A team from Lehigh University in Pennsylvania would beg to differ, using the egg-based condiment to improve their understanding of the physics behind nuclear fusion. Although it initially sounds about as likely as using ketchup as an automotive lubricant, or mustard as a stem cell scaffold, they say the research could be one step towards turning the promise of fusion energy into reality.
Replicating the Sun’s extreme conditions to provide nearly limitless clean energy is an incredibly complex challenge. Researchers across engineering are examining the problem from a multitude of perspectives – and for Professor Arindam Banerjee and his team, that means taking advantage of the sauce’s physical properties.
Searching for solutions
The new work follows earlier research by the team, which examined hydrodynamic instabilities in fusion. “We’re still working on the same problem, which is the structural integrity of fusion capsules used in inertial confinement fusion, and Hellmann’s Real Mayonnaise is still helping us in the search for solutions,” said Professor Banerjee.
Inertial confinement fusion is a process that initiates nuclear fusion reactions by rapidly compressing and heating capsules filled with fuel – in this case, isotopes of hydrogen. When subjected to extreme temperatures and pressure, the capsules melt and form plasma.
“At those extremes, you’re talking about millions of degrees Kelvin and gigapascals of pressure, as you’re trying to simulate conditions in the Sun,” said Professor Banerjee. “One of the main problems associated with this process is that the plasma state forms these hydrodynamic instabilities, which can reduce the energy yield.”
In their first paper on the topic in 2019, Professor Banerjee and his team examined that problem, known as Rayleigh-Taylor instability. The condition occurs between materials of different densities when the density and pressure gradients are in opposite directions, creating an unstable stratification.
“We use mayonnaise because it behaves like a solid, but when subjected to a pressure gradient, it starts to flow,” he said. Using the condiment also negates the need for high temperatures and pressure conditions, which are extremely difficult to control.
Professor Banerjee’s team used a custom-built rotating wheel facility to mimic the flow conditions of plasma. Once the acceleration crossed a critical value, the condiment started to flow.
That initial research found that before the flow became unstable, the mayonnaise went through different phases. “As with a traditional molten metal, if you put a stress on mayonnaise, it will start to deform. But if you remove the stress, it goes back to its original shape,” said Professor Banerjee. “There’s an elastic phase followed by a stable plastic phase. The next phase is when it starts flowing, and that’s where the instability kicks in.”
Understanding this transition between the elastic phase and the stable plastic phase is critical, he said, because knowing when the plastic deformation starts might tell researchers before instability occurs. Engineers could then control the condition to stay within the elastic or stable plastic phase.
Elastic recovery
In their latest paper, published in Physical Review E, the team looked at criteria including material properties and the acceleration rate of the materials that undergo Rayleigh-Taylor instability.
“We investigated the transition criteria between the phases of Rayleigh-Taylor instability,” said first author Aren Boyaci. “We found the conditions under which the elastic recovery was possible, and how it could be maximised to delay or completely suppress the instability.”
The finding is important because it could inform the design of capsules in such a way that they never become unstable, the researchers said. There is nonetheless a “looming question” of how the data will fit into what happens in actual fusion capsules, the property values of which are orders of magnitude different from the soft solids used in the experiments.
“In this paper, we have nondimensionalised our data with the hope that the behaviour we are predicting transcends these few orders of magnitude,” said Professor Banerjee. “We’re trying to enhance the predictability of what would happen with those molten, high-temperature, high-pressure plasma capsules with these analogue experiments of using mayonnaise in a rotating wheel.”
Ultimately, the team is part of a global effort to turn the promise of fusion energy into reality. “We’re another cog in this giant wheel of researchers,” he said. “And we’re all working towards making inertial fusion cheaper and therefore, attainable.”
If mayonnaise could play an important part in making fusion energy reality, perhaps even its biggest haters might give it a second chance.
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