The impact of water (Day 299)

The impact of water (Day 299)

22nd March 2015

This year, World Water Day focuses on the following ideas: water is health; water is nature; water is urbanisation; water is industry; water is energy; water is food; and water is equality. But I want to add something to this list: water is chemical engineering.

The importance of water is often overlooked. Water is not only essential for life but it is of key importance in chemical engineering too.

In the past, I have discussed the relationship between water and food, water and energy and the water-energy-food nexus, and I can’t stress enough the importance of these interdependencies.

Today, however, I thought I’d focus on the more light-hearted work of the chemical engineers at the University of Minnesota, US, who are working to understand the impact of raindrops.

This work led by Assistant Professor Xiang Cheng, but conducted by three undergraduate chemical engineering students: Runchen Zhao; Qianyun Zhang; and Hendro Tjugito, was recently published in PNAS under the title: Granular impact cratering by liquid drops: Understanding raindrop imprints through an analogy to asteroid strikes.

Xiang and his team were rewarded for their mesmerising work with a Gallery of Fluid Motion Award at the 67th American Physical Society Division of Fluid Dynamics meeting held in November 2014.

Their video was selected as one of three winners out of 75 submissions, judged not only on the videos’ scientific content but also its artistic value and originality. You can admire their work here:

This video shows the impact of water on a granular surface.  This is a phenomenon familiar to all of us who have watched rain falling on a beach - an all too common occurrence here in the UK. The impact of the water droplets creates impact craters with fascinating and scientifically important shapes.

When a granular material is impacted by a sphere, its surface deforms like a liquid, yet it preserves a circular crater like a solid.

Although the mechanism of granular impact cratering by solid spheres is well understood, our knowledge of granular impact cratering by liquid drops is still limited.

The team found that these craters follow the same energy scaling and reproduce the same crater morphology as those of asteroid impact craters on planetary bodies. Inspired by this similarity, Xiang’s group developed a simple model that quantitatively describes the observed crater morphologies.

This research shines a light on the mechanisms governing liquid droplet impacts on granular materials.  It also highlights the surprising discoveries that research can reveal and demonstrates the beauty of chemical engineering.

A fitting example of chemical engineering research on World Water Day.

Please get in touch and tell me why your work with water makes an impact.