The photographs on this page relate to our papers:
O.A.M. Boote and P.J. Thomas, "Effects of Granular Additives on Transition Boundaries Between Flow States of Rimming Flows," Phys. Fluids
P.J. Thomas, G.D. Riddell, S. Kooner and G.P. King "Fine Structure of Granular Banding in Two-Phase Rimming Flow," Phys. Fluids
The pictures originate from an experiment in which we study the various flow states of a fluid (silicon oil) inside a partially filled, horizontal rotating cylinder . Which state is displayed depends on the rotation rate and the filling level etc....
"Nothing new..." I hear you mumble. Well, the new aspect of our experiment is that we introduced successively increasing amounts of 'dirt' (or as we like to call it in a more fancy way, 'granular additives') to the fluid inside the cylinder. The purpose being to investigate how these granular additives would affect the transition boundaries between different flow states such as those shown below. Ok, now go away read our paper and then come back to have a look at the pictures....
Welcome back! After having read the paper we trust you will understand what follows below....
Here you see the wavy front, which is displayed at low rotation rates. This is a side view of the wavy(?) front . After increasing the rotation rate a bit the wavy front breaks up and develops into u-shaped structures, which then, in turn, develop into a cellular structure after increasing the rotation rate further. Under certain conditions one gets ... cascades ,... ... cascades ,... ... cascades ... and more cascades .
After adding a certain critical amount of granular materials one gets granule band formation, with varying numbers of granule bands depending on the exact experimental conditions. Here are some more bands ,... ... and some more bands ... and some more bands .
If one uses two different size classes of spherical granules at the same time then the bands look like this . Here is a magnified view of this; the larger particles are red and the smaller ones are yellow.
And here comes the highlight! If one uses the right type of particles then the granule bands develop a secondary instability displaying a fine structure . Here you can see a magnified view of the fine structure .