This Flow Webinar inaugurates the launch of Flow, a new, open-access, peer-reviewed journal designed to promote and exemplify the leveraging of the principles of fluid mechanics to concrete applications. Flow is published by Cambridge University Press and is a sister publication to the Journal of Fluid Mechanics. Flow defines applications broadly and encompasses technology that benefits humankind and also insights that offer a greater understanding of nature.
To celebrate this launch, this Flow Webinar features short talks which highlight the manifold impact of fluid mechanics across widely different fields. Talks will range from turbulent aerodynamics to systems for microfluidic assays, and from astrophysics and Earth’s climate to the life of microscopic creatures.
The Flow webinar took place on May 26th, 2021 at 4.00-6.35pm (BST). Video recordings of the talks are available below.
Programme:
4.00pm – 4.12pm Welcome remarks by Juan Santiago, Flow Editor in Chief (cambridge.org/flowwebinar/santiago)
4.13pm – 4.35pm Matthew England, UNSW, Australia
4.36pm – 4.58pm Mimi Koehl, UC Berkeley, USA
4.59pm – 5.21pm Mark Miesch, UCAR, USA
5.22pm – 5.44pm Lydia Bourouiba, MIT, USA
5.45pm – 6.07pm Parviz Moin, Stanford, USA
6.08pm – 6.30pm Charles Baroud, Ecole Polytechnique, France
6.31pm – 6.35pm Closing remarks by Juan Santiago
Welcome and introductions by Professor Juan Santiago, Flow Editor in Chief
Speaker: Matthew England, University of New South Wales
Title: Global ocean-atmosphere climate teleconnections
Video: cambridge.org/flowwebinar/england
Abstract: Interannual to multi-decadal climate variability across the global ocean-atmosphere system shows evidence of being interconnected across ocean basins and across hemispheres. In this talk, I will outline how global ocean-atmosphere climate teleconnections link the tropics to high-latitudes, and the Southern Ocean to the North Atlantic. Each of the tropical Pacific, Atlantic and Indian Oceans interacts with adjacent ocean basins as well as teleconnecting to polar latitudes. Via propagating planetary waves in the ocean, the Southern Hemisphere can trigger changes in the North Atlantic on multi-year time-scales, and in turn, the North Atlantic overturning circulation can alter the location of the ITCZ, the strength of the Walker Circulation, and the atmospheric circulation in the Amundsen Sea.
Speaker: Mimi Koehl, University of California, Berkeley
Title: Locomoting in a turbulent environment: Ways to study microscale processes in a large-scale ocean
Video: cambridge.org/flowwebinar/koehl
Abstract: Fluid mechanics is an important tool for understanding the biology and ecology of marine life. A major challenge in studying how microscopic aquatic organisms function in their natural habitats is integrating the different scales at which critical physical and biological processes occur. How can we make large-scale field measurements and models that include the behaviors and physical features of real organisms? Conversely, how can we design small-scale experiments to measure those biological factors under hydrodynamic conditions that reflect what the organisms actually experience in the largescale ocean? I will discuss examples of some of the approaches we have used to span different scales in our studies of how the interaction between the locomotion of microscopic organisms and the turbulent, wave-driven water flow around them determines how they move through the environment. We studied how the microscopic larvae of bottom-dwelling marine animals navigate to suitable habitats on the sea floor by combining field flow measurements in marine environments with flume studies, experiments in fluidic devices, experiments with dynamically-scaled physical models, and agent-based models of different locomotory strategies in measured turbulent flow fields.
