Duncan Dockar

PhD Student, University of Edinburgh

I graduated from the University of Edinburgh in 2016 with a 1st class Honours with Masters in Mechanical Engineering (MEng). I am now a PhD student at the University of Edinburgh, within the Multiscale Fluids unit in the School of Engineering. My research areas include: nanobubble formation, stability and migration in free suspension and on nanoscale surfaces. 

Musical Boiling

Boiling is an important feature in many engineering processes, such as in the steam cycle in many power plants. It is also a highly multiscale phenomenon, with boiling bubbles nucleating on nanoscale features of solid substrates and growing to sizes of the order of mm. Researchers at Massachusetts Institute of Technology (MIT) have demonstrated the drastic effects that alterations at the nanoscale can have on boiling nucleation with the use of surfactants. By applying a voltage to certain parts of a substrate, the surfactants effectively render the substrate hydrophobic and can rapidly induce boiling at very specific regions of the substrate.

The rate at which boiling can be switched on or off is also particularly impressive, although as we all know the ultimate test for how fast scientists can control a process is by syncing it up with classical music… MIT calls this piece “Ode to Bubbles”, enjoy!

Cho, H. J. et al. Turning bubbles on and off during boiling using charged surfactants. Nat. Commun. 6:8599 doi: 10.1038/ncomms9599 (2015)

Happy New Year! Now how to deal with the snow?

Happy New Year, all! While the Hogmanay hangovers are beginning to wear off, we approach that time of year when the news headlines are dominated with “disruption”, “travel chaos”, and “winter storms”. I personally love snow, but when it comes to freezing temperatures and delays I definitely understand why some people don’t.

Airport staff possibly have the greatest reason to dislike snow. Aside from general runway clearing, deicing airplanes is an expensive, time-consuming, yet very necessary task. Ice accumulation on the wings of an aircraft increases weight which reduces fuel efficiency, but crucially also adversely affects airflow over the plane resulting in poor lift. Current deicing approaches are to spray airplanes with a heated glycol/water mix to melt existing ice and snow (glycol decreases the freezing temperature of water). A second step is also sometimes to spray the aircraft with a thicker, more concentrated glycol/water mix which prevents further ice forming on the aircraft body. This secondary deicing liquid slides off the plane during take-off so needs to be reapplied for every flight.

Part of our research at Micro & Nano Flows for Engineering is to investigate the onset of ice formation and how we can engineer materials which prevent the formation of ice on their surfaces, with the aim of eliminating the need for manual deicing processes. Applications for these technologies extend to almost all modes of transportation, such as railways, ships and roadways.

Lastly, in defence of winter I offer a photo of Edinburgh in the snow taken from Arthur’s seat during the holidays, as if you needed any more motivation to join us!

Ultrasonic dryers could shake your clothes dry

Researchers at the Oak Ridge National Laboratory, USA, have developed a clothes dryer that uses ultrasound transducers to dry water from clothes. Conventional dryers simply heat the wet clothes to evaporate water, a method which has largely been unchanged for decades. The prototype ultrasound dryers can dry laundry in around half the time of the conventional dryers, with an estimated 70% increased efficiency. The ultrasound method has also been found to reduce the risk of clothes shrinkage, colour fade and lint build up.

The technology has obvious implications for our own research here at the Micro and Nano Flows for Engineering group, where the unique fluid behaviour at decreasing length scales could lead to novel and often unintuitive engineering solutions.

Read more here

Water desalination using a graphene-oxide membrane

Scientists from the University of Manchester have successfully developed a graphene-oxide, laminate membrane capable of removing up to 97% of NaCl ions from salt-water. Their findings, published in Nature Nanotechnology, demonstrate a method for modifying the interlayer spacing between graphene-oxide sheets for “tunable ion sieving”.

Their research also corresponds well with our own work at the Micro & Nano Flows for Engineering Group. Dr Matthew Borg and Professor Jason Reese have recently published an article in the MRS Bulletin of an overview of their work in multiscale modelling of water transport through high aspect-ratio carbon nanotubes. Both articles highlight some important applications of micro and nanoscale fluid research, namely providing fresh drinking water for water-scarce areas of the world.

Read more here.

For astronauts needing that extra Buzz

A unique application of capillary flow allows workers aboard the International Space Station (ISS) to sip their coffee as easily as they would back on Earth. Designed by NASA astronaut Don Pettit, the cup makes use of a narrow, angled channel to draw liquid up by capillary action. This wetting effect is also unhampered by gravity on the ISS, allowing for a satisfying and uninterrupted drink.

 

Although it seems like just a bit of fun, the technology is already in use for fluid transport in weightless environments, such as in fuel tanks for rockets, micro-gravity condensing heat exchangers and multiphase fluid control. The unique behaviour of fluids in microgravity is especially relevant to our own research at the Micro & Nano Flows group and hopefully in time we will see many more interesting devices driven by unconventional fluid effects.

 

For those interested, a replica cup is available if you wish to drink like an astronaut, although with the addition of a stable, flat base for when gravity gets you down.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Read more here

View all blog entries