the plasma density are considered for charged planes surrounded by thermoemission electrons, compensating the charge of these planes, or by a finite-density plasma. It is shown that the planes in both cases repulse each other due to the action of electrostatic forces. An expression for the electrostatic pressure is derived.     

Vacuum discharge as an effective source of multiply charged ions

The time-of-flight (TOF) spectra measured under high vacuum conditions revealed ion beams of a cathode material (Cu ⁿ⁺) with a maximum charge of up to +19 generated in the initial stage of a spark discharge development at a storage voltage of up to U ₀=2.5 kV. As the U ₀ value increases, the range of the multiply charged states of ions detected by the TOF technique increases, the average ion charge reaching +9.     

A physical mechanism of dense smoke suppression in a closed room by admitting a charged aqueous aerosol

It is experimentally demonstrated that the rapid suppression of an optically dense aerosol (smoke) by a strongly charged aqueous aerosol is related to acceleration of the volume diffusion and to electrostatic repulsion of the charged agglomerates.     

The evolution of an aerosol cloud under conditions of diffusion mixing with gas

The one-dimensional problem of mixing of aerosol with gas, accompanied by phase transitions, is solved in a self-similar formulation. The evolution of temperature and concentration fields is studied as a function of the initial temperatures of aerosol and gas, as well as of the particle density of vapor in gas. The options are analyzed of mixing of aerosol with cold and warm gas, as well as with superheated vapor.     

Simultaneous estimation of aerosol cloud concentration and spectral backscatter from multiple-wavelength lidar data

We present a sequential algorithm for estimating both concentration dependence on range and time and backscatter coefficient spectral dependence of optically thin localized atmospheric aerosols using data from rapidly tuned lidar. The range dependence of the aerosol is modeled as an expansion of the concentration in an orthonormal basis set whose coefficients carry the time dependence. Two estimators are run in parallel: a Kalman filter for the concentration range and time dependence and a maximum-likelihood estimator for the aerosol backscatter wavelength and time dependence. These two estimators exchange information continuously over the data-processing stream. The state model parameters of the Kalman filter are also estimated sequentially together with the concentration and backscatter. Lidar data collected prior to the aerosol release are used to estimate the ambient lidar return. The approach is illustrated on atmospheric backscatter long-wave infrared (CO2) lidar data.     

Generation of aerosol nanoparticles by the multi-spark discharge generator

We have experimentally studied the formation of aerosol nanoparticles synthesized by the processes of electro-erosive wear of three pairs of electrodes upon a series connection on the discharge circuit that is controlled by a frequency generator of pulsed currents. Using a diffusion aerosol spectrometer, we have measured the particle-size distribution in the flows of aerosols upon varying velocity V of air flow, repetition frequency of discharge f, and single discharge energy W. It has been established that when controlling parameters of generator one can obtain nanoparticles (agglomerates of nanoparticles) in a wide range of mean size values d _mean from 8 to 75 nm with a geometric standard deviation (GSD) of 1.3–2.0. The growth of agglomerates of nanoparticles monotonously depends on the residence time of particles in the gas and the particle concentration.     

Effect of an electric field on the discharge of polydispersions from a slotted vertical plane-parallel channel

Results are shown of an experimental study concerning electrorheological dielectric systems and the hydrodynamic characteristics of their discharge from a slotted plane-parallel channel in the presence of a constant electric field.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 23, No. 4, pp. 681–685, October, 1972.     

Generalization of an asymptotic model for constant-rate aerosol reactors

An asymptotic model was previously developed to predictbehaviors of constant-rate aerosol reactors operating with particles in the free-molecular or continuum limits. This model considered the limiting cases of having either condensation or nucleation dominate during a nucleation burst that occurs from steady addition of condensable monomer. In the present article, this model is generalized to allow condensation and nucleation to both be important during a nucleation burst. Criteria are derived to predict the relative magnitudes of nucleation and condensation, and scaling relations are presented for particle number densities, particle sizes, and onset times and durations of nucleation bursts. Comparison of the asymptotic results with numerical integration of the governing equations is favorable both qualitatively and quantitatively.     

