UKFN Videos 31/7/17 shortlist: Recent Episodes
Cambridge University
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.
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 video is a combination of data from simulations and experiments on tandem flapping flippers. Some enhancements (adjustments of levels and brightness) have been done.
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.
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.
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.
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.
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.
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]
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).