State of shock: 200-year-old law about gas mixtures called into question

December 11, 2019

According to a new study led by a team from The University of New Mexico, centuries-old laws about the behavior of gas mixtures do not apply in the presence of shock waves.

This finding could have potential impact on everything that involves mixtures of gases exposed to a shock wave, for example, during combustion in an engine. This is also relevant for conventional and nuclear explosions, supersonic jets, gas-cooled nuclear reactor plants and inertially-confined fusion.

The results were published recently in the paper "Dalton's and Amagat's Laws Fail in Gas Mixtures with Shock Propagation" in Science Advances. Authors on the paper are Patrick Wayne, Daniel Freelong, Gregory Vigil, Timothy Clark, Peter Vorobieff and C. Randall Truman from the Department of Mechanical Engineering at UNM; Sean Cooper, J. Mike Walker '66 Department of Mechanical Engineering, Texas A&M University; Dylan Simons, Department of Aeronautics and Astronautics, Air Force Institute of Technology; Ignacio Trueba-Monje, Aerospace Engineering Department, The Ohio State University; and Vladimir Vorob'ev, Joint Institute for High Temperatures, Russian Academy of Science.

The study, conducted at UNM, involved pre-mixing two gases with dramatically different properties: light helium and heavy and viscous sulfur hexafluoride. The team characterized the properties of the resulting mixture, which agreed well with classical theory, then a shock wave was introduced, and the temperature and pressure of the shock-accelerated medium were measured over several milliseconds - a short time to think of in normal terms, but a long interval compared with the time scales associated with the shock wave passage. The researchers found that the temperature and pressure after the shock compression did not line up with what would have been expected from the predictions of either of the two classical theoretical laws - Dalton's or Amagat's.

French physicist Emile Hilaire Amagat's law of partial volumes from 1880 states that the total volume of a gas mixture is equal to the sum of the partial volumes each gas would occupy if it existed alone at the temperature and pressure of the mixture. And in 1802, scientist John Dalton stated that the total pressure in a non-reactive gas mixture - at constant temperature and volume - is equal to the sum of the partial pressures of the component gases.

"Our study found that classical laws used to predict gas mixture properties fail to work in a fairly common and practically important situation," Vorobieff said.

The reason for disagreements is that neither classical law can accurately describe what happens on the molecular level, he said. Simple considerations of time scales from kinetic molecular theory, and how they are affected by shock acceleration, appear to provide at least a qualitative explanation of the experimental observations. Vorobieff said that although this is a solid first step, the ultimate implications have not yet been determined, and much further study is required. Possible impacts could mean a design change in mechanisms like engines that take into account how shock waves affect the gas mixture properties.

"Our work has shown that classical gas mixture theory does not work in shock-accelerated and possibly other compressible flows," Vorobieff said. "We must conduct experiments with more gas mixtures and a broader range of conditions to explore the scope of the problem and develop a theory explaining our observations."
-end-
Funding for this project was provided by the National Nuclear Security Administration.

University of New Mexico

Related Nuclear Articles from Brightsurf:

Explosive nuclear astrophysics
An international team has made a key discovery related to 'presolar grains' found in some meteorites.

Nuclear medicine and COVID-19: New content from The Journal of Nuclear Medicine
In one of five new COVID-19-related articles and commentaries published in the June issue of The Journal of Nuclear Medicine, Johnese Spisso discusses how the UCLA Hospital System has dealt with the pandemic.

Going nuclear on the moon and Mars
It might sound like science fiction, but scientists are preparing to build colonies on the moon and, eventually, Mars.

Unused stockpiles of nuclear waste could be more useful than we might think
Chemists have found a new use for the waste product of nuclear power -- transforming an unused stockpile into a versatile compound which could be used to create valuable commodity chemicals as well as new energy sources.

Six degrees of nuclear separation
For the first time, Argonne scientists have printed 3D parts that pave the way to recycling up to 97 percent of the waste produced by nuclear reactors.

How to dismantle a nuclear bomb
MIT team successfully tests a new method for verification of weapons reduction.

Material for nuclear reactors to become harder
Scientists from NUST MISIS developed a unique composite material that can be used in harsh temperature conditions, such as those in nuclear reactors.

Nuclear physics -- probing a nuclear clock transition
Physicists have measured the energy associated with the decay of a metastable state of the thorium-229 nucleus.

Milestones on the way to the nuclear clock
For decades, people have been searching for suitable atomic nuclei for building an ultra-precise nuclear clock.

Nuclear winter would threaten nearly everyone on Earth
If the United States and Russia waged an all-out nuclear war, much of the land in the Northern Hemisphere would be below freezing in the summertime, with the growing season slashed by nearly 90 percent in some areas, according to a Rutgers-led study.

Read More: Nuclear News and Nuclear Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.