The distribution of stresses in rigid fractal-like aggregates in a uniform flow field

The distribution of stresses in rigid fractal-like aggregates moving in a uniform flow field was investigated for particle–cluster and cluster–cluster aggregates with fractal dimensions ranging from 1.7 to 2.3. The method of reflections was used to calculate the drag force on each monomer, while the internal inter-monomer interactions were calculated by applying force and torque balances on each primary particle. The stress distribution was found to be very dissimilar from that of the applied external forces. Although the highest external forces act on the monomers located at the periphery of the aggregate where the drag is more intense, the most stressed inter-monomer bonds are always located in the internal part of the aggregate. This phenomenon is a consequence of the structure of the studied fractal aggregates, which are made mainly of filaments of monomers: the stress generated by the external forces is propagated and progressively accumulated by such filaments up to their roots, which are situated in the inner part of the cluster. Such a behaviour is different from that exhibited by highly connected structures, in which the loads are absorbed locally by the structure and the largest stresses are normally found in the proximity of the highest applied external forces.

Interfacial normal forces in a settling aggregate: the filamentous structure of the cluster accumulates internal stresses in the inner region of the cluster.Figure optionsDownload high-quality image (53 K)Download as PowerPoint slideResearch highlights
► Internal stress is propagated and accumulated along the filaments of the structure.
► The most stressed bonds are located in the internal region of the aggregate.
► The structure of fractal aggregates enhances internal stress.