Behold the Mayo: Researchers Reveal 'Instability Threshold' of Elastic-Plastic Material Using Hellmann’s Real Mayonnaise

Professor Arindam Banerjee’s Rayleigh-Taylor-instability experiments confirm that the instability of elastic-plastic material is a function of initial conditions, such as amplitude and wavelength.

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Lori Friedman

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iStock-Media Production

Arindam Banerjee, associate professor of mechanical engineering and mechanics, studies the dynamics of materials in extreme environments. He and his team have built several devices to effectively investigate the dynamics of fluids and other materials under the influence of high acceleration and centrifugal force.

One area of interest is Rayleigh-Taylor instability, which occurs between materials of different densities when the density and pressure gradients are in opposite directions, creating an unstable stratification.

“In the presence of gravity―or any accelerating field―the two materials penetrate one another like ‘fingers,’” says Banerjee.

According to Banerjee, the understanding of the instability is mostly confined to fluids (liquids or gases). Not much is known about the evolution of the instability in accelerated solids. The short time scales and large measurement uncertainties of accelerated solids make investigating this kind of material very challenging.

Jar of Hellmann's Real Mayonnaise

The results of Banerjee's experiments using mayonnaise could apply to high-energy density physics problems relevant to inertial confinement fusion.

In the experiments, Hellmann’s Real Mayonnaise was poured into a Plexiglass container. Different wave-like perturbations were formed on the mayonnaise and the sample was then accelerated on a rotating wheel experiment. The growth of the material was tracked using a high-speed camera (500 fps). An image-processing algorithm, written in Matlab, was then applied to compute various parameters associated with the instability. For the effect of amplitude, the initial conditions were ranged from w/60 to w/10, while the wavelength was varied from w/4 to w to study the effect of wavelength (“w” represents the size of the width of the container). Experimental growth rates for various wavelength and amplitude combinations were then compared to existing analytical models for such flows.

This work allows researchers to visualize both the elastic-plastic and instability evolution of the material while providing a useful database for development, validation and verification of models of such flows, says Banerjee.

He adds that the new understanding of the “instability threshold” of elastic-plastic material under acceleration could be of value in helping to solve challenges in geophysics, astrophysics, industrial processes such as explosive welding, and high-energy density physics problems related to inertial confinement fusion.

Understanding the Hydrodynamics of Inertial Confinement

Banerjee works on one of the most promising methods to achieve nuclear fusion called inertial confinement. In the U.S., the two major labs for this research are the National Ignition Facility at the Lawrence Livermore National Laboratory in Livermore, California—the largest operational inertial confinement fusion experiment in the U.S.—and the Los Alamos National Laboratory in New Mexico. Banerjee works with both. He and his team are trying to understand the fundamental hydrodynamics of the fusion reaction, as well as the physics.

Story by

Lori Friedman

Photography by

iStock-Media Production

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