Cluster-Induced Deagglomeration in Dilute Gravity-Driven Gas-Solid Flows of Cohesive Grains.

Area of Science:

• Physics
• Granular Mechanics
• Fluid Dynamics

Background:

• Particle clustering is typically assumed to increase agglomeration due to reduced intra-cluster particle velocities.
• Previous studies on gas-solid flows often focus on noncohesive grains or lack detailed analysis of cohesive agglomerate formation.

Purpose of the Study:

• To investigate the relationship between clustering and agglomeration in gravity-driven, gas-solid flows of cohesive grains.
• To identify and explain the novel mechanism of "cluster-induced deagglomeration."

Main Methods:

• Discrete-particle simulations of dilute gas-solid flows with cohesive grains.
• Isolation of cohesive agglomerates from hydrodynamic clusters.
• Development of a theoretical model balancing agglomerate generation and breakage rates.

Main Results:

• Observed enhanced clustering with increasing system size, contrary to expectations for cohesive grains.
• Demonstrated reduced agglomeration with increased clustering, attributed to higher inter-region impact velocities.
• Validated the cluster-induced deagglomeration mechanism through simulations and theoretical modeling.

Conclusions:

• Clustering in cohesive granular flows can lead to deagglomeration, increasing granular temperature.
• This mechanism explains the saturation of agglomeration levels with increasing cohesion in gravity-driven systems.
• The interplay between cohesion, clustering, and deagglomeration is crucial for understanding granular flow dynamics.