‘Photoelastic discs are rolled down a narrow, inclined chute. The forces exerted when discs interact can be inferred from the intensity of the light they transmit. This information can be used to investigate how stresses are distributed within avalanches.’
An SPH simulation of the giant impact of a protoplanet twice the mass of Earth crashing into the young Uranus, thought to explain the planet's unique tilted spin, using an unprecedented 100,000,000 simulation particles – 1000 times more than the current standard – coloured by their thermal energy.
Two immiscible layers represent the stratified mid-latitude atmosphere, and internal interfacial waves develop and interact nonlinearly. A wide range of wave behaviours are observed: for example, the left-hand image shows two packets of spontaneously emitted inertia-gravity waves in the troughs of a large-scale baroclinic wave, while the right-hand image shows a rotationally modified Kelvin-Helmholtz wave generated from shear instability at sub-critical Richardson number. An optically active liquid generates different colours according to interface height.
Droplets of water (blue) and water-glycerol mixture (red) are propelled along the surface of a brass cone due to pressure gradients induced by the curvature gradient of the cone with larger droplets moving faster. The surface of the cone is lubricated with silicone oil allowing easy motion.
A column is formed in a rotating glass of water as fluorescent green dye is introduced. At low Rossby number, the Coriolis force dominates, controlling the dye motion. This unfiltered UV-illuminated image shows spiral filaments, mirroring the structure of a large-scale natural storm, also governed by the same invisible force.
This video relates our journey to look for order in the chaos of stratified turbulent flows. We tell the story of how we found three-dimensional coherent structures using cutting-edge experiments, and how we are just beginning to understand their origin using a modern stability analysis.
‘When a solid sphere hits an elastic sheet floating on the surface of water, wrinkles form and a capillary-like ripple propagates. The ripple propagates and the wrinkles grow with time — all due to an interplay between the elasticity of the sheet and the inertia of the fluid.’
This video shows formation of monodispersed multiple emulsion droplets with controllable number of inner droplets. Droplets are composed of exactly 4 water droplets enclosed within larger monomer drops. Both inner and outer droplets are highly monodispersed. Outer drops can be polymerised to preserve the structure.
'The images show the evolution of the structure of a shock-wave formed on a flexible aluminium plate as the supersonic flow interacts with the changing geometry of the deforming surface. Each pop art-inspired image is a composite of eight individual frames acquired using Schlieren photography in a supersonic wind tunnel.'
A millimeter-sized oil droplet can bounce on a vertically vibrated liquid bath for an unlimited time. It may couple to the surface wave it emits; leading to horizontal self-propulsion called walker. Its motion is captured optically with a Nikon camera whilst a LED light is illuminated through a diffuser (array of blue and yellow colour sheets).
Visualization of the trapping of finite Stokes number particles in a laminar flow. Three particles (in this case, LED capsules) encounter a flow instability in a chaotic flow region and eventually settle into a Kolmogorov-Arnold-Moser (KAM) tube where they move in helical orbits.
‘A fluid-driven fracture propagates radially in a transparent hydrogel. The fracture surface, post experiment, consists of beautiful fractal patterns called step-lines. These are small changes in height along the surface of the gel, which follow a logarithmic spiral shape.’
A millimeter-sized oil droplet can bounce on a vertically vibrated liquid bath for an unlimited time. It may couple to the surface wave it emits; leading to horizontal self-propulsion called walker. Its motion is recorded optically with a high-speed camera (Phantom MIRO110, 2000 FPS) and used a brown color backlighting. The presented video is 0.01x slower.
A three-dimensional direct numerical simulation of a heated chocolate fountain flow, including temperature and flow fields in a vertical slice. The geometrical structure is built from primitive geometrical objects using a state distance function (positive for fluid and negative for solid). Both the Navier-Stokes and thermal energy equations have been solved in the context of a front-tracking-based multiphase method and fluid structure interaction. Physical properties of melted chocolate (40°C) flowing and ambient atmosphere (20°C) have been used.
