There are two categories of fluids: regular ones and weird ones. Water and alcohol act more or less as expected when pumped through pipes or stirred with a spoon. There are a lot of behavioral mysteries that have stumped researchers over the centuries.
A long-standing puzzle was first articulated nearly 55 years ago when certain liquids stream through cracks and holes in a porous landscape. The liquid will flow normally. It will pass a critical threshold as its flow rate increases, where it will suddenly coalesce, shooting up like a martini.
A new study shows that the effect on tiny molecule suspended in the fluid that whirl and stretch as the flow rate increases. The fluid flow becomes chaotic, surging and rippling in convoluted eddies that loop back to themselves at some point. Chaos impedes the fluid's movement. The finding could have applications in a number of areas.
The manuscript is beautiful, according to a University of Pennsylvania researcher who wasn't involved in the work.
In the 1960s, the rheologist Arthur Metzner and his undergraduate student Ronald Marshall were working on oil fields, where engineers would often inject water mixed with so-called pusher fluids into the ground to displace the oil and help extract every drop of crude. The scientists noticed that when the pusher fluid was pumped into the ground above a certain rate, it seemed to suddenly become sticky.
One of the most important things you want to be able to predict and control isosity, according to Sujit Datta, a chemical engineer at Princeton University who came across the paper by Marshall and Metzner. Even after decades of research, we still don't know why the viscosity is what it is and how to explain the increase.
Pusher fluids and other viscoelastic fluids can contain long, complex molecules. Scientists thought that the molecule might be piling up in the ground, like hair in the drain. They realized that these weren't easy to fix. The obstruction disappeared completely when the rate of flow fell below a critical threshold.
A group at the Gould Research Center in Cambridge, England, simplified the problem in 2015. The researchers built a two-dimensional analogue of sandy soil with sub millimeter-size channels leading into a labyrinth of cross-shaped pieces. They pumped the fluids into the system. The team noticed that the fluid movement became messy and disorganized in the spaces between the crosses, which slowed the motion of the liquid.
It should be almost impossible. inertia is the main influence on regular fluids' tendency to keep flowing. Water has a lot of inertia. As water moves faster and faster, small streams within the flow will start to overtake other sections of the fluid, leading to chaotic eddies.
A fluid like honey has very little inertia. It will stop flowing when you stop stirring it. inertial turbulence is the ordinary kind of turbulence that happens in a rushing stream or beneath an airplane's wings.
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