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 Juan C. Padrino, Research Fellow, University of Warwick
MNF will be present in the upcoming 3rd UK InterPore Conference on Porous Media to be held at the University of Warwick, Coventry, UK, on 4 and 5 September 2017. On the afternoon session of 5 September, Juan C. Padrino will give a talk on multiscale modeling of diffusive transport in complex networks.
Dr Benzi John, Senior Computational Scientist, Daresbury Laboratory
Benzi John (PI) and David Emerson (Co-I) have successfully won about 32, 000 KAU (~ £18,000) frunding from EPSRC to run large-scale simulations on ARCHER. The project titled "High fidelity non-equilibrium DSMC flow simulations at scale using SPARTA" will run for 12 months, starting from August 1st 2017. More information here.
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!
Chengxi Zhao, PhD Student, University of Warwick
It is widely acknowledged that the flight principle of biological flapping wings (birds, bats and insects) is different from the one of the fixed wings (flight vehicles). For a cruising aeroplane, gases around the wings can be simplified to the steady flow. Lifts come from pressure differences caused by airfoil shapes. However, unsteady characteristics can never be neglected when studying the flapping wings. The flapping motions usually generate vortexes over the upper surfaces of wings. Moreover, the flexibility of biological material makes the problem more difficult because fluid-structure interaction also has to be taken into consideration.
The video above shows that honey bees flap their wings up to 250 times a second. It is quite amazing for their small short wings to get the 'fat' body off the ground.
An interesting idea is that such low Reynolds number flow may exhibit rarefied phenomena at very small scales. Some researchers found that low Reynolds number flows are viscous and compressible, and rarefied effects increase when the Reynolds number decreases (Sun Q. and Boyd I.D., 2004). They also concluded that a flat plate having a thickness ratio of 5% has better aerodynamic performance than conventional streamlined airfoils in rarefied gases. However, it seems that few studies of the topic were carried out after the paper. In my opinion, it is interesting and important to study the rarefied gas effects around the flapping wings to get a deeper understanding of the flight principles of small insects.
Dr Juan C. Padrino, Research Fellow, University of Warwick
Recently, from the 19th to the 21st November of 2017, I was part of a group of researchers from the University of Warwick that attended the 70th annual meeting of the Division of Fluid Dynamics (DFD) of the American Physical Society (APS) in Denver, Colorado, USA. This is a well-established international meeting with a large turnout. Besides having invited talks, posters, and the well-regarded Gallery of Fluid Motion with videos, the main body of the conference consists of usually more than thirty-five parallel sessions in all topics related to fluid mechanics, from theoretical aspects and mathematical foundations to experimental techniques, passing through high-performance computational fluid dynamics, and from nano- and micro-fluidics to flow in the Earth’s atmosphere, oceans, and even in the outer space.
Mykyta Chubynsky giving his talk at the 2017 APS DFD.
Because I attended many talks in those three days and it would be impractical to refer to each of them, I will briefly summarize here just a few of them that I consider as highlights.They are all related with phenomena typical of the flow at the nano- and micro-meter scales.
First, in the third session on evaporation and heat transfer on drops, Takeru Yano discussed the solution of the Boltzmann equation in the half-space for the non-equilibrium gas flow having a planar interface undergoing evaporation or condensation. He studied the flow on the basis of the numerical solution of the Boltzmann–Krook–Welander (BKW) equation. In the journal “Fluid Dynamics Research”, this author presented an article that explains in detail part of his talk at the 2017 APS DFD meeting.
Secondly, within the focus session on “Modeling, Computations and Applications of Wetting/Dewetting Problems III”, Vladimir Ajaev talked about modeling the motion of contact lines over substrates with spatially-periodic non-uniform patterns. The mathematical analysis was carried out using the lubrication approximation, and including evaporation, capillary effects due to interfacial-tension variation with temperature, and disjoining pressure (DP). It is worth noting that the last factor was modeled as the superposition of the van der Waals DP and the electrostatic DP. These two-component DP model is recommended when dealing with fluids, such as aqueous solutions, where electrical charges, in the form of ions, are present in the body of the liquid. In the first part of this focus session, a member of our Micro- and Nano-Flows Group at Warwick, James Sprittles, presented his talk on kinetic effects in dynamic wetting.
