Neat stuff in the lab: Some results

Bubbles below sloping surfaces

Shape of a bubble (water) rising through a much more viscous and miscible fluid (corn syrup) and below a sloping surface. From the work of Jim Watkins and Chris Huber.

Set up for the bubble experiment.

Wax tectonics

IR (8-14 micron) image of triangular rifts. Black is hot (molten wax), white is colder (thick, solid wax).

Photograph of surface features formed on a periodically deformed layer of solid wax (see Manga and Sinton (2004) for details). These experiments were designed to better understand the conditions and dynamics that lead to the formation of lineaments on Jupiter's icy satellites (e.g., bands and rirdges on Europa). Similar wax experiments have provided insight into mid ocean ridge structure (Oldenburg and Brune, 1972, 1975; Ragnarsson et al., 1996).

Decompression experiments and explosive eruptions

These experiments were designed and performed by Atsuko Namiki. The set up is shown below.

Click to see MOVIE (reduced resolution but still 10 Mb) of some experiments. In these movies you are watching the response of a bubbly fluid to rapid decompression; each panel shows only the shock tube. 2000 frames are capture per second, and the whole movie last about 20 milliseconds. From top to bottom, the initial bubble content decreases. Only in the top experiment does the fluid erupt explosively from the sample holder.

Convection in stably stratified fluids

The picture above shows an oblique few of a dense layer of (red) vegetable oil beneath a (colourless) layer of miscible polybutene oil -- this setup may be analogous to the situation in the Earth's lower mantle where a compositionally distinct dense layer (due to partial melt, the presence of metals, or the segregation of subducted materials) appears to exist. The dynamic and thermal coupling of the dense layer with the overlying fluid allows persistent plume conduits (right) to form and stabilizes the location of these conduits. From Jellinek and Manga, Nature 2002; see press release for another explanation.

In this photograph light, low viscosity (input) fluid is released at a fixed but slow rate through a permeable plate into an overlying denser layer of very viscous (ambient) fluid. Convection takes the form of plumes with large spherical heads and narrow trailing conduits. Upwelling input fluid passes through the ambient layer and ponds without causing any significant mixing. From Jellinek, Kerr and Griffiths.

Light low viscosity fluid is released at a very high rate into an overlying dense more viscous fluid. Upwelling fluid entrains ambient fluid, thereby driving large-scale turbulent circulation. The resulting overturning motions produce extensive mixing and no stratification. From Jellinek, Kerr and Griffiths. 

Big tanks

Above we show a series of experiments showing the influence of imposed large-scale circulation on thermal convection from a hot boundary in a fluid with a temperature-dependent viscosity (corn syrup). The opposing motions of two conveyor belts immersed in the syrup at the top of the tank are used to generate a large-scale flow that is divergent at the center of the tank and convergent at the tank walls. On the right we show the details of the upwelling region. The Rayleigh number is a crude measure of the vigor of convection from the bottom of the tank. The velocity ratio is the ratio of the imposed horizontal flow velocity to the rise speed of plumes ascending from the hot boundary. The viscosity ratio is the ratio of the viscosity of the interior fluid to the viscosity of the syrup in contact with the hot boundary. From Jellinek, Gonnermann and Richards.

Suspensions and particulate flows

Rising bubbles in corn syrup. Re < 0.001. The Bond number, the ratio of buoyancy to surface
tension stresses, is about 40. Photographs are taken a 5 second intervals.
Bubble radii about about 1 cm. See Manga and Stone, J. Fluid Mech. 1993 and 1995 for more details.

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