Research on bimodal particle extinction coefficient during Brownian coagulation and condensation for the entire particle size regime |
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Authors: | Hong Tang Jian-Zhong Lin |
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Institution: | (1) State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou, 310027, China;(2) College of Metrology & Measurement Engineering, China Jiliang University, Hangzhou, 310018, China; |
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Abstract: | The extinction coefficient of atmospheric aerosol particles influences the earth’s radiation balance directly or indirectly,
and it can be determined by the scattering and absorption characteristics of aerosol particles. The problem of estimating
the change of extinction coefficient due to time evolution of bimodal particle size distribution is studied, and two improved
methods for calculating the Brownian coagulation coefficient and the condensation growth rate are proposed, respectively.
Through the improved method based on Otto kernel, the Brownian coagulation coefficient can be expressed simply in powers of
particle volume for the entire particle size regime based on the fitted polynomials of the mean enhancement function. Meanwhile,
the improved method based on Fuchs–Sutugin kernel is developed to obtain the condensation growth rate for the entire particle
size regime. And then, the change of the overall extinction coefficient of bimodal distributions undergoing Brownian coagulation
and condensation can be estimated comprehensively for the entire particle size regime. Simulation experiments indicate that
the extinction coefficients obtained with the improved methods coincide fairly well with the true values, which provide a
simple, reliable, and general method to estimate the change of extinction coefficient for the entire particle size regime
during the bimodal particle dynamic processes. |
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Keywords: | |
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