A vortex breakdown occurs as fluid flows from a rotating pipe into a stationary pipe at a constant rate. The decaying swirl creates an adverse pressure gradient on the pipe axis, which reverses the flow and forms a recirculation "bubble". The bubble's size is controlled by the speed of rotation.
A rotating rod is partially submerged in an aqueous solution (~1wt%) of polyacrylamide acid (PAA). With inertia present, a Newtonian fluid moves outwards toward the container walls. Here, however, the fluid climbs the rod due to the elastic stresses generated along the streamlines by the rotation of the rod.
'This video shows the transfer of mechanical energy and radiative pressure from Surface Acoustic Waves (SAWs) traveling along a solid surface into a droplet of water, dropped in the propagation path of SAWs, at 100k fps acquisition (slowed down 500 and 1500 times). The behaviour resembles an eruption and is used in medicine nebulisers.'
Fingering patterns form when air is injected into dyed glycerol in a Hele-Shaw cell with a soft upper boundary. As a result, the soft layer deforms. The change in the colour intensity of the dyed fluid reveals both global and local deformations of the soft layer.
‘Heat from lamps above the experiment is absorbed by dyed, salty fluid, heating it up and making it less dense. This warm fluid rises, but the heat diffuses away, leaving dense, salty fluid in narrow vertical plumes.’
(Left) A dandelion seed in a wind tunnel, with added clouds for effect. (Right) The same dandelion with the flow around it visualised using a laser sheet, showing the formation of a drag-enhancing vortex unlike any other observed before in nature, which we term a 'halo' vortex.
‘Composite binary images showing the spatio-temporal patterns formed when air displaces oil in a Hele-Shaw channel with an elastic upper boundary. By manipulating the initial level of collapse of the upper boundary, as well as the flow rate, we may observe a range of patterns, some reminiscent of feathers.’
As a liquid bath is perturbed, Faraday waves appear on the surface. Regular square patterns are observed for single-frequency forcing and the wavelength depends on the liquid properties and exciting frequency. The regular pattern becomes more complex by adding a second frequency component into the forcing signal.
This raw video shows wake pattern behind an oscillating cylinder. The forcing amplitude keeps constant; the frequency linearly ramps down. It is part of a systematic study where ramping up and down at various rates. Compared to the fixed frequency cases, ramping results in wake mode transition, skipping and hysteresis.
Formation of a “beads on the tail” of a viscoelastic droplet as it moves on an inclined superhydrophobic surface. The interaction of the surface features and the viscoelasticity of the drop results in a significant slowing of the drop – in comparison with an equivalent-viscosity Newtonian drop – and an instability on this fluid tail gives rise to the bead-like structure.
A computer-generated image of model sperm cells suspended in a Stokesian fluid, including the fluid velocity field. All sperm cells swim in the same plane and interact hydrodynamically, leading to visible cluster formation and locally enhanced flows.
'This is a high speed video showing jetting behaviour of a 20μL water droplet induced by ZnO surface acoustic waves (from left side). The jetting is induced by sub-nanometre amplitudes of surface acoustic waves interacting with water droplet, causing the droplet jetting along Rayleigh angle. However, due to a combination of acoustic pressure, internal flow, gravity force, surface tension and capillary, the droplet has been deformed significantly before fully jetted from substrates. '
‘"We should show life neither as it is, nor as it should be, but as we see it in our dreams" (The Seagull, by Anton Chekhov). Liquid crystal droplets in water, (accidentally) forming a pattern resembling a seagull's landing, viewed through a cross-polarising microscope.’
This image is a composite of five vorticity time series from simulations of stratified shear layers with increasing stratification. Each pixel column corresponds to a single time step from each simulation.
8 new recorded talks have been added recently.
Read MoreInitial information may be found at https://tinyurl.com/ukfc-2020-home Abstract submission will open in March 2020 and the closing date for submissions will be 17 April 2020.