Numerical Study on the Coagulation and Breakage of Nanoparticles in the Two-Phase Flow around Cylinders

The Reynolds averaged N-S equation and dynamic equation for nanoparticles are numerically solved in the two-phase flow around cylinders, and the distributions of the concentration M(0) and geometric mean diameter d(g) of particles are given. Some of the results are validated by comparing with previous results. The effects of particle coagulation and breakage and the initial particle concentration m(00) and size d(0) on the particle distribution are analyzed. The results show that for the flow around a single cylinder, M(0) is reduced along the flow direction. Placing a cylinder in a uniform flow will promote particle breakage. For the flow around multiple cylinders, the values of M(0) behind the cylinders oscillate along the spanwise direction, and the wake region in the flow direction is shorter than that for the flow around a single cylinder. For the initial monodisperse particles, the values of d(g) increase along the flow direction and the effect of particle coagulation is larger than that of particle breakage. The values of d(g) fluctuate along the spanwise direction; the closer to the cylinders, the more frequent the fluctuations of d(g) values. For the initial polydisperse particles with d(0) = 98 nm and geometric standard deviation σ = 1.65, the variations of d(g) values along the flow and spanwise directions show the same trend as for the initial monodisperse particles, although the differences are that the values of d(g) are almost the same for the cases with and without considering particle breakage, while the distribution of d(g) along the spanwise direction is flatter in the case with initial polydisperse particles.