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ASC seminar: Aerodynamics and Fluid-Structure Interaction of Small Flyers
Group: Autonomous Systems and Connectivity
Speaker: Dr. Chandan Bose, University of Edinburgh
Date: 10 March, 2023
Time: 14:00 - 15:00
Location: James Watt South Building, Room 603
Speaker Biography
Chandan completed his graduation in Civil Engineering from Jadavpur University, India, in 2013, where he was the university gold medalist (first class first) of his batch. He received his master’s and PhD degrees from the Department of Applied Mechanics at the Indian Institute of Technology Madras, India, in 2019. His PhD research was on the dynamical analysis of the unsteady flow phenomena around a flapping wing through high-fidelity numerical simulations and wind tunnel experiments. He received the Institute Research Award (IIT Madras), V. Ramamurthy Best Thesis Award (IIT Madras), and the prestigious Indian National Academy of Engineering Innovative Project Award for his doctoral research contribution. Following his PhD, he did a postdoctoral stint at the University of Liege, Belgium, where he was awarded the Wallonie Bruxelles International Excellence Postdoctoral Fellowship and FNRS Postdoctoral Fellowship to work on nonlinear aeroelasticity and fluid-structure Interaction. He has been chosen as one of the outstanding reviewers of the Year 2020 by the ASME Journal of Computational and Nonlinear Dynamics. He is presently working on the ERC CoG project “Dandidrone” as a senior postdoctoral research associate at the School of Engineering, The University of Edinburgh, to study the underlying fluid-structure interaction dynamics of dandelion seed propulsion and its application towards building a microdrone. He is also an adjunct lecturer at the School of Engineering, The University of Edinburgh and an incoming assistant professor of Aerospace Engineering at the University of Birmingham. He is a member of the OpenFOAM Technical Committee and part of the local organising committee of OpenFOAM Workshop 2021 (University of Cambridge, UK) and the upcoming OpenFOAM Workshop 2022 (University of Genoa, Italy).
Abstract
The present talk will focus on the wake dynamics and fluid-structure interactions involved in different flight mechanisms of small flyers in the low Reynolds number regime. The outline of the talk will be divided into two primary focus areas: flow dynamics of active and passive flight of small flyers. There are a variety of natural small flyers from the animal kingdom, like insects, who exploit their complex aerial acrobatics through active wing kinematics to generate sufficient aerodynamic forces to fly. On the other hand, there is another class of passive flyers from the plant kingdom, like dandelion seeds, which exhibit long-distance dispersal through a passive flight by extracting energy from the wind gusts and the updrafts. In the first case, the active flyers periodically use their flapping wings and exploit the wing flexibility to augment the aerodynamic efficiency. Although periodic flapping motions are usually expected to lead to periodic and organized wakes at low Reynolds numbers, our investigations have revealed a range of kinematic parameters, which gives rise to chaotic flow fields and in turn, unpredictable chaotic aerodynamic loads. We have established the route to chaotic transition in the flow past a flapping wing and unraveled the fundamental vortex interaction mechanisms responsible for manifesting chaos in the flow field. We have observed that even a small erratic behavior of the leading edge vortex could spell a complete eventual breakdown of a regular wake in the high Strouhal number regime. The presence of chaos is highly undesirable from the viewpoint of flapping flight control and presents a fundamental practical problem. To that end, we have discovered that the chordwise flexibility of the wings plays a pivotal role in regularizing the wake and inhibiting chaos. In the latter example of passive flyers, dandelion seeds exploit the wind gusts and updrafts in turbulent flows using a bundle of drag-enhancing bristles, called pappus. The highly porous filamentous pappus of the dandelion seed is simplistically modeled as a passively flying porous disc with a displaced center of mass to capture the essential dynamics from a macroscopic approach. Our study uncovers the role of porosity and permeability on the long dispersal of these biological seeds, such as dandelions, understanding the flight mechanisms deployed by nature to keep the dandelion seeds aloft. Furthermore, we systematically characterize the role played by the wind gusts and updrafts in enabling the long-distance wind dispersal of the dandelion seeds. The gust effect depends on the terminal velocity of the seed, which in turn is a function of Reynolds number, Darcy number, and the non-dimensional moment of inertia of the system. The fundamental wake-structure interactions in the vortex-dominated flow around the falling porous body provide us insight into the flight mechanism. An appropriate understanding of the flight mechanism of these small flyers and their gust response will directly benefit the design strategies of insect-scale drones and micro aerial vehicles. These futuristic devices are envisaged to have multi-fold applications in environmental monitoring in areas inaccessible to humans and in building distributed sensor network systems.