In the session on instability, break-up and splashing of drops, a presentation that caught my attention was that co-authored by Riboux and Gordillo. In their talk, they extended previous work on modeling the fluid dynamics of the thin liquid sheet ejected after drop contact with a solid surface in the splashing process to include the effects of the boundary layer. They showed good agreement between theory and experiments. More details of their work can be found in this article.
Dave Emerson, from STFC Daresbury Laboratory, during his presentation at the 2017 APS DFD.
In the session on Modeling of Microscale Flows, Dave Emerson, another member of our group affiliated with STFC Daresbury Laboratory also in the UK, presented a talk discussing the challenges with modeling thermal flows in the slip-flow regime. He commented on recent results that suggest that using the Navier-Stokes-Fourier equations with modified boundary conditions to account for rarefaction effects for thermal problems in the slip flow regime can produce erroneous answers. Emerson presented alternative modeling approaches based on macroscale field variables capable of overcoming these limitations.
There were also several invited talks. For instance, Jen Eggers talked about the role of singularities in hydrodynamics and Detlef Lohse discussed the characteristics of turbulent flow arising from Rayleigh-Benard or Taylor-Couette instabilities. In particular, I would like to refer to the invited talk given by Sungyon Lee on two-phase flow in a Hele-Shaw cell. Flow in a Hele-Shaw refers to fluid motion in the narrow space between two wide parallel plates, with a gap in the order of a few millimeters or smaller. It is a useful and practical set-up that serves as a surrogate to study the inaccessible flow of one or more phases in porous media. In her talk, by means of videos of experiments conducted by her research team, she showed that a more viscous fluid displacing a less viscous one in a Hele-Shaw cell --- a stable configuration in the sense that an initially smooth interface remains smooth throughout its motion --- can lead to an unstable moving front when solid particles are injected and transported near the interface. More details can be found here.
Sungyon Lee talking about particle-induced instability when a more viscous fluid displaces a less viscous one at the 2017 APS DFD.
The participation of J.C. Padrino in the APS-DFD annual meeting of 2017 in Denver was possible thanks to a research fellowship funded in the United Kingdom by the Engineering and Physical Sciences Research Council (EP/N016602/1).
Dr Stephen M. Longshaw, Research Fellow, Daresbury Laboratory
Well, it's that time of year again, no not Christmas, conference time!
Recently members from the MNF group have been at a number of large conferences, with Prof. David Emerson attending both SuperComputing 2017 and then, with other members of the group, the APS conference in Denver in America.
I recently found myself at the UK's version of SuperComputing, the STFC run Computing Insight UK, although a smaller event than SuperComputing, this year still saw around 400 people come together in Manchester in the UK to see the latest computing technologies, discuss how to join up the UK's e-Infrastructure (i.e. how can we all get better access to the nations HPC resources) and, the reasons I was there, a day long session on emerging computing technology, which I ran! This was an exciting event for me as we didn't just have speakers, instead we also ran a 3 hour practical work-shop on hands-on Quantum Computing in collaboration with IBM Research. This went down fantastically and we hope to run something similar in the future.
The next exciting event is the annual MNF Christmas conference and workshop on the 18th and 19th of December! This is behing held over 2 days in Cheshire, with the first day being devoted to engaging with our industrial partners in a steering and impact committee day and the second for the group to come together and update each other one what we have all been doing! Events like this are essential with research groups as large as this one, we are spread over a number of institutions and not all working together so this event is a really great opportunity.
In the meantime, here are a few photos from the EMiT@CIUK 2017 workshop showing me looking awkward in front of a camera (watch the STFC media feeds for the full interview if you want something to laugh at) and Dr Stefan Filipp from IBM Research Zurich teaching us all about the state of quantum computing, how we can learn it now and what it can be applied to in the future. Fascinating stuff, especially for the future of molecular modelling!
Finally, if you want to have a play with quantum computing yourself, I enourage you to go to the IBM Quantum Experience website, where you can run on an actual quantum machine hosted in the IBM York Town research facility. More importantly though it offers a great set of tutorials to help you find out the important basics such as "what is a qubit?", "how do i teleport data between them", "who or what is a Hadamard gate?" and many others! Have a look here: https://quantumexperience.ng.bluemix.net/qx