Behold the mayo: Experiments reveal ‘instability threshold’ of elastic-plastic material

Rayleigh-Taylor-instability experiments confirm that the instability of elastic-plastic material is a function of initial conditions, such as amplitude and wavelength; characterization could apply to problems relevant to inertial confinement fusion

Lehigh University

These are experimental images for 3D initial perturbation. Credit Arindam Banerjee

These are experimental images for 3D initial perturbation. Credit Arindam Banerjee

Arindam Banerjee, an associate professor of mechanical engineering and mechanics at Lehigh University, 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.

Banerjee and his team have succeeded in characterizing the interface between an elastic-plastic material and a light material under acceleration. They discovered that the onset of the instability?or “instability threshold”?was related to the size of the amplitude (perturbation) and wavelength (distance between crests of a wave) applied. Their results showed that for both two dimensional and three dimensional perturbations (or motions) a decrease in initial amplitude and wavelength produced a more stable interface, thereby increasing the acceleration required for instability.

These results are described in a paper published today in Physical Review E called “Rayleigh-Taylor-instability experiments with elastic-plastic materials.” In addition to Banerjee, co-authors include Rinosh Polavarapu (a current Ph.D. student) and Pamela Roach (a former M.S. student) in Banerjee’s group.

“There has been an ongoing debate in the scientific community about whether instability growth is a function of the initial conditions or a more local catastrophic process,” says Banerjee. “Our experiments confirm the former conclusion: that interface growth is strongly dependent on the choice of initial conditions, such as amplitude and wavelength.”

In the experiments. Hellman’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.

In inertial confinement experiments, the gas (hydrogen isotopes, like in magnetic fusion) is frozen inside pea-sized metal pellets. The pellets are placed in a chamber and then hit with high-powered lasers that compress the gas and heat it up to a few million Kelvin–about 400 million degrees Fahrenheit–creating the conditions for fusion.

The massive transfer of heat, which happens in nanoseconds, melts the metal. Under massive compression, the gas inside wants to burst out, causing an unwelcome outcome: The capsule explodes before fusion can be reached. One way to understand this dynamic, explains Banerjee, is to imagine a balloon being squeezed.

“As the balloon compresses, the air inside pushes against the material confining it, trying to move out,” says Banerjee. “At some point, the balloon will burst under pressure. The same thing happens in a fusion capsule. The mixing of the gas and molten metal causes an explosion.”

To prevent the mixing, adds Banerjee, you have to understand how the molten metal and heated gas mix in the first place.

To do this, his group runs experiments that mimic the conditions of inertial confinement, isolating the physics by removing the temperature gradient and the nuclear reactions.

Banerjee and his team have spent more than four years building a device specifically for these experiments. Housed on the first floor of Lehigh’s Packard Laboratory, the experiment is the only of its kind in the world, as it can study two-fluid mixing at conditions relevant to those in inertial confinement fusion. State-of-the-art equipment is also available for diagnosing the flow. The projects are funded by the Department of Energy, Los Alamos National Laboratory and the National Science Foundation.

One of the ways that researchers like Banerjee mimic the molten metal is by using mayonnaise. The material properties and dynamics of the metal at a high temperature are much like those of mayonnaise at low temperature, he says.

The team’s device re-creates the incredible speed at which the gas and molten metal are mixing. They gather data from the experiments they run and then feed it into a model being developed at Los Alamos National Lab.

“They have taken a very complicated problem and isolated it into six or seven smaller problems,” explains Banerjee. “There are materials scientists working on certain aspects of the problem; there are researchers like me who are focused on the fluid mechanics–all feeding into different models that will be combined in the future.”


From EurekAlert!

34 thoughts on “Behold the mayo: Experiments reveal ‘instability threshold’ of elastic-plastic material

  1. “…the two materials penetrate one another like ‘fingers,’” says Banerjee.”…
    “Hellman’s Real Mayonnaise was poured into a Plexiglass container. “…
    ” The growth of the material was tracked using a high-speed camera (500 fps).”

    … because … Science. Ya’ that’s the ticket.

    These guys have a future in the porn industry if physics leaves them without a paycheck.

  2. Interesting for plastics, yet will not help fusion.
    They do need a 20x larger laser at NIF to have ignition.

    • Getitright?

      Where did that come from? The three laws of plumbing are:

      Water flows downhill
      Shit floats
      Payday’s Thursday

      That’s all you need to know. The rest is derived from those foundational truths.

      For fusion the following applies:

      Make it hot enough, it gets hotter by itself
      It’s only 30 years from commercialisation
      We need a bigger laser/magnet/budget
      Watch this! (Stand well back)

  3. Explosion welding produces a wave pattern resembling those pictured above.

    A search for explosion welding ppt will give some insight on the process.