Innovative Wireless Powering, Sensing and Connectivity for Sustainable Flexible Electronics and Low-Carbon Internet of Things
Group: Autonomous Systems and Connectivity
Speaker: Dr. Chaoyun Song, Heriot Watt University
Date: 09 December, 2022
Time: 11:00 - 12:00
Location: James Watt South Building, Room 361
Abstract Flexible and stretchable electronics present a paradigm shift in bio-compatible and skin-attachable devices that enable radical applications in such as human-to-machine intelligence, Internet of Human Bodies (IoB), VR, AR and metaverse. An emerging update for traditional radio frequency (RF) technologies will be needed to accommodate antennas, circuits and sensors on highly flexible and unconventional substrates and systems. Consequently, new challenges will be presented for future electronic engineers, in terms of the antenna/circuit performance detuning and wavelength variations due to mechanical strain, bending and twisting. Moreover, in combination with the latest rectenna and wireless power transfer technologies, the most challenging and non-flexible parts – batteries will be effectively eliminated for future flexible and stretchable electronics, thereby showcasing a self-sustainable solution towards the Net Zero Target 2050. In this talk, the heritage achievements of the presenter’s research group on low-power wide spectrum wireless energy harvesting will be firstly introduced, then the system level integration between wireless powering, sensing and communication on state-of-the-art flexible materials will be highlighted. Some emerging applications and industrial activities to address the challenges in low-carbon IoT will be discussed. Finally, future research directions and the presenter’s vision of this field will be presented.
Bio: Chaoyun Song (IEEE Senior Member) received his BEng. MSc (with distinction) and PhD degrees all in electrical engineering and electronics from The University of Liverpool (UoL), Liverpool, UK, in 2012, 2013 and 2017, respectively. He is currently an Assistant Professor within the School of Engineering and Physical Sciences, Heriot-Watt University, UK.
He has authored/co-authored more than 90 papers (including 34 IEEE Transactions) in leading journals and conference proceedings. He has filed six US, EU, and UK patents. His current research interests include wireless energy harvesting and power transfer, rectifying antennas (rectennas), flexible and stretchable electronics, metamaterials and meta-surface, and low-power sensors.
Local host: Mahmoud Wagih - ASC
Beamforming techniques for multiple beam antenna systems in satellite and terrestrial communication networks
Group: Autonomous Systems and Connectivity
Speaker: Nelson Fonseca, European Space Agency
Date: 25 November, 2022
Time: 10:00 - 11:00
Location: https://uofglasgow.zoom.us/j/9036388808 Meeting ID: 903 638 8808 Passcode: 234567
Recent developments in both terrestrial and non-terrestrial networks are focused on multiple beam antenna systems as a mean to increase data rates and to provide more flexibility in resource allocation. Some synergies between space and terrestrial systems are emerging as the fifth generation (5G) of wireless systems introduce millimeter-wave frequencies for short range and indoor applications. This provides a unique opportunity for transfer of technology, as requirements for satcom user terminals and cell tower antennas present some similarities. While phased array antennas are getting a great deal of attention, their cost still remains high for mass market applications and alternative solutions based on simpler beamforming techniques are being considered. This talk will review well-known beamforming techniques, including Butler, Blass and Nolen matrices, and discuss their respective advantages and limitations. Recent developments, including a first demonstration of a planar array with a triangular lattice of beams, will also be presented. Microwave components, such as couplers and phase shifters, are key building blocks of beamforming networks. Recent developments with the University of Glasgow on the use of AI for the optimization of such components will also be presented.
Aerospace Research Seminar: Turbulent reacting flows with particle formation
Group: Autonomous Systems and Connectivity
Speaker: Dr. Stelios Rigopoulos, Imperial College London
Date: 06 March, 2020
Time: 15:00 - 16:00
Location: James Watt South Building, Room 361
Abstract:
Aerospace Research Seminar: Tidal power and turbulence - Unsteady hydrodynamics in 3D
Group: Autonomous Systems and Connectivity
Speaker: Dr. Amanda Smyth, Cambridge University
Date: 05 December, 2019
Time: 11:15 - 11:45
Location: Rankine Building, Room 816
Tidal power and turbulence: Unsteady hydrodynamics in 3D
Abstract:
Tidal power has huge potential as a source of predictable renewable energy in the UK, but the harsh operating environment increases the costs of manufacture and maintenance, and reduces the reliability of the resource. This talk will focus on the damage caused to turbines by surface waves and ocean turbulence, which often leads to overloading and premature failure of tidal devices.
A number of recent studies have shown that the low-order models used by industry to predict turbine load response to turbulence and waves are not capable of reproducing experimental results, even for very simple unsteady forcing. The cause of this discrepancy is that conventional low-order models are based on 2D strip-theory, which ignore any 3D effects on the unsteady hydrodynamics. 3D effects are in fact substantial in most tidal applications; the turbines themselves are highly 3D in shape (small aspect ratios and highly tapered), and the unsteady flow fields also have significant spatial variation. In this talk we will look at the impact of both of these 3D features on the unsteady loads experienced by tidal turbines.
