Observations made in the CLOUD chamber at CERN illuminate atmospheric particle formation. How new particles form New particle formation in the atmosphere produces around half of the cloud condensation nuclei that seed cloud droplets. Such particles have a pivotal role in determining the properties of clouds and the global radiation balance. Dunne et al. used the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN to construct a model of aerosol formation based on laboratory-measured nucleation rates. They found that nearly all nucleation involves either ammonia or biogenic organic compounds. Furthermore, in the present-day atmosphere, cosmic ray intensity cannot meaningfully affect climate via nucleation. Science, this issue p. 1119 Fundamental questions remain about the origin of newly formed atmospheric aerosol particles because data from laboratory measurements have been insufficient to build global models. In contrast, gas-phase chemistry models have been based on laboratory kinetics measurements for decades. We built a global model of aerosol formation by using extensive laboratory measurements of rates of nucleation involving sulfuric acid, ammonia, ions, and organic compounds conducted in the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber. The simulations and a comparison with atmospheric observations show that nearly all nucleation throughout the present-day atmosphere involves ammonia or biogenic organic compounds, in addition to sulfuric acid. A considerable fraction of nucleation involves ions, but the relatively weak dependence on ion concentrations indicates that for the processes studied, variations in cosmic ray intensity do not appreciably affect climate through nucleation in the present-day atmosphere.

Global atmospheric particle formation from CERN CLOUD measurements

Investigation on the mechanism of water activated via tourmaline powder

As one of the emerging application areas of the corona discharge technique, rain enhancement induced by atmospheric air ionization has made a great breakthrough. Although natural rainfall modified by artificial ionization was successfully observed via the statistical data of field experiments, deficient efforts have been devoted to the research on the near-field effect of corona discharge on the evolution of water droplets around the discharge device. In this article, we studied the electrostatic effects of corona discharge on the spectrum and density evolution of water droplets in a 96-m3 cloud chamber. An interesting phenomenon was found that two different electrostatic effects appeared when various high voltages were applied on the corona electrode. In detail, the growth of droplets larger than $10~\mu \text{m}$ was detected once the applied high voltage exceeds the critical value (e.g. −80 kV in our discharge device), and this is attributed to the electrostatic induction effect. By contrast, a narrow droplet size spectrum and reduced density caused by the strong electrostatic precipitation effect were shown below this critical voltage. To figure out the mechanisms underlying these phenomena, the charging status of water droplets with various sizes, forces of charged droplets under various electric field strength, and collision kernels between droplets, are analyzed through theoretical calculations. Results show that the electric field plays a dominant role in the charging process of droplets and the acceleration of collision-coalescence between charged and neutral droplets, which results in the different electrostatic effects on the evolution of droplets. This article may provide some enlightenment to fog elimination in industrial application and cloud-seeding in atmospheric water resources comprehensive utilization.

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Electrostatic Effects of Corona Discharge on the Spectrum and Density Evolution of Water Droplets in Air

Microscopic stabilization mechanism of nanoparticle-laden droplets under external electric fields: A molecular dynamics study

Nanoscale charged water droplets play a significant role in many physical processes, including cloud electrification and electrospray ionization, which have become one research focus. Generally, the maximum value of charge that a droplet can carry is called Rayleigh limit. Here, we investigate the effect of electric field (<0.5 V nm−1) on Rayleigh limit of nanoscale water droplets (r < 5 nm) by molecular dynamics simulation and theoretically qualitative analysis. In the simulation, Rayleigh limit of nanoscale water droplets under various electric fields is investigated based on optimal point charge water model by GROMACS package code. Our study demonstrates that electric field could affect Rayleigh limit by generating the induced charge, changing the surface tension and the droplet shape. Further, we propose the modified Rayleigh limit formula under electric field, with considering the potential energy of deformed charged droplet under strong electric field. The modified formula can qualitatively explain the abnormal trend that Rayleigh limit of nanoscale water droplet (r > 3 nm) decreases first and then increases with the electric field (<0.5 V nm−1) in the simulation.

Effects of electric field on Rayleigh limit of nanoscale water droplets: molecular dynamics simulation

Combined effect of weak electric field and ions on critical water cluster: Insight from molecular dynamics simulation

The invention discloses a cooling system used for a tokamak device divertor and based on an evaporative cooling principle. The system comprises an external secondary cooling heat exchanger, an inlet liquid-collecting pipe, divertor internal pipelines and an outlet liquid-collecting pipe. The external secondary cooling heat exchanger is used to convey a liquid cooling medium to the inlet liquid-collecting pipe; the inlet liquid-collecting pipe is used to convey the liquid cooling medium to the divertor internal pipelines; the divertor internal pipelines are used to enable the entered liquid cooling medium to absorb heat and vaporize to form a cooling medium in a liquid-gas two-phase flow state; the outlet liquid-collecting pipe is used to convey the cooling medium in the liquid-gas two-phase flow state to the external secondary cooling heat exchanger; and the external secondary cooling heat exchanger is also used to make the cooling medium in the two-phase flow state release heat and become a liquid cooling medium again.

Cooling system used for tokamak device divertor and based on evaporative cooling principle

Charged particles are widely used in the fields of defogging, haze removal and artificial rainfall. A novel transport strategy of charged particles based on the vortex rings is presented in this paper, to expand the effective action region and enhance the effect of charged particles. Transport distance and transport velocity (TV) of charged particles are the crucial two evaluation indexes. For the vortex rings generated by a piston-cylinder device, the transport velocity is closely related to Reynolds number and formation time. Based on the k-ω turbulence model, this paper verifies the relationship between vortex ring circulation, transport velocity and Formation Number in air by finite element methods, and studies the influence on the formation of vortex rings of an insulating bell mouth placed at the outlet of cylinder. The simulation results show that the Formation Number of vortex rings in the air is 4.0 ~ 5.0, and the growth rate of transport velocity of vortex ring slows down when the formation time is larger than Formation Number. The study also indicates that the bell mouth has little effect on the velocity of the vortex ring, when the bell mouth angle is greater than 45° and the length of generatrix is between 0.2 m and 1.0 m. Therefore, the research results can provide a reference for the design and optimization of a vortex ring generator for transporting charged particles to a certain target area.

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Feng Han

Papers

Combined effect of weak electric field and ions on critical water cluster: Insight from molecular dynamics simulation

Cooling system used for tokamak device divertor and based on evaporative cooling principle

Numerical Analysis of Charged Particles Transport in Air Based on Vortex Rings

Effects of electric field on Rayleigh limit of nanoscale water droplets: molecular dynamics simulation