&Bullet; physics 14, p42

Cubes suspended in a liquid are less likely than spheres to cluster and fall out of solution.

A. Seyed-Ahmadi and A. Wachs [1]

Particulate-laden currents are ubiquitous in natural and industrial processes. Models that describe how particles behave in a suspension are, among other things, of decisive importance for the explanation of river deposits and the planning of sewage treatment plants. However, these models assume that particles are spherical. This is a problem in a world where grains of sediment come in all shapes and sizes. Arman Seyed-Ahmadi and Anthony Wachs from the University of British Columbia, Canada, are now using simulations to show that a cube-laden flow, in contrast to a spherical flow, tends to resist clustering and to remain homogeneous for longer. The result provides an important update for models of environmental flows.

Seyed-Ahmadi and Wachs developed numerical simulations that take into account the hydrodynamic forces and torques experienced by hundreds of cubic particles suspended in a water tank. The simulations track the velocity fluctuations of the particles, the resulting microstructure of the suspension and the forces on each particle. The duo found that the spatial distribution of the cubes is more homogeneous than a similar mixture of spheres.

This result comes from the sharp edges of the cubes, which create rotational buoyancy forces that prevent the cubes from clumping together. The rotation effectively transfers the momentum from the downward direction to the transverse direction, creating a lift-like lift that encourages the particles to float rather than fall to the ground.

Seyed-Ahmadi and Wachs conclude that cubic particles may be desirable for industrial applications that require improved mixing. And they say the model is a good substitute for other angled grains, such as. B. the particles that are formed in soil, rock and mining processes, which are typically polyhedral in shape.

–Rachel Berkowitz

Rachel Berkowitz is Corresponding Editor for physics based in Vancouver, Canada.


  1. A. Seyed-Ahmadi and A. Wachs, “Sedimentation of inert monodisperse suspensions of cubes and spheres”, Phys. Rev. Fluids6th044306 (2021).

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