Gallery

Symmetry breaking of sheets to vorticity filaments by a finite perturbation.

Hot suspension of temperature-sensitive phosphor particles was dripped into a cuvette half-filled with cold water. The cuvette was illuminate by a UV light sheet. The particles were cooling down due to the mixing process, and the emission spectrum shift from blue towards green. This emission property sheds light on a novel technique that can implement simultaneous temperature and velocity imaging in fluids. (Original photo; no enhancement.)

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. (Minor adjustments were made to brightness and contrast.)

The oblique splash of a 3.3 mm diameter water droplet on a thin flowing liquid film. The droplet's fall height is 0.25 m from the impact surface while the film is flowing at 3 L/min, on a glass substrate inclined 15 degrees to the horizontal. Image captured 7.2 ms after impact.

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. (The image was created using a cmocean colormap, and was further edited for saturation and contrast using RawTherapee.)

The image shows the flow topology for a flat plate wing rotated 180 degrees about the mid chord. The experiment was conducted in a quiescent water tank, and the shear layer feeding vortices behind each plate edge is illuminated using a milk based dye and twin laser light sheets.

This is a picture from a high speed video showing jetting behaviour of a 20uL 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. (The photo is not a composite and has not been enhanced.)

Jet noise is the dominant source when the aircraft takes off. It can be even higher when the engine is installed closed to the wing. The additional noise can be caused by nonlinear hydrodynamic jet-wing interactions and linear TE acoustics scatterings. Large-eddy simulation is performed to understand noise sources, and noise reduction technology is explored using serrated nozzles.

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.

Slice from a 3D two-way coupled DNS homogeneous isotropic turbulent flow containing 20 million solid particles. The background represents the Okubo-Weiss parameter, with particles avoiding red zones (vorticity overwhelms strain) and concentrating in the blue regions (the opposite). Taylor Reynolds is 35.4, Stokes 0.4 and mass loading 0.5.

This video shows sediment being fluidised due to basal overpressure. Water is pumped through a bed comprising two particle diameters (36 micron and 689 micron in 2:3 ratio; 20% of coarse particles dyed blue to aid visualisation). This models processes forming a sediment extrudite (e.g. sand volcanoes, blows or boils).

This was the first video I took of the capabilities of Flowave taken shortly after it opened. It has generated over 900,000 hits on YouTube. The principles of 3D wave generation were researched back in the early 80's by Ian Bryden and myself [Bryden, I.G. and C.A. Greated (1984) ‘Generation of 3-dimensional random waves’ Journal of Physics D – Applied Physics 17(12), 2351-2366]

A large amplitude internal solitary wave (ISW) in the laboratory. The ISW is subject to a shear force across its centre. If the shear is strong enough, the ISW breaks and Kelvin-Helmholtz billows are induced as shown. Visualisation is of neutrally buoyant (light-reflecting) tracer particles suspended in brine solution.

The video shows the 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.

Our projects are concerned with the study of turbulent buoyant flows structure and dynamics. This video aims at presenting artistically the beauty of turbulent buoyant flows evolution in time and space. We will be using visualization methods to present plumes, gravity currents and vortex rings, sometimes making them interact with each other.

Through intelligent processing of flame images, the weak chemiluminescence can be visualised under direct high-speed imaging. Meanwhile, the flame infrared emission features have been captured for the first time. As a result, multiple flame light emission from visible to infrared spectrum can be visualised simultaneously in the flame ignition process.

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. The video is not a composite and has not been enhanced.

The video is a combination of data from simulations and experiments on tandem flapping flippers. Some enhancements (adjustments of levels and brightness) have been done.

Slice from a 3D two-way coupled DNS homogeneous isotropic turbulent flow containing 35 million solid particles. The background represents the Okubo-Weiss parameter, with particles avoiding red zones (vorticity overwhelms strain) and concentrating in the blue regions (the opposite). Taylor Reynolds is 35.4, Stokes 0.2, mass loading 0.5 and total time 1.1s.

The flow driven by a rotating impeller inside an open fixed cylindrical cavity is studied numerically using the code BLUE, a solver for massively parallel simulations of fully three-dimensional multiphase flows. The impeller is composed of four blades at a 45 degree inclination all attached to a central hub and tube stem. In BLUE, solid forms are constructed by means of a module for the definition of immersed objects via a distance function that takes into account the object's interaction with the flow for both single and two-phase flows. The fluid interface solver is based on a parallel implementation of a hybrid Front Tracking/Level Set method designed to handle highly deforming interfaces with complex topology changes. Parallel GMRES and multigrid iterative solvers are applied to the linear systems arising from the implicit solution for the fluid velocities and pressure in the presence of strong density and viscosity discontinuities across fluid phases.