Speaker Bio:
Amanda Smyth is a Research Associate at Cambridge University Engineering Department, working in the Whittle Laboratory. She studied for a MEng in Mechanical Engineering at Imperial College London, after which she did her PhD at Cambridge University on "Three-Dimensional Unsteady Hydrodynamics of Tidal Turbines". Her work explores the limitations of using two-dimensional strip-theory methods for calculating the unsteady hydrodynamic loading experienced by tidal turbines, which are highly three-dimensional in shape. She is also working on developing turbine blades that are resistant to unsteady and turbulent flow, in order to increase the longevity and reliability of tidal devices.
From Superhydrophobic to Super-Slippery Surfaces
Group: Autonomous Systems and Connectivity
Speaker: Professor Glen McHale, Northumbria University
Date: 09 March, 2018
Time: 14:00 - 15:00
Location: Rankine Building, Room 514
On a wet day we need coats to keep dry, windscreen wipers to see and reservoirs to collect water and keep us alive. Our cars need oil to lubricate their engines, our ships need hulls that reduce drag and our planes need wings that limit ice formation. Nature has learnt to control water in a myriad of ways. The Lotus leaf cleanses itself of dust when it rains, a beetle in the desert collects drinking water from an early morning fog and some spiders walk on water. In all of these effects the unifying scientific principle is the control of the wettability of materials, often through the use of micro- and nano-scale topography to enhance the effect of surface chemistry. In this seminar I will outline recent examples of our research on smart surface-fluid interactions, including drag reduction and flow due to surface texture,1-4 interface localized liquid dielectrophoresis to create superspreading and dewetting,5-7 lubricant infused surfaces to remove pinning,8-10 and the Leidenfrost effect using turbine-like surfaces to create new types of heat engines and microfluidics.11-12
References
1. Busse, A. et al. Change in drag, apparent slip and optimum air layer thickness for laminar flow over an idealised superhydrophobic surface. J. Fluid Mech. 727, 488–508 (2013).
2. Brennan, J. C. et al. Flexible conformable hydrophobized surfaces for turbulent flow drag reduction. Sci. Reports 5, 10267 (2015).
3. McHale, G. in Non-wettable Surfaces Theory, Prep. Appl. (Ras, R. & Marmur, A.) (RSC, 2016).
4. Li, J. et al., Topological liquid diode. Science Advances 3, eaao3530 (2017).
5. Brown, C.V. et al. Voltage-programmable liquid optical interface. Nat. Photonics 3, 403–405 (2009).
6. McHale, G. et al. Voltage-induced spreading and superspreading of liquids. Nat. Commun. 4, 1605 (2013).
7. Edwards, A.M.J. et al. Not spreading in reverse: The dewetting of a liquid film into a single droplet. Sci. Adv. 2, e1600183 (2016).
8. Ruiz-Gutiérrez, É. et al., Energy invariance in capillary systems. Phys. Rev. Lett. 118, art. 218003 (2017).
9. Guan, J.H. et al., Drop transport and positioning on lubricant-impregnated surfaces. Soft Matter 12, 3404-3410 (2017).
10. Luo, J.T. et al., Slippery liquid-infused porous surfaces and droplet transportation by surface acoustic waves. Phys. Rev. Appl. 7, 014017 (2017).
11. Wells, G. G. et al., A sublimation heat engine. Nat. Commun. 6, 6390 (2015).
12. Dodd, L.E. et al., Low friction droplet transportation on a substrate with a selective Leidenfrost effect. ACS Appl. Mater. Interf. 8 22658–22663 (2016).
Acknowledgements The financial support of the UK Engineering & Physical Sciences Research Council (EPSRC) and Reece Innovation ltd is gratefully acknowledged. Many collaborators at Durham, Edinburgh, Nottingham Trent and Northumbria Universities were instrumental in the work described.
Biography. Glen McHale is a theoretical and experimental applied and materials physicist. At Northumbria University, he combines leading the Smart Materials & Surfaces laboratory with his role as Pro Vice-Chancellor for the Faculty of Engineering & Environment. His research considers the interaction of liquids with surfaces and has a particular focus on the use of surface texture/structure via microfabrication and materials methods, and the use of electric fields to control the wetting properties of surfaces. His work includes novel superhydrophobic surfaces, surfaces with drag reducing and slippery properties, and electrowetting/dielectrophoresis to control the wetting of surfaces. Glen has written invited “News and Views”, highlight, emerging area and review articles for a wide range of journals covering superhydrophobicity, dynamic wetting, liquid marbles and drag reduction. He has published over 170 refereed journal papers. He is a Fellow of the Institute of Physics, a Fellow of the RSA, a Senior Member of the IEEE, a member of the UK Engineering & Physical Sciences Research Council (EPSRC) Peer Review College, and he was a panel member for the "Electrical and Electronic Engineering, Metallurgy and Materials" unit of the last UK-wide national assessment of research (REF2014). Along with colleagues at Northumbria, Nottingham Trent and Oxford Universities, he has developed a public understanding of science exhibition, "Natures Raincoats" (www.naturesraincoats.com).
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