Researchers Resolve Turbulent Flow Paradox with New Setup

Researchers at the Okinawa Institute of Science and Technology (OIST) have successfully addressed a long-standing contradiction in the study of rotating turbulence. Their findings, published on November 5, 2025, in the journal Science Advances, confirm that Kolmogorov’s theoretical framework for turbulence universally applies to small-scale turbulent flows in Taylor-Couette (TC) setups, contrary to previous beliefs.

Turbulent flows, which can be observed in everyday activities like stirring coffee or in powerful natural phenomena such as typhoons, have perplexed scientists for decades. The challenge lies in accurately describing and predicting these flows, which have significant implications for various fields including meteorology and astrophysics. Two pivotal formulations in turbulence research are Kolmogorov’s framework, which describes how energy dissipates through various scales, and TC flows, known for their complex turbulent behaviors.

Long-standing Contradiction Addressed

Despite extensive experimental research, Kolmogorov’s principles appeared not to apply to TC flows, leading to a major inconsistency in fluid dynamics. Professor Pinaki Chakraborty, who heads the Fluid Mechanics Unit at OIST, highlighted that this discrepancy had troubled the field for years. “The problem has long stood out like a sore thumb,” he stated. “With this discrepancy solved, we have set a new baseline for studying these complex flows.”

TC flows are generated within a confined space between two independently rotating cylinders. These flows are relatively simple to create but exhibit a variety of turbulent behaviors, including the formation of rotating vortices known as Taylor rolls. Such phenomena have contributed significantly to the development of fluid dynamics as a scientific discipline.

Kolmogorov’s influential work in 1941 introduced an idealized energy cascade model. He proposed that stirring a body of water creates a large vortex which then breaks down into progressively smaller eddies until dissipating as heat. This model, known as the -5/3rd law, has been found to apply universally across many turbulent flows. Yet, TC flows consistently eluded this framework, presenting a significant challenge to researchers.

Innovative Experimental Setup Unlocks New Insights

Over the course of nine years, OIST researchers built a cutting-edge TC setup capable of producing turbulent flows with Reynolds numbers reaching up to 10^6, one of the highest in the world. The engineering involved required accommodating precise sensors within a rapidly spinning cylinder, all while maintaining a controlled temperature environment.

Initial analyses using Kolmogorov’s traditional approach revealed that the -5/3rd law did not fit the data from their experiments. This prompted the research team, led by first author Julio Barros, to broaden their analysis. They shifted focus from the inertial range to include the complete spectrum of small-scale flows, aiming to incorporate dissipative effects into their calculations.

By applying this broader perspective, the team discovered that the energy spectra measured from their setup converged on a universal curve, confirming Kolmogorov’s predictions. “Rescaling the measurements by the general theory yielded the universality that Kolmogorov predicted,” Barros noted. “The framework holds.” This breakthrough not only resolves a critical inconsistency in the field but also enhances the potential of TC flows for future research in fluid mechanics.

Professor Chakraborty emphasized the advantages of TC setups, stating, “The beauty of TC flow setups is that they are closed systems. No pumps, no obstructions in the flow. We can study the flow of whatever liquid and additive that we desire.” This newfound understanding paves the way for innovative applications in theoretical and applied fluid dynamics.

Overall, the resolution of this paradox marks a significant advancement in the understanding of turbulent flows, with implications that extend across various scientific disciplines. The research team at OIST has set a solid foundation for future studies, enabling a deeper exploration of the complexities inherent in fluid mechanics.