    • The first take is that strange things happen when conditions are extreme.
      In order to get results you need to do experiments, which will require extreme machines. You can’t experiment with a process that takes 3 milliseconds using a stop watch. The equipment is going to cost much more than watching paint dry.

      The compression, or inertia containment, fusion scenario is very interesting because it is the most likely to get results. All of the Tokamak type experiments have been 20-30 years from break even and cost trillions dollars since they started. The inertia devices can be built much smaller because of “physics”.

  4. Interesting article – thanks.

    As soon as I started into it I thought this is about inertial containment fusion or nuclear weapons.

    Unfortunately it seems to demonstrate a serious stumbling block to the inertial containment idea.

    Ah well another piece of information to add to a head full of (mostly) useless information.

  5. And when you have finished your experiment, you can dress a salad with it….

  6. I also use Hellman’s Real Mayo in my Mr. Fusion, not only does the aroma from it make me hungry, it provides all of the electricity I need, especially to run the electric stove to fry my bacon and the toaster to make my toast. That BLT is a wonderful byproduct..

    Strangely, I’m hungry right now…

  7. I am a little baffled by this because it seems to me this has been known since the development of implosion ignition of fission devices during the Manhattan project. Is this really surprising?

  8. Fusion is really quite straightforward.
    All they have to do is replicate the gravitational force of the sun.
    The other day, just for the fun of it I bought a small jar of “Miracle Whip”.
    Still good.

    • Have to disagree with you there Bob. Miracle Whip is one nasty product. I believe it is made from used motor oil and industrial emulsifier, isn’t it? I could be mistaken 🙂

      As for fusion, well we will definitely have fusion power on earth when the sun goes red giant and engulfs us. And the researchers will still be sucking down funding right up to then, always promising 30 years to commercialization +/-25 years.

    • well sure, if 222 is “a few”, right?

      It is EurekAlert! after all. The strange thing is, nowhere did it say “With a warming climate…”

  9. “Our experiments confirm the former conclusion: that interface growth is strongly dependent on the choice of initial conditions, such as amplitude and wavelength.”

    it’s as much dependent on the conditions thereafter also, like acceleration rate and sustained velocity.

    In all cases the initial conditions will, in combination with changing parameters in environment, determine the outcome 😀

    Reading through, seems this is not even a step toward FP, it’s a guess that it might be a step 🙂

    • Mark,
      In the eschatology of the CC religion, fusion power is analogous to the hope for unending life after death. We will have to sacrifice now with windmills and solar panels, but it will all be worth it when fusion comes in glory to judge the green and the woke.

      We gotta do SOMETHING! Fusion is the hope of salvation. So it’s a crisis to be exploited for grant money. My left-handed screwdriver design might help with assembling superconducting magnets on tokamaks to achieve commercial fusion power. I can possibly finish my design with another $10 million.

  10. Uh…So they are solving the Fusion Power problem by using “Hellman’s Real Mayonnaise”? Hmmm…

    OMG! Does the U.S. have enough “Hellman’s Real Mayonnaise” to be energy independent? Or has China already secured all the main sites where “Hellman’s Real Mayonnaise” is mined? This could be a HUGE security threat.

    I think the House of Representatives should form an investigative committee immediately and then blame someone they don’t like.

    (Mayonnaise??? Really? This has got to be another of those research paper spoofs…)

    • Research Paper spoof… I think you nailed it.

      There is nothing at all surprising regarding this paper except it was accepted and published.

  11. We won’t know if their results are solid until they are replicated with several other brands of mayo such as Sir Kensington’s, Duke’s, Thomy’s, Heinz’, etc all of whom produce “real mayonnaise.

  12. “Experiments reveal ‘instability threshold’ of elastic-plastic material”:

    could also be interesting for meteorology, behavior of snow / ice / mixtures:

    Stiffness, toughness, flowing behavior,

    break, demolition on terrain edges …, –> avalanches : reach of snow distribution, velocities, dissemination. …


  13. “Experiments reveal ‘instability threshold’ of elastic-plastic material”:

    could also be interesting for meteorology, behavior of snow / ice / mixtures:

    Stiffness, toughness, flowing behavior,

    break, demolition on terrain edges …, –> avalanches : reach of snow distribution, velocities, dissemination. …

    fluid dynamics.


  14. While the title appears flippant, it is certainly a serious topic. An obsession with equilibrium conditions holds back researchers in many fields.

  15. Isn’t this also applicable in predicting the effects from a meteor impact; the size of crater, ejecta field, propagated waves, what else is there?

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