Speaker: Mark Miesch, University Corporation for Atmospheric Research
Title: The Enduring Enigma of the Solar Cycle
Video: cambridge.org/flowwebinar/miesch
Abstract: Sunspots come and go every 11 years. To put it more precisely, the area of the solar surface covered by sunspots rises and falls with a quasi-regular 11-year cycle that is part of a more fundamental, and more extensive, 22-year magnetic activity cycle. We have known about this cycle for over 150 years and evidence from cosmogenic isotopes indicates that it has been occurring for thousands of years before that, at least. Some cycles are stronger than others, but it is not the variability of the cycle that is most puzzling. This is to be expected from a nonlinear dynamical system as complex as the solar interior. The puzzle is the regularity. Magnetic energy is generated from the kinetic energy of fluid motions through hydromagnetic dynamo action. So, elucidating the origins of cyclic solar magnetism is fundamentally an application of fluid dynamics. It is an epic saga that involves highly turbulent thermal convection shaped by rotation, stratification, and magnetism; persistent shear and global circulations maintained by the turbulent Reynolds stress and baroclinic torques; hydromagnetic instabilities, internal waves, and turbulent transport; subtle connections between large and small scales through turbulent cascades and the topological constraints of magnetic helicity. And, despite intensive theoretical, computational, and observational work dating back to the nineteenth century, it is still a mystery. Plausible explanations for the solar cycle have been proposed, but ongoing solar and stellar observations have not yet been able to resolve conflicting narratives. This talk will be a quick, whirlwind tour of the state of the art.
Speaker: Lydia Bourouiba, The Fluid Dynamics of Disease Transmission Laboratory, MIT
Title: Fluid dynamics and respiratory diseases
This was a live talk only, with no video recording available.
Abstract: The fundamental mechanisms governing respiratory pathogen spread between hosts and their persistence in the environment remain poorly understood with fundamental interdisciplinary challenges to be overcome. Fluid processes at various scales combined with biological processes are key in filling this gap. I will discuss how fluids and fluid dynamics at various scales contribute in shaping respiratory pathogen transport and fate and how interaction with other disciplines is key in formulating the key questions and advancing our knowledge of such systems.
Speaker: Parviz Moin, Stanford
Title: Progress in computation of turbulent flows-a new milestone in CFD
Video: cambridge.org/flowwebinar/moin
Abstract: Over the past decade there has been considerable progress in high fidelity simulation of multi-physics turbulent flows at reduced computational cost. This has been realized owing to improvements in computer power, advances in numerical methods and the associated algorithms, scalable mesh generation, and reduced order models to account for unresolved motions. A review of modern large eddy simulation technique (LES) for computation of complex turbulent flows will be presented. I will emphasize the critical importance of numerical methods used for LES. Methods with low numerical dissipation are essential for credible LES computations. In the absence of numerical dissipation, non-linear numerical stability and robustness is achieved by enforcing higher order discrete conservation principles.
Recent demonstration of the performance of wall modeled LES on grids of modest size in simulation of realistic aircraft has garnered considerable interest in aerospace industry. Predictions of quantities of engineering interest, such as lift, drag and pitching moment are in good agreement with experimental data at various angles of attack, including at maximum lift. The reported accuracy of the results and the affordable computational cost of the simulations, including that of grid generation, suggest that wall modeled large eddy simulation when used with non-dissipative numerical schemes and turbulent eddy resolving grids is on the threshold of readiness for industrial use in external aerodynamics.
Speaker: Charles Baroud, Ecole Polytechnique
Title: From the dynamics of microfluidic droplets to the dynamics of immune cells
Video: cambridge.org/flowwebinar/baroud
Abstract: Microfluidics has proven to be a key technology to produce and manipulate droplets, over a wide range of volumes, and with many applications in life sciences. In this context the focus in the early days of microfluidics was to understand the fluid mechanics that underlies the different droplet operations. I will start by discussing how droplet confinement can be used to generate and guide drops, particularly when gradients of confinement are generated by the microchannel geometry. Then I will switch to showing how we use these droplet operations to create 3D cultures of mammalian cells and how the combination of microfluidics with quantitative image analysis allows us to address a wide range of biological problems.
Enjoy free access to papers in support of Baroud's talk, courtesy of the Journal of Fluid Mechanics.