Stokes Paradox: How small particles move in water
Consider a snow globe. When shaken, the tiny flakes and particles are set into motion and “it snows”. What lights up kid’s eyes has been a long standing puzzle for scientists, as there has been no consensus on how particles with shapes other than spheres, for example cylinders, settle though water.
This problem is, however, of great relevant and finds application also in the climate research. Now, scientists from Max Planck Institute for Marine Microbiology, Germany have shed light onto this problem, and present a solution.
Scientists, for example, climate researchers and engineers are interested in the sinking of particles in water columns of lakes and oceans. These particles can appear in the form similar to sphere, cylinder and other shapes. Cylindrical organisms with a large length to diameter ratio are quite ubiquitous in the world’s oceans. Such examples are diatoms, fecal pellets and green algae.
The British scientist Sir George Gabriel Stokes found in 19th century a relation for the drag experienced by a solid sphere moving in viscous fluid. Nevertheless, he failed to obtain a solution for a solid cylinder, He further postulated that a rigorous mathematical solution for this problem does not exist, which was referred to as “Stokes’ Paradox” by subsequent researchers. Until now, all approximations presented deviated drastically from one another. Areal consensus appeared unachievable.
While studying the sinking behavior of the dead marine organisms to the sea floor, Arzhang Khalili and Bo Liu from the Max Planck Institute for Marine Microbiology in Bremen found a solution to “Stokes’ Paradox”, and present their results in the Journal of Fluid Mechanics.
How quickly particles sink to the sea floor is of interest to climate researchers, because microorganisms contain bound carbon, which originate from microscopic organisms using photosynthesis. The necessary carbon dioxide comes from the atmosphere.
“With the relation presented by us one can one can calculate carbon balances more accurately’’, says Arzhang Khalili, also Adjunct Professor at Jacobs University Bremen. “When we compared the different available solution of Stokes’ paradox with experimental data no agreement could be found. Only extensive and accurate numerical computer simulation led to successful results.”
And what about the snow globe? One can enjoy watching it without mathematics.
Khalili, A., & Liu, B. (2017). Stokes’ paradox: Creeping flow past a two-dimensional cylinder in an infinite domain. Journal of Fluid Mechanics, 817, 374-387. doi:10.1017/jfm.2017.127
Questions maybe addressed to:
Prof. Dr. Arzhang Khalili
Max-Planck-Institut für Marine Mikrobiologie
Celsiusstraße 1, 28359 Bremen Telefon: +49 421 2028 636
or to the press office
Dr. Manfred Schlösser
Dr. Fanni Aspetsberger
Phone: +49 421 2028 704
Dr. Manfred Schloesser | Max-Planck-Institut für marine Mikrobiologie
Protein interaction helps Yersinia cause disease
21.08.2018 | Schwedischer Forschungsrat - The Swedish Research Council
Nanobot pumps destroy nerve agents
21.08.2018 | American Chemical Society
There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.
The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...
New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference
Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
17.08.2018 | Event News
08.08.2018 | Event News
27.07.2018 | Event News
21.08.2018 | Power and Electrical Engineering
21.08.2018 | Life Sciences
21.08.2018 | Medical Engineering