Micro & Nano Flows for Engineering
The micro & nano flows group is a research partnership between the Universities of Warwick and Edinburgh, and Daresbury Laboratory. We investigate gas and liquid flows at the micro and nano scale (where conventional analysis and classical fluid dynamics cannot be applied) using a range of simulation techniques: molecular dynamics, extended hydrodynamics, stochastic modelling, and hybrid multiscaling. Our aim is to predict and understand these flows by developing methods that combine modelling accuracy with computational efficiency.
Targeted applications all depend on the behaviour of interfaces that divide phases, and include: radical cancer treatments that exploit nano-bubble cavitation; the cooling of high-power electronics through evaporative nano-menisci; nanowire membranes for separating oil and water, e.g. for oil spills; and smart nano-structured surfaces for drag reduction and anti-fouling, with applications to low-emissions aerospace, automotive and marine transport.
EPSRC Programme Grant in Nano-Engineered Flow Technologies
Our work is supported by a number of funding sources (see below), including a 5-year EPSRC Programme Grant (2016-2020). This Programme aims to underpin future UK innovation in nano-structured and smart interfaces by delivering a simulation-for-design capability for nano-engineered flow technologies, as well as a better scientific understanding of the critical interfacial fluid dynamics.
We will produce software that a) resolves interfaces down to the molecular scale, and b) spans the scales relevant to the engineering application. As accurate molecular/particle methods are computationally unfeasible at engineering scales, and efficient but conventional fluids models do not capture the important molecular physics, this is a formidable multiscale problem in both time and space. The software we develop will have embedded intelligence that decides dynamically on the correct simulation tools needed at each interface location, for every phase combination, and matches these tools to appropriate computational platforms for maximum efficiency.
This work is strongly supported by nine external partners (see below).
- “Nano-Engineered Flow Technologies: Simulation for Design across Scale and Phase” EPSRC Programme Grant EP/N016602/1 01/16-12/20 (£3.4M)
- “The First Open-Source Software for Non-Continuum Flows in Engineering” EPSRC grants: EP/K038427/1 K038621/1 K038664/1 07/13-06/17 (£0.9M)
- “Multiscale Simulation of Interfacial Dynamics for Breakthrough Nano/Micro-Flow Engineering Applications” ARCHER Leadership Project 11/15-10/17 (£60k in supercomputer computational resource)
- “Skating on Thin Nanofilms: How Liquid Drops Impact Solids” Leverhulme Research Project Grant 08/16-08/19 (£146k funding a 3-year PDRA)
- Airbus Group Ltd
- Bell Labs
- European Space Agency
- Jaguar Land Rover
- Oxford Biomedical Engineering (BUBBL)
- TotalSim Ltd
- Waters Corporation
Latest news and blogs
Dr James Sprittles, University of Warwick
Warwick welcomes Vinay Gupta who has started a 2-year Commonwealth Rutherford Fellowship in the Mathematics Institute. Vinay's background is in exploiting moment methods to describe gas mixtures and granular gases.
Prof. David R Emerson, Daresbury Laboratory
Arnau Miro from the Universitat Politècnica de Catalunya won a HPC Europa-2 grant for a 13-week visit to the Daresbury group. Arnau will be working on advanced meshing and code coupling strategies and starts his visit mid-January.
Prof. Duncan Lockerby, University of Warwick
Following an international competition, Jason Reese has been awarded a prestigious Chair in Emerging Technologies by the Royal Academy of Engineering (RAEng).
These Chairs “identify global research visionaries and provide them with long-term support to lead on developing emerging technology areas with high potential to deliver economic and social benefit to the UK”.
For 10 years from March 2018, Prof Reese will be funded by the RAEng within the Micro & Nano Flows partnership to develop a new platform technology in multi-scale simulation-driven design for industrial innovation and scientific endeavour.
Yixin Zhang, PhD Student, University of Warwick
This fascinating video is from a paper titled "Nanowire liquid pumps" published in Nature Nanotechonology. It demonstrated that the outer surface of a nanowire is able to transport liquid. When liquid flows on the surface, it can flow as the thin film flows or the discrete beads. The former flow can be described by the well-known thin film instability while the latter is due to Rayleigh-Plateau Instability. In the thin-film instability, a minimum thickness of the thin film is achieved due to the repulsive intermolecular forces, which prevents the breakup of the thin film. This paper also shows that there is a critical film thickness of ∼10 nm separating two flow mechanisms.
Jacqueline Mifsud, PhD Student, University of Warwick
Although several mesmerizing videos of freezing soap bubbles out in the snow are available on YouTube, this phenomenon lacked scientific explanation. The following video explores some of the physics involved in freezing bubbles.
Researchers from Virginia Tech in Blacksburg investigated this phenomenon by depositing bubbles on a silicon substrate having temperatures between -10 and -40 degrees Celsius, with the surrounding air at room temperature. It was observed that the freeze front moves very slowly up the bubble, and in some cases even comes to a complete stop after reaching a critical height. The slow propagation of the freezing front is a result of the poor thermal conductivity of the thin soap film. The speed of propagation of the freeze front can be more readily observed in larger bubbles or at higher surface temperatures.
This delayed freezing consequently allows enough time for the frozen portion of the bubble surface to cool the air within the bubble, while the top part is still liquid. As a result, a pressure imbalance is developed that either collapses the top or causes the top to pop. When the freeze front manages to reach the top of the bubble, a section of the top may melt and slowly refreeze. This melting and refreezing cycle can take place several times in a single bubble.
The last part of the video shows freezing bubbles in a freezer, where the surrounding air was maintained at -20 degrees Celsius. Under these conditions, the bubble freezes quickly and the ice grows radially from nucleation sites rather than perpendicular to the surface. This contrasts with the limited conductivity of bubbles deposited on a cold surface in room temperature.
Differences in surface tension (or Marangoni effects) create currents in soapy films that move ice crystals around. The result is a variety of ice crystals swirling across the surface of a soap bubble as it freezes, making it look somewhat similar to a snow globe.
Dr Rohit Pillai, Research Associate, University of EdinburghJason, Matthew and I have had an article published in Physical Review Letters detailing our research in vibration-induced heating of water nanofilms. We were asked to provide a 200 word summary of the article, written in a manner accessible to the layperson. I found this to be a valuable exercise, as the required style of writing is completely different from that expected in a paper. I thought I'd post our final version here, as it may provide some value to future researchers within the group and elsewhere. For those interested, the actual paper is available at: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.104502Shaken, not sprayed: A new way of heating liquids using vibrationsIf you vigorously shake a water droplet resting on a flat surface it can break up into a fine mist, similar to the liquid sprays from aerosol cans. However, we have shown, for the first time, that intense vibrations can also be used to boil water and other liquids. Using molecular simulations, we have demonstrated this effect in extremely thin liquid layers - some thousand times thinner than a human hair - resting on a vibrating surface. The vibrations also have to be very high frequency, around a million times quicker than the flapping of a hummingbird’s wings. Under these conditions the thin film of water boils, just due to the shaking – imagine a tiny vibrating kettle! This discovery could stimulate ideas for new nanotechnologies: vibrating nano-arrays may be able to prevent ice formation on airplane wings, cool the electronic circuits in our smartphones and laptops, and dry clothes quicker for lower electric bills. Thus, exploiting this new science of vibrations at the smallest scales could, literally, ‘shake things up’ in our everyday lives.