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
Prof. Duncan Lockerby, University of Warwick
It's a pleasure to welcome three new starters to Warwick and the Micro Nano Flows team. Laura Cooper joins us as a post-doctoral researcher, and will be working on multi-phase flow in porous media with James Sprittles. Yixin Zhang and Jacqueline Misfud are in the first weeks of their PhDs. Yixin will be investigating nano film stability (with molecular dynamics) and Jacqui will be researching micro-bubble cavitation (with CFD) in partnership with Waters Limited. We wish all three the best of luck in their research!
Dr James Sprittles, University of Warwick
Dr Shiwani Singh has joined the Micro and Nano Flows team at Warwick, where she will be based in the Maths Institute. She will be looking into multiscale modelling of viscoelastic flows over the next couple of years.
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.
Martin Nikiforidis, PhD Student, University of Edinburgh
One of the interested facts about water is that it does not always freeze and 273.15 K, as it normally does. Actually pure water, water that has no impurities and free of nucleation sites, can stay in liquid form up to 224.8 K.
When the purer water is supercooled it is very easy to freeze it, because any iteraction with the water molecules in that state can result in the fomration of nuclation sites, that will instantly result in the freezing of the water.
This video is a simple and nice representation on how to supercool water and then freeze it instantly!
Yixin Zhang, PhD Student, University of Warwick
Helium, which turns into liquid at about 4.2 Kelvin, can be held in a container like a beaker due to gravity. But when it is cooled further to below approximately 2 Kelvin, it creeps up the surface of the beaker and leak. At this temperature, liquid helium is called as superfluid due to its odd properties. For example, the liquid's viscosity becomes nearly zero. Because of that, the fluid can flow very easily even as a result of the smallest pressure. On one hand, a thin liquid helium film will appear as the liquid wet the surface of the beaker. On the other hand, liquid helium has smaller dielectric permittivity than any other medium (except vapour), which results in a negative Hamaker constant and a repulsive van der Waals force across the film. This will act to thicken the film and make the liquid helium flow from the bottom of the beaker to its surface and thus leak.
Jacqueline Mifsud, PhD Student, University of Warwick
A spherical bubble becomes unstable when it is subject to forces such as gravity, or when it is in proximity of surfaces such as walls or free-surfaces. The presence of such surfaces alters the surrounding pressure field, causing the bubble to lose its original sphericity, fold on itself and collapse. As the bubble collapses, some interesting and noteworthy flow phenomena take place. The detailed high-speed visualisations in the following video reveal some of these complex dynamics for a bubble collapsing close to a free surface.
In this case, it is the proximity of the free surface that causes the violent collapse. Once the laser-generated bubble grows to its maximum size, the collapse stage starts as the bubble begins to lose its sphericity. The upper part of the bubble accelerates downwards and becomes pierced by a liquid microjet. The jet itself tends to be difficult to observe visually, but its location can be identified by the protrusion it leaves when pushing part of the bubbles gaseous contents downwards.
When the jet impacts on the opposite bubble wall, a set of shock waves are emitted. In this case, the jet is so wide that it touches the interface not at a single point but in a ring, thus making the shock wave emission mechanism even more complex. Following jet impact, the bubble is separated into two parts, as the vapour cavity swept along by the jet becomes detached from the main toroidal bubble. Upon collapse of the main bubble, a stronger second set of shock waves is emitted which is reflected by the free surface causing excitation of nearby small bubbles.
More details here: https://doi.org/10.1063/1.4931098