Seed slippage: Champati cha-cha

(Press-News.org) WASHINGTON, Nov 19, 2024 – Champatis, the seeds of the Lapsi tree, are valued in Nepal for their medical, economic, social, and cultural significance. They are also popular among children as simple playthings. But for a group of physicists, these unique seeds—and the way they bounce and roll down slopes—could help them better understand landslides and avalanches, leading to research that could save lives.

In a study published this week in Physics of Fluids, by AIP Publishing, a team at the Technical University of Munich, the Kathmandu Institute of Complex Flows, and Tribhuvan University studied how Champatis roll and bounce down inclines. They suggested these seeds could serve as an analogue in the study of geological flow, particularly in a region prone to landslides and avalanches.

The Champati has a very complex structure. The wide head and narrow oval tail create a slope for each grain, leading to spin and rolling motion when sliding down slopes. This creates interesting dynamics that drew the attention of the research team.

“We are primarily interested in the scientific question of the dynamics and deposition of Champati slide: how it flows, where it goes, how far, and with what force,” said author Shiva Pudasaini from Kathmandu.

The authors released a heap of the seeds down an inclined plane while a camera recorded their descent to analyze their speed and the dynamics of their movement. The unique physical and geometrical properties of the supergrain led to previously unobserved dynamics as they slid down slopes. The team’s findings showed a unique property: The grains start to spread out slowly, then decrease quickly as they move downstream, akin to rock avalanches.

“Soon after the mass hits the ground, the behavior is unprecedented and appears to be highly unpredictable,” Pudasaini said.

This research may provide valuable insights into geological flows, including hyperspreading of rock avalanches, and could contribute to resolving challenges in this area. Additionally, findings may have significant implications for industrial process engineering.

Currently, the advanced mechanical, geotechnical, and imaging technologies needed for further study of the Champati seeds are not fully available in Kathmandu. To address this, the research team is expanding their measurement facilities and collaborating with well-equipped research institutions abroad.

However, while the initial results offer promising insights into fragmented rock avalanches, further investigation into the structural, mechanical, and dynamic properties of these grains is essential to fully understand their relevance to earth science and engineering.

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The article “The Champati slide” is authored by Shiva P. Pudasaini, Bekha R. Dangol, Chet N. Tiwari, Jeevan Kafle, Puskar R. Pokhrel, and Parameshwari Kattel. It will appear in Physics of Fluids on Nov. 19, 2024 (DOI: 10.1063/5.0230878). After that date, it can be accessed at https://doi.org/10.1063/5.0230878.

ABOUT THE JOURNAL

Physics of Fluids is devoted to the publication of original theoretical, computational, and experimental contributions to the dynamics of gases, liquids, and complex fluids. See https://pubs.aip.org/aip/pof.

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