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Title: Numerical simulations of mixing conditions and aerosol dynamics in the CERN CLOUD chamber
Authors: Voigtländer, J.Duplissy, J.Rondo, L.Kürten, A.Stratmann, F.
Publishers Version: https://doi.org/10.5194/acp-12-2205-2012
Issue Date: 2012
Published in: Atmospheric Chemistry and Physics, Volume 12, Issue 4, Page 2205-2214
Publisher: München : European Geopyhsical Union
Abstract: To study the effect of galactic cosmic rays on aerosols and clouds, the Cosmics Leaving OUtdoor Droplets (CLOUD) project was established. Experiments are carried out at a 26.1 m3 tank at CERN (Switzerland). In the experiments, the effect of ionizing radiation on H2SO4 particle formation and growth is investigated. To evaluate the experimental configuration, the experiment was simulated using a coupled multidimensional computational fluid dynamics (CFD) – particle model. In the model the coupled fields of gas/vapor species, temperature, flow velocity and particle properties were computed to investigate mixing state and mixing times of the CLOUD tank's contents. Simulation results show that a 1-fan configuration, as used in first experiments, may not be sufficient to ensure a homogeneously mixed chamber. To mix the tank properly, two fans and sufficiently high fan speeds are necessary. The 1/e response times for instantaneous changes of wall temperature and saturation ratio were found to be in the order of few minutes. Particle nucleation and growth was also simulated and particle number size distribution properties of the freshly nucleated particles (particle number, mean size, standard deviation of the assumed log-normal distribution) were found to be distributed over the tank's volume similar to the gas species.
Keywords: aerosol; aerosol composition; computational fluid dynamics; experimental study; flow velocity; numerical model; particle motion; particle size; size distribution
DDC: 550
License: CC BY 3.0 Unported
Link to License: https://creativecommons.org/licenses/by/3.0/
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