Megan S. Davies Wykes


Rayleigh-Taylor instability


Rayleigh-Taylor instability occurs between fluids of different densities. In the images below the green dyed fluid is less dense than the un-dyed fluid. A video of this instability can be found on YouTube. Images taken during my PhD, supervised by Prof Stuart Dalziel.

Rayleigh-Taylor instability Rayleigh-Taylor instability Rayleigh-Taylor instability

Rayleigh-Taylor instability in a stratification


Shadowgraphs of Rayleigh-Taylor instability between two stratified layers. A barrier is withdrawn from right to left and a turbulent mixing region develops. Images are shown at 5, 10, 20 and 80 seconds. At late-time stratifications remain above and below a mixed region. Images taken during my PhD, supervised by Prof Stuart Dalziel.


The same experiment can also be viewed using dyed layers.


Dissolution of sphere


Shadowgraphs of a sphere made of hard candy, dissolving in water. Fluid with a higher concentration of sugar is more dense than the ambient, therefore a buoyancy-driven flow is set up. This affects the evolving shape of the sphere, smoothing the upper surface and roughening the underside. Images taken during my postdoc at NYU, work in collaboration with Prof Leif Ristroph and Mac Huang.

Dissolution roughness


A dissolving surface is roughened when the concentration boundary layer is gravitationally unstable. The instability results in covection of fluid away from the surface in the form of small plumes, which roughen the surface. Images taken during my postdoc at NYU, work in collaboration with Prof Leif Ristroph and Mac Huang.

Dissolution roughness
Dissolution roughness

Splash thrown from a rotating disc

Varying rotation speed

These images show the splash thrown out by a rotating wheel which is partially submereged in water. As the rotation speed of the wheel is increased more water is thrown from the wheel and the film becomes increasingly unstable. Images of experiments performed by Anna Skipper, a PhD student I supervised at the Geophysical Fluid Dynamics Programme in 2016. A video of this flow was submitted to the American Physical Society Gallery of Fluid Motion the same year.

Comparison of water and fluid with finite yield stress

These images show the splash thrown out by a rotating wheel which is partially submereged in either water or a non-Newtonian fluid with a finite yield stress, chosen to model mud. At low rotation speeds the flow looks very similar, but at higher speeds the film thrown from the non-Newtonian experiment breaks up, creating a great deal of splash. Images of experiments performed by Anna Skipper, a PhD student I supervised at the Geophysical Fluid Dynamics Programme in 2016. A video of this flow was submitted to the American Physical Society Gallery of Fluid Motion the same year.

Double diffusive instability


Double diffusive instability occurs when there are two components to the density field, in this case, the temperature and salinity of the water. Overhead lamps preferentially heat the green-dyed fluid, making it less dense, such that it rises in the form of a thin plume. The heat quickly diffuses into the surrounding fluid, leaving fluid within the plume with a higher salinity than the surroundings.

Double diffusive instability
Double diffusive instability

Other


Candy image
Candy image