NUMERICAL STUDY ON THE GROWTH PROCESS OF SECONDARY AEROSOL IN THE FOG

The collision and coagulation between aerosols are the dynamical base for migration and growth of aerosols in the fog. Based on the particle population balance equation and multi-Monte Carlo method, a numerical study on growth process of liquid secondary aerosol was carried out. The influence of flow turbulence and brown mechanisms on secondary aerosol collision and coagulation was analyzed for the initial monodispersal and exponential distribution. The computed results show that collision and coagulation between aerosols lead to the aerosol number decreased gradually, and the average volume of aerosol increased gradually. For the initial scale of free molecular area and monodispersal aerosols, when brown movement time is up to 600 s, the average volume of aerosol is increased to about 202.7 times of the initial, but its number is decreased to 0.006 of the initial. Considering the turbulent effect and brown motion, during the short period (100 s), secondary aerosol particle size is increased to 163 times of the initial, and its number is decreased to 0.025 times of the initial. The above phenomena illustrate that flow turbulence can cause strong transport and accumulation of aerosols, which lead to raise probability of aerosol collision and coagulation, and to increase aerosol scale gradually.