Abstract
In this paper, the dynamic evolution of nanoparticles in a turbulent Taylor–Couette flow was studied by means of a numerical simulation. The initial particle size was 200 nm, and the volume concentration was 1 × 10−5. The Reynolds-averaged N–S equation for Taylor–Couette flow was solved numerically using the realizable k-ε model combined with the standard wall function. The numerical result of the velocity distribution is in good agreement with the experimental results. Additionally, the dynamic equation for the particle number distribution function was solved numerically using the Taylor series expansion moment method (TEMOM). The variation characteristics of particle number density, diameter and polydispersity in the flow were analyzed. The results show that particle breakage is obvious in the region with strong vorticity due to the large shear strength, which leads to a significant change in the particle number density, diameter and polydispersity. Furthermore, the effects of the gap width between two cylinders and the Reynolds number on the distribution of the particle number density, size and polydispersity are discussed.
Highlights
Define a dimensionless particle number density M0 = m0 /m00, where m0 and m00 are the particle number density and initial particle number density, respectively. As it can be seen from the contour of M0 on the r-z plane in Figure 5, there is no obvious difference in the distributions of the particle number density when considering and not considering the particle breakage, i.e., the particle breakage is weak when taking the parameters of case 1 in showsstage, the change in Min
The standard deviation of the particle distribution, i.e., the particle polydispersity, increases with the increase in the gap width, which is attributed to the idea that, on the one hand, particle breakage is less likely to occur in the flow with a weaker shear when the gap is wider, and, on the other hand, the particles size increases continuously due to coagulation, and the size range of the particles becomes wider
The main conclusions are summarized as follows: (1) Particle breakage leads to an increase in the particle number density and a decrease in
Summary
Research on the variation characteristics of the particle number density, diameter and polydispersity, considering particle coagulation and breakage, under turbulent conditions is significant in applications. The mechanism of particle coagulation includes the Brownian motion of particles and the shear effect of turbulent flow, and which of the two factors is dominant dends on the particle size and turbulence intensity [3,4]. Processes 2021, 9, 1789 related to particle breakage in turbulent pipe flow and found that the breakup was slower in the pipe flow where the turbulent shear rate was lower than in the free jet zone. [10] on applied population balance modeling kinetics the fractal dimension and the number of primary particles on particle breakage and found including the effects of breakage on turbulent flow.
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