Parameterization of aerosol and cirrus cloud effects on reflected sunlight spectra measured from space: application of the equivalence theorem

An original methodology to account for aerosol and cirrus cloud contributions to reflected sunlight is described. This method can be applied to the problem of retrieving greenhouse gases from satellite-observed data and is based on the equivalence theorem with further parameterization of the photon path-length probability density function (PPDF). Monte Carlo simulation was used to validate this parameterization for a vertically nonhomogeneous atmosphere including an aerosol layer and cirrus clouds. Initial approximation suggests that the PPDF depends on four parameters that can be interpreted as the effective cloud height, cloud relative reflectance, and two additional factors to account for photon path-length distribution under the cloud. We demonstrate that these parameters can be efficiently retrieved from the nadir radiance measured in the oxygen A-band and from the H(2)O-saturated area of the CO(2) 2.0 microm spectral band.     

Effect of dicationic ionic liquids on cloud points of tergitol surfactant and the formation of aqueous micellar two-phase systems

Journal of Materials Science - A cloud point evaluation was performed for the nonionic surfactant Tergitol 15-S-7 in aqueous solutions of McIlvaine buffer (pH 7.0). Cloud point temperatures of the...     

Magnetogasdynamic model of capillary discharge from evaporating wall

The article describes the mathematical and physical models of heavy-current capillary discharges. The results of numerical calculation of plasma flow in capillaries are presented.     

Effect of an electrostatic field on the optical properties of a cloud of dielectric particles

The optical properties of a cloud of anisotropic dielectric particles when the orientational distribution is made nonrandom by interaction with an electrostatic field are studied. Since the interaction energy is determined by the polarizability of the particles, a general expression for the polarizability of nonspherical particles is worked out. In particular, we investigated the response to the electrostatic field of two different dispersions whose component particles are built as clusters of four identical spheres. Although in one cloud the clusters were shaped as linear chains, and in the other cloud the clusters were shaped as squares, the optical properties of both dispersions as a function of the static field are rather similar. There are, however, noticeable ranges of size within which the optical response of the two kinds of particles is substantially different.     

Effect of ultrasonic vibration on the single discharge of electrochemical discharge machining

Electrochemical discharge machining (ECDM) is one of the non-traditional processes which employs physical and chemical phenomena to remove the material from the non-conductive workpiece. Moreover, some technical augmentations have been added to the mentioned process to achieve a more efficient machining method. Typically, ECDM includes numerous electric discharges, but study on a single discharge, with/without application of external augmentation, leads to understanding the complicated nature of the ECDM process and the effect of technical augmentation. In this research, the ECDM process is studied in the mode of single discharge. Also, ultrasonic vibration, as a technical augmentation, is added to the process (UAECDM) and related effects are studied. For this purpose, special configuration and equipment are used to apply ultrasonic vibration and generate only single discharge. Material removal and tool wear are two important characteristics of drilling process which can be considered to determine the machining efficiency. The current signal is used to determine the current variation and discharge(s) condition. Results showed that the application of ultrasonic vibration changed the current signal pattern to increase discharge numbers in constant condition. Also, ultrasonic vibration increased the material removal up to 35%, while tool wear reduced between 3% and 14%.     

Optical pulsating discharge plasma dynamics in a supersonic jet: Experiment and an analytical model of the quasistationary flow development

An analytical method for determining the wave structure and quasistationary flow parameters of an optical pulsating discharge plasma expanding in a supersonic flow is developed. The method is based on a physical model of the optical gas breakdown, a theory of the point explosion, the results of numerical modeling of the breakdown plasma dynamics along a laser beam, experimental data, and numerical estimates.     

Effect of an impact-generated gas cloud on entrained surface boulders and spall ejecta

The purpose of this investigation is to study the effect of an impact-generated gas cloud on the size-velocity distribution of large, solid ejecta fragments that become entrained in it, with particular reference to the possible Martian origin of the SNC meteorites. The entrainment both of loose surface boulders and of the early-time, large-size, high-velocity spall component of the crater ejecta is modeled numerically. Surface boulders from as far as 40 km from the center of impact can be accelerated by the high velocity leading edge of the gas cloud to velocities in excess of Martian escape velocity (5 km/s), but are generally crushed by the acceleration. Spall fragments become entrained later and nearer the center of the gas cloud, where gas velocities are much less. High velocity spalls are decelerated by the gas and low velocity spalls are accelerated by the gas, but no spalls ejected at < 5km/s are accelerated to velocities 5km/s. An impact-generated gas cloud is thus expected to scour the pre-existing surface of loose material and to change the size-velocity distribution of spall ejecta, but does not sufficiently enhance the velocities of crater ejecta to explain the Martian origin of SNC meteorites as large rocks.     

Effect of the initial velocity of an aerosol on its trajectory in a curving gas stream

On the basis of an experimental and theoretical investigation, the authors analyze the effect of the initial velocity of an aerosol on its subsequent motion.