Impact

The research programme investigates how fluid dynamics at the nano- and micro-scale can help the design and development of a wide range of future technologies and applications: from extracting drinking water from the sea to re-imagining aeroplane and ship hull surfaces for the best fuel efficiency.

The United Nations estimate that four billion people in 48 countries will lack sufficient water by 2050. As 97 percent of the water on the planet is saltwater, large-scale technologies to make seawater or other contaminated water drinkable are therefore needed urgently.

At the same time, figures from the US Energy Information Administration forecast that China's passenger transportation energy use per capita will triple over the next 20 years, and India's will double. Improving the fuel efficiency of air and marine transport is a strategic priority for governments and companies around the world, and would reduce the emissions that lead to climate change.

Over the next 40 years, engineering flow systems at the micro and nano scale will be a major part of the world’s response to the challenges that face us in transport, energy, climate and health. For example, recent research has indicated that membranes of carbon nanotubes are remarkably efficient at filtering salt ions from seawater. Also, it is possible that embedded micro systems or nano surfaces on aircraft surfaces and ship hull’s might drastically reduce drag, and thereby reduce emissions.

Many of the assumptions that underpin the conventional treatment of fluids are quite wrong when you consider very small systems. This research is about making sure we get the fluid dynamics right, and create reliable tools to help design future technologies.

 

Near-wall ‘streaks’ in the turbulent boundary layer: (left) plan-view experimental visualisation [4]; (right) linear numerical simulation — side (a), plan (b) and front-view (c) contour slices of streamwise velocity perturbation.

Aerodynamic drag reduction

The efficiency of modern transportation is severely compromised by the prevalence of turbulent drag. The high level of turbulent skin-friction occurring, e.g., on the surface of an aircraft or the carriage of a high-speed train, is responsible for excess fuel consumption and increased carbon emissions. The environmental, political, and economic pressure to improve fuel efficiency and reduce carbon emissions associated with transportation means that reducing turbulent skin-friction drag is a pressing engineering problem.

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Figure 2. Schematic of air trapped between hydrophobic microfeaturesof a super-hydrophobic surface. Reproduced from [8].

Super-hydrophobic nano-surfaces

Water repellency is important in many industrial and biological processes, including the prevention of the adhesion of snow to antennas and windows, self-cleaning traffic indicators, metal refinement, stain-resistant textiles, bioanalysisand cell motility. An application with major economic and environmental impact is drag reduction on marine vessels. According to a recent study for the International Maritime Organization, international shipping was responsible for annual emissions of around 843 million tonnes of CO2 in 2007, or around 3% of total man-made carbon emissions.

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Figure 4. Pilot MD simulation by the applicants of simple molecules flowing through an element of CNT membrane. A single CNT, anchored in substrates, is shown.

Water purification and desalination

The World Health Organization predicts that by 2050 up to four billion people (nearly two-thirds of the world’s present population) will face fresh water shortages. Drinking water scarcity is already posing major problems for more than a billion people, mostly in arid developing countries. As climate change continues to redistribute global rainfallpatterns such conditions will become increasingly common.

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