A rough scheme for radioactive dust particle capture by rain droplets is presented. Processes taking place both within the cloud with regular updrafts and in the layer of the atmosphere below the cloud that lead to a definite distribution of specific radioactivity with droplet size are considered. Comparison of experimental data on the fission‐product concentration in raindrops of different sizes with theoretical calculations allowed determination of the coefficient of rainout for removal of radioactive particles by cloud drops σ0 ∼ 10−3 sec−1, corresponding to an inverse proportionality between concentration and cloud drop radius. The functional dependence obtained theoretically is in good agreement with the experimental data. The influence of the specific radioactivity distribution versus droplet size on the variation of the specific radioactivity during a short‐range shower is considered.
The presented research demonstrates the results of a series of numerical simulations of gas flow through a single-stage centrifugal compressor with a vaneless diffuser. Numerical results were validated with experiments consisting of eight regimes with different mass flow rates. The steady-state and unsteady simulations were done in ANSYS FLUENT 13.0 and NUMECA FINE/TURBO 8.9.1 for one-period geometry due to periodicity of the problem. First-order discretization is insufficient due to strong dissipation effects. Results obtained with second-order discretization agree with the experiments for the steady-state case in the region of high mass flow rates. In the area of low mass flow rates, nonstationary effects significantly influence the flow leading stationary model to poor prediction. Therefore, the unsteady simulations were performed in the region of low mass flow rates. Results of calculation were compared with experimental data. The numerical simulation method in this paper can be used to predict compressor performance.
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