Modeling th dynamics of charged drop of one liquid in another under the action of an electric field

The work is devoted to the study of the features of the behavior of a group of droplets of one viscous liquid in another under the influence of various physical fields. When considering the dynamics of two drops under the action of an electric field, it is assumed that a drop in the form of a sphere with radius а will be placed in an electric field with an intensity , investigates how droplets will react to each other under the influence of an electric field. A mathematical model has been built and a computer program has been developed for the numerical solution of this problem. The behavior of several drops in an electric field is studied for different physical parameters of the material of the drops and the environment, as well as for different initial distributions of drops and the strength of the electric field. It is shown for the first time that emulsion droplets distributed in space, under the action of an electric field, begin to move and after a certain time a new stationary structure of droplets is formed. It was found that the relaxation time depends on the electric field strength, the size of the droplets and their initial distribution.

Effects of ionisation on cloud behaviour in planetary atmospheres

<p>Cosmic rays cause ionisation in all planetary atmospheres. As they collide with particles in the atmosphere, secondary charged particles are produced that lead to the formation of cluster ions. The incident cosmic ray flux and atmospheric density of the atmosphere in question determine a profile of ion production rate. From the top of the atmosphere to the planetary surface, this rate increases with atmospheric density to a point where the flux becomes attenuated such that the rate then decreases, resulting in a peak ion production rate at some height known as the Pfotzer-Regener maximum. When these ions interact with aerosols and cloud particles, a net charge results on those particles and this is known to affect their microphysical attributes and behaviour. For example, charging may enable the activation of droplets at lower saturation ratios and also enhance collision efficiency and droplet growth. This becomes important when clouds occur at a height where ionisation is sufficient to have a substantive charging effect on the cloud particles. This has very little direct effect on Earth as peak ion production occurs high above the clouds at 15-20 km; however, on Venus for example the Pfotzer-Regener maximum occurs at ~63 km, coinciding with the main sulphuric acid cloud deck. In situations such as this, the direct result of cloud charging due to cosmic ray induced ionisation may strongly influence cloud processes, their occurrence, and behaviour.</p><p>This work uses laboratory experiments to explore the effects of charging on cloud droplets. Individual droplets are levitated in a vertical acoustic standing wave and then monitored using a CCD camera with a high magnification objective lens to determine the droplet lifetime and evaporation rate. Experiments were conducted using both the droplets’ naturally occurring charge as well as some where the region around the drop was initially flooded with ions from an external corona source. The polarity and charge magnitude of the droplets was determined by applying a 10 kV/m electric field horizontally across the drop and observing its deflection towards one of the electrodes. Theory predicts that the more highly charged a droplet is, the more resistant to evaporation it becomes. Experimental data collected during this study agrees with this, with more highly charged droplets observed to have slower evaporation rates. However, highly charged drops were also observed to periodically become unstable during evaporation and undergo Rayleigh explosions. This occurs when the droplet evaporates until its diameter becomes such that its fissility reaches the threshold at which the instability occurs. Each instability of a highly charged drop removes mass, reducing the overall droplet lifetime regardless of the slower evaporation rate. Therefore, where enhanced ionisation occurs in the presence of clouds the end result may be to reduce droplet stability.</p>

Об устойчивости сильно заряженной капли, подвешенной в суперпозиции гравитационного и электростатического полей

For strongly charged drop suspended in a fixed status in superposition gravitational and electrostatic fields, critical conditions of realization of its instability in relation to own and induced charges are found. All calculations are carried out in the fourth order of smallness on value of stationary deformation of spherical shape of a drop and first order on the dimensionless amplitude of its capillary oscillations. Dependences of values of critical parameters of Rayleigh and Taylor on radius, density, coefficient of surface tension, acceleration of the field of gravity and from number of a mode of oscillations, other than those for the free drop are found. With increase mode number the critical value of parameter of Rayleigh grows and comes to an asymptotic , and the critical value of Taylor parameter decreases and comes to an asymptotic . The specified changes and are explained by existence of a condition of immobility of the center of masses in a suspension connecting , and acceleration of the field of gravity.