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.
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机译：为研究银河系宇宙射线对气溶胶和云的影响，建立了宇宙（云）项目的宇宙。实验在Cern（瑞士）的26.1m3罐中进行。在实验中，研究了采集电离辐射对H 2 SO 4颗粒形成和生长的影响。为了评估实验配置，使用耦合的多维计算流体动力学（CFD）粒子模型进行模拟实验。在模型中，计算耦合的气体/蒸气物种，温度，流速和颗粒性能，以研究云坦克内容物的混合状态和混合时间。仿真结果表明，在第一实验中使用的一个风扇配置可能不足以确保均匀的混合室。要正确混合罐，需要两个风扇和足够高的风扇速度。发现壁温和饱和度率的瞬时变化的1 / E响应时间是几分钟的约。还发现颗粒成核和生长，并发现颗粒颗粒（颗粒数，平均尺寸，假定的日志正态分布的标准偏差）的粒子数尺寸分布特性被发现分布在坦克的体积上类似于气体物种。
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