Hydrodynamics of inhomogeneous agglomerates for a fractal dimension of 2.5 at intermediate Reynolds numbers: Effect of agglomerate sizes and Reynolds numbers

Abstract

In this study, the effect of agglomerate sizes for a fractal dimension (D f ) of 2.5 on the hydrodynamics at intermediate Reynolds numbers (Re) of 1-120 was assessed. The results show that a core behaves like a solid sphere that exists in the central region inside the agglomerate. In addition, increasing the agglomerate diameter represents adding an extra permeable layer outside the agglomerate. For a larger Re or a smaller agglomerate diameter, the fluid can enter and penetrate through the agglomerate more easily, and the hydrodynamic characteristics of agglomerates deviate more from those of solid spheres. The effect of diameters on the velocity and pressure profiles becomes less significant with the increase in the diameter. Based on the simulated results, the drag ratio has an approximately linear relationship with Re, and its intercept has an exponential relationship with the dimensionless agglomerate diameter. Compared with homogeneous porous spheres, the drag ratio of the agglomerate is different. The effect of diameters on the drag ratio decreases as the diameter increases. It should be noted that the effect of radially varying permeability on inhomogeneous agglomerates should not be ignored and that the effect weakens as Re increases.

Shielding Effect of Fractal Nanoparticle Agglomerates Aligned Streamwise

“…This demonstrates that there is a solid-like central core inside FNPAs when considering RVPM. Previous studies ,,− have reported that agglomerates that follow the particle-cluster regime have a relatively dense core structure. This solid-like central core results in a greater velocity attenuation as the fluid passes through.…”

“…The complex structure inside nanoparticle agglomerates is difficult to describe by standard (Euclidean) geometry . However, it has been reported in recent years that some nanoparticle agglomerates formed by the particle-cluster regime have fractal characteristics, ,,,,, and the structure within nanoparticle agglomerates is typically described in terms of fractal geometry. As shown in Figure , based on the fractal theory, nanoparticle agglomerates in this regime are claimed to be formed by smaller particles adding to the exterior of a “seed” agglomerate and its local porosity averaged over the length scale will vary with the radial distance .…”

“…Most of the above simulations about FNPAs focused only on the condition for Re ≪ 1. However, Re of FNPAs may reach up to tens or hundreds in industrial applications such as fluidization, pneumatic conveying, and free settlement for FNPAs. , To better align with actual industrial applications, our extensive preliminary works − have extended the applicability of the RVPM to study the hydrodynamics of FNPAs at medium to high Re , but it is limited to individual FNPAs. In this study, RVPM is further considered for the study of hydrodynamic interactions between FNPAs at medium to high Re .…”