Unusual thermal convection in a well-mixed fluid

December 15, 2017, Tokyo Metropolitan University
Pattern evolution during thermal convection in a mixture of two silicone oils, with viscosities 1cs and 100cs. An immobile region is formed and the macroscopic flow of the entire system changes drastically. Because temperature-dependence on viscosity is very small, a pillar-shaped stagnant domain is formed over the whole region where the fluid wells upwards. Credit: Kazuya U. Kobayashi and Rei Kurita

Researchers from Tokyo Metropolitan University, have recently discovered unusual thermal convection in a uniform mixture of high- and low-viscosity liquids. Kobayashi and Kurita found that concentration fluctuations are enhanced by thermal convection when the two liquids have a large viscosity difference. Such mixtures are ubiquitously observed in nature, daily life, and manufacturing processes e.g. mantle convection, syrup, polymer products. These results promise further insight into non-equilibrium phenomena in fluid mixtures with contrasting "thickness."

When a is heated from below, thermal is usually driven by a density difference. Kobayashi and Kurita found that immobile regions are transiently formed during thermal convection in well-mixed two component liquids with a large viscosity difference. They investigated the convection patterns and dynamics using several different combinations of liquids. They concluded that the viscosity difference is one of the most important factors for the formation of these static regions. This suggests that the viscosity difference plays an important role in non-equilibrium phenomenon in fluid mixtures, such as in the dynamics of convection in the mantle, mixing processes in polymer solutions, etc.

The research group of Kazuya U. Kobayashi (PhD student) and Rei Kurita (Associate Professor) specializes in experimental studies of thermal convection. In 2015, they discovered the formation of a transient stagnant domain in a gelatin solution near the sol-gel (fluid-solid) transition. In this work, they identified the critical condition required for the phenomenon using several different kinds of fluid: they concluded that the stagnant domain is generally formed when the mixture features a large viscosity difference. Prof. Kurita notes that "although this unusual phenomenon is only observed in , the difference between components should play an important role in the dynamics of fluid mixtures, such as in , mixing processes, etc." The report holds great promise for progress in our understanding of fluid dynamics, earth sciences, and meteorology.

This study was supported by Grants-in-Aid for Scientific Research of the Japan Society for the Promotion of Science. The manuscript reporting this finding has been published online in Scientific Reports.

Explore further: A new type of convection is proven in granular gases

More information: Kazuya U. Kobayashi et al, Ubiquitous transient stagnant domain formation during thermal convection in a well-mixed two component fluid with large viscosity difference, Scientific Reports (2017). DOI: 10.1038/s41598-017-13409-w

Related Stories

A new type of convection is proven in granular gases

November 14, 2016

In physics, thermal convection of a fluid is exhibited by the appearance of geometric structures through which the fluid moves, forming closed circuits. This phenomenon is of vital importance for many industrial applications ...

Bacteria used to create superfluids

July 13, 2015

(Phys.org)—A team of researchers with Université Paris-Sud and Université P.M. Curie/Université Paris-Diderot, both in France, has discovered that putting certain types of bacteria into an ordinary fluid, can cause it ...

Chemical reactions can be self-stirring (w/ Video)

February 1, 2010

(PhysOrg.com) -- Every chemistry student knows that if you stir a mixture of chemicals you speed up the reactions between them, but less well-known is that chemical reactions can themselves stir up the mixture. This was demonstrated ...

Recommended for you

New thermoelectric material delivers record performance

January 17, 2019

Taking advantage of recent advances in using theoretical calculations to predict the properties of new materials, researchers reported Thursday the discovery of a new class of half-Heusler thermoelectric compounds, including ...

Zirconium isotope a master at neutron capture

January 17, 2019

The probability that a nucleus will absorb a neutron is important to many areas of nuclear science, including the production of elements in the cosmos, reactor performance, nuclear medicine and defense applications.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.