关键词: nanoparticle, coagulation, turbulent, pipe flow

Abstract: Numerical simulations of nanoparticle migration in a fully developed turbulent pipe flow are performed. The evolution of particle number concentration, total particle mass, polydispersity, particle diameter and geometric standard deviation is obtained by using a moment method to approximate the particle general dynamic equation. The effects of Schmidt number and Damköhler number on the evolution of the particle parameters are analyzed. The results show that nanoparticles move to the pipe center. The particle number concentration and total particle mass are distributed non-uniformly along the radial direction. In an initially monodisperse particle field, the particle clusters with various sizes will be produced because of coagulation. As time progresses, the particle cluster diameter grows from an initial value at different rates depending on the radial position. The largest particle clusters are found in the pipe center. The particle cluster number concentration and total particle mass decrease with the increase of Schmidt number in the region near the pipe center, and the particles with lower Schmidt number are of many dif-ferent sizes, i.e. more polydispersity. The particle cluster diameter and geometric standard deviation increase with the increase of Damköhler number at the same radial position. The migration properties for nano-sized particles are different from that for micro-sized particles.

Key words: nanoparticle, coagulation, turbulent, pipe flow