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.

$A fluid-driven fracture propagates radially in a transparent hydrogel. The fracture surface post experiment consists of beautiful fractal patterns called step-lines. These are small changes in height along the surface of the gel, which follow a logarithmic spiral shape. (No adjustments were made to the image.)$

The image comprises a mixture of two liquid crystal mesogens cooling under polarizing optical microscopy. One of the mesogens forms an intertwining polymer network, which can be seen nucleating from individual sites. The solid polymer matrix propagating through the sample develops a complex interface with the fluid liquid crystal.

A fluid flow drives the migration of a sand dune. Particles are entrained on the upstream slope and roll/jump to the crest where they avalanche or are ejected into the flow. The internal part of the dune behaves like a solid whereas the moving layer of particles is fluid-like.

A 36mm-diameter, 1mm cross-section Latex ring floats on the surface of the water in a funnel. The water is slowly removed, the surface area decreases and the ring is compressed and buckles into a 'yin yang' shape.

A solid sphere wrapped up in a thin polymer sheet and hanging from an air-liquid interface. The sphere had impacted a floating sheet but didn't submerge it, and now surface tension acting on the film boundary balances the negative buoyancy of the sphere, so it's 'hanging out' in the liquid.

'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. (Minor brightness and contrast adjustments).

An experimental investigation is carried out to study particle entrainment processes (including rolling, hopping and saltation) under well controlled conditions, for a number of particle densities (rho_s>1100kg/m^3), flow regimes (Re>10^6) and bed roughness arrangements.

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 due to an interplay between the elasticity of the sheet and the inertia of the fluid.

This is a video showing a liquid droplet rolling up on a flexible microfluidic device, in which droplet flows along the slope formed by simply bending-deforming a 600 micron thick aluminium (Al) plate. The droplet was remotely pushed up by the acoustic wave propagating along the Al plate surface, which is generated by a thin layer of ZnO film (with electrode onto it).

An 18mm-diameter, 1mm cross-section Latex ring floats on the surface of the water in a funnel. The water is slowly removed, the surface area decreases and the ring is compressed and buckles.

A solid sphere impacts a thin polymer sheet floating at an air-liquid interface. The video is slowed down 200 times.

This video shows the transfer of mechanical energy and radiative pressure from Surface Acoustic Wave (SAW) travelling onto 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.

This is a video of a novel experiment where photoelastic discs are rolled down a narrow, inclined chute. Here the forces exerted when discs interact can be measured from the intensities of the light they transmit with the aim of investigating how stresses are distributed within avalanches.

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.

A stream of ambient air flows uniformly through the bottom of a shallow granular layer. The flow oscillates and the periodic perturbation to the energy input into the granules transforms into a spatiotemporal pattern due to the energy dissipated through inelastic collisions. (Minor adjustments made to enhance brightness and contrast).

This image from a 3D immersed-boundary lattice-Boltzmann simulation vividly depicts a suspension of deformable red blood cells travelling through a bifurcating blood vessel. The RBCs are immersed in a Newtonian plasma. The main branch of the blood vessel is 96-micrometer wide, and the child branches are 50-micrometer wide.

This is an image captured from a high speed video showing jetting behaviour of a 5uL water droplet induced by ZnO surface acoustic waves (two waves from both sides). The vertical jetting is induced by sub-nanometre amplitudes of surface acoustic waves propagating on a ZnO coated silicon device, interacting with water droplet from both sides. Before the liquid beam breaks up, it forms a shape of crystal snake-like structure.

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.

The colour-enhanced high-speed image illustrates a high velocity water jet breaking a stream of kerosene by inducing waves, which can cause oil ligament breakup and drop detachment. The mirrored images of these generated waves can have forms, which to the pattern-seeking human eye can transform into familiar yet unexpected figures.

A composite image comparing the visible and infrared, showing the aftermath of a cold droplet impacting on a hot film. Linear features due to the uneven mixing are visible in the infrared image.

$A fluid-driven fracture propagates radially in a transparent hydrogel. The fracture surface that is revealed post-experiment consists of beautiful fractal patterns called step-lines. These are small changes in height along the surface of the gel, which follow a logarithmic spiral shape. (Raw image)$