Three-dimensional simulation for perikinetic flocculation of fine sediment under the ionization in still water

摘要

A simulation based on Brownian dynamic for perikinetic flocculation of fine sediment under the ionization is presented. The Langevin equation is used as dynamical equation for tracking each particle making up a floe. Monte Carlo method was used for simulate random variation in particle movement. An initial condition and periodic boundary condition which conformed to reality well is used for calculation. In each cell 1000 particles of 10ìm, 15ìm, 20ìm, 25ìm, 30ìm in diameter were served as primary particles. Floe growth is based on the thermal force and the electrostatic force. The electrostatic force on a particle in the simulation cell is considered as a sum of the electrostatic force from other particles in the original cell. The particles are supposed to be motion with uncharged and charged state in dispersion system. A comparison of the initial flocculent time and smashing time in sludge density 1010kg/m~3, 1025 kg/m~3, 1050 kg/m~3, 1075 kg/m~3, 1100 kg/m~3 were present to show the effect of it on floe growth. The increase of sludge density deferred the flocculation rate. To study morphological shape of floe, the radius of gyration was revealed under different situations. On one hand the radius of gyration presented random variation with uncharged particle, On the other hand, the radius of gyration increases gradually with the increase of polar electrical charges on primal particle. Moreover, the morphological shape for the charged floe was more open than that of unchanged state. Finally, a series of experimental results are present, which is coincide with model well.