Solving the mysteries of granular materials flow

Monday, 23 November, 2015 | Supplied by: AXT Pty Ltd


Professor Itai Einav runs the Sydney Centre in Geomechanics and Mining Materials (SciGEM) at the University of Sydney — a research facility specialising in geomechanics and granular physics. This involves the study of the motion of granular materials such as soil and rock and their interaction with obstacles — an area of technology which is highly relevant to geotechnical engineering and ensuring the stability of buildings and other structures.

In their laboratories, Professor Einav and his researchers use experimental, theoretical and computer program models to predict how granular materials behave under various conditions. Their work has relevance to areas such as silo flow, conveying of grains and powders, hang-up delays in block cave mining, mixing and segregation in tumbling mills and rotating drums, and segregation of drugs in pharmaceutical powder compactions.

To test their theoretical models, the team has built a range of test rigs to demonstrate different flow and movement scenarios. These set-ups allow them to test and model scenarios such as inclines, conveyors, silos, etc. They have even constructed what is said to be the world's first facility for microanalysis of granular flow.

But while the team has been able to translate certain methodologies across from previous experiments, they needed to move away from reflected light to give a deeper understanding of how materials flow under given conditions. The logical choice was to use X-rays, which can provide a detailed 2D picture of what is going on. Professor Einav called on the expertise of AXT, a company with a long history in X-ray equipment and technologies. Together, they designed a custom solution incorporating X-ray source, high-voltage power supply, digital flat panel detector and other ancillary items sourced from AXT's suppliers.

The hardware supplied by AXT has been seamlessly integrated with software and models developed by Professor Einav's researchers, who can monitor fast-flowing dry granular materials. The system is said to work so well that they have decided to look at larger, more complex systems. This requires an extension to the existing set-up, with an identical system to be configured orthogonally to the original one. This will allow them to capture detailed 3D images so they can more accurately model real-life systems, giving their research more applied applications and relevance. This new capability will give Professor Einav's team the ability to track individual particle motions within larger bodies of flowing particles.

Silo discharge of 1 mm glass beads seen using X-rays, shown in real time.

“The addition of this extended capability is fully expected to give us new insights to help us prove or debunk many of the theories that have been postulated relating to materials flow," Professor Einav said. “As a result, we expect to make significant advances in the areas such as turbulence and segregation in granular flows, interactions between particles and flexible intruders in soils and the motion of fluids in porous networks."

Image caption: Dr Benjy Marks, Dr François Guillard and Professor Itai Einav studying granular flow using custom X-ray equipment.

Online: www.axt.com.au
Phone: 02 9450 1359
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