Condiments play a crucial role in advancing research on the phases of Rayleigh-Taylor instability, providing valuable insights that could greatly influence the development of clean energy through inertial confinement fusion processes. Mayonnaise, in particular, continues to be instrumental in deepening our understanding of the complex physics involved in nuclear 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,” says Arindam Banerjee, the Paul B. Reinhold Professor of Mechanical Engineering and Mechanics at Lehigh University.
Fusion reactions are the incredible power source that fuels the sun. Scientists believe that if this process can be replicated on Earth, it could provide a nearly limitless and environmentally friendly energy source for humanity. However, recreating the extreme conditions found in the sun is an immensely complex challenge. Researchers from various scientific and engineering fields, like Banerjee and his team, are tackling this problem from multiple angles.
Inertial confinement fusion is a method that triggers nuclear fusion reactions by rapidly compressing and heating tiny capsules filled with fuel, such as isotopes of hydrogen. Under intense temperatures and pressure, these capsules liquefy and transform into plasma, the charged state of matter that has the potential to generate energy.
“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,” says 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 2019, Banerjee and his team published their first paper on the subject, examining the Rayleigh-Taylor instability, which occurs when materials of different densities experience opposing density and pressure gradients, leading to an unstable stratification.
According to Banerjee, they chose to use mayonnaise due to its behavior resembling that of a solid, but when subjected to a pressure gradient, it begins to flow. Additionally, using condiments eliminates the necessity for high temperatures and pressure conditions, which are notably difficult to manage.
Banerjee’s team utilized a unique rotating wheel facility in his Turbulent Mixing Laboratory to replicate the flow conditions of the plasma. When the acceleration exceeded a critical value, the mayo started to flow.
During their initial research, the team discovered that before the flow became unstable, the soft solid, in this case, the mayo, underwent several 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,” he says. “So 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.”
Ensuring a thorough understanding of the transition from the elastic phase to the stable plastic phase is vital. Recognizing the onset of plastic deformation could provide valuable insight into when instability might occur. By controlling the conditions to remain within the elastic or stable plastic phase, researchers can mitigate the risk of instability.
In their recent publication in Physical Review E, the team, which includes former graduate student and study first author Aren Boyaci ’24 PhD, now a Data Modeling Engineer at Rattunde AG in Berlin, Germany, examined the material properties, perturbation geometry (amplitude and wavelength), and acceleration rate of materials undergoing Rayleigh-Taylor instability.
“We investigated the transition criteria between the phases of Rayleigh-Taylor instability and examined how that affected the perturbation growth in the following phases,” Boyaci says. “We found the conditions under which the elastic recovery was possible and how it could be maximized to delay or completely suppress the instability. The experimental data we present are also the first recovery measurements in the literature.”
The discovery is significant because it could help shape the design of the capsules to prevent them from becoming unstable.
Nevertheless, there is a pressing question about how the team’s findings relate to the behavior of real fusion capsules, which have property values vastly different from those of the soft solids used in their tests.
“In this paper, we have non-dimensionalized our data with the hope that the behavior we are predicting transcends these few orders of magnitude,” says Banerjee. “We’re trying to enhance the predictability of what would happen with those molten, high-temperature, high-pressure plasma capsules with these analog experiments of using mayonnaise in a rotating wheel.”
Ultimately, Banerjee and his team are contributing to the worldwide endeavor to transform the potential of fusion energy into a tangible reality.
“We’re another cog in this giant wheel of researchers,” he says. “And we’re all working towards making inertial fusion cheaper and, therefore, attainable.”
Journal reference:
- Aren Boyaci, Arindam Banerjee. Transition to plastic regime for Rayleigh-Taylor instability in soft solids. Physical Review E, 2024; DOI: 10.1103/PhysRevE.109.055103