School research reveals secrets of nanobubbles

Bubbles coming off a ship's propeller when they have reached larger sizes (left), and the damage caused when these bubbles collapse on another propeller (right)
Bubbles coming off a ship's propeller when they have reached larger sizes (left), and the damage caused when these bubbles collapse on another propeller (right)
School of Engineering researchers have revealed insights into how minute, yet powerful, bubbles form and collapse on underwater surfaces. This new understanding could help make industrial structures such as ship propellers more hardwearing.

Supercomputer simulations

Researchers from the School’s Institute for Multiscale Thermofluids, the late Regius Professor of Engineering Jason Reese, Dr Matthew Borg, and postgraduate research Duncan Dockar, modelled complex simulations of air bubbles in water, using the UK’s national supercomputer.

These simulations revealed details of the growth of so-called nanobubbles, which are tens of thousands of times smaller than a pin head.

The team modelled the motion of atoms in the bubbles and observed how they grew in response to small drops in water pressure. They were able to determine the critical pressure needed for bubble growth to become unstable, and found that this was much lower than suggested by theory.

This rapid expansion and collapse of bubbles, known as cavitation, is a common problem in engineering but is not well understood.

Potential applications

The findings could lend valuable insight into damage caused on industrial structures, such as pump components, when these bubbles burst to release tiny but powerful jets of liquid.

The discovery could also inform the development of nanotechnologies to harness the power of thousands of jets from collapsing nanobubbles, such as therapies to target some cancers, or for cleaning high-precision technical equipment.

Researchers have proposed an updated theory on the stability of surface nanobubbles, based on their findings.

Duncan Dockar commented: “Bubbles routinely form and burst on surfaces that move through fluids and the resulting wear can cause drag and critical damage. We hope our insights, made possible with complex computing, can help limit the impact on machine performance and enable future technologies.”

Their study, published in Langmuir, was supported by the Engineering and Physical Sciences Research Council.

Source: University of Edinburgh news

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