From the start of the project to its conclusion, the work focused on establishing the experimental, theoretical, and computational foundations needed to investigate non-equilibrium turbulence. The project has in essence successfully completed all planned activities.
A major achievement was the creation of a new world-leading laboratory for fundamental turbulence research. The project designed and built flow-generation facilities capable of producing turbulent flows with controllable levels of non-equilibrium, and developed advanced laser-based measurement techniques required to study both the smallest and the largest relevant flow scales. Two extensive experimental campaigns were completed: one resolved the tiny dissipative scales to quantify departures from equilibrium, and one captured the global turbulence dynamics in time and all three spatial dimensions. These campaigns required significant innovation in laser diagnostics, data acquisition, and big-data handling, all of which now operate at a mature and reliable level.
In parallel, a suite of fully resolved Direct Numerical Simulations was carried out early in the project. These simulations, which compute all relevant turbulent scales directly from the governing equations, were essential for developing the theoretical framework, guiding the analysis methods, and informing the design of the experimental facilities. Their successful execution required substantial computational resources and storage capacity.
A central scientific contribution of the project is the development of a new theoretical framework for analyzing turbulence under non-equilibrium conditions. By revisiting and extending classical mathematical formulations, the project produced tools capable of describing more complex and realistic turbulent flows than those assumed in traditional equilibrium theory. Using this framework, it was possible to quantify the degree of non-equilibrium and to characterize how energy is exchanged between turbulent scales when the flow is accelerated or otherwise perturbed. Notably, the analysis revealed that even flows traditionally considered “equilibrium turbulence” exhibit subtle non-equilibrium dynamical features.
The results have been disseminated widely through invited and contributed presentations at international conferences and workshops, as well as through journal publications. The project’s scientific advances have also been consolidated in the PI’s Doctor Technices dissertation, a thesis-based degree awarded in Denmark to recognize exceptional scientific achievement and significant contributions to engineering and technological science.
Overall, the project delivered a unique combination of new experimental infrastructure, advanced theoretical tools, and high-fidelity computational data. Together, these outcomes provide a solid foundation for future turbulence modeling efforts and will facilitate continued exploitation of the results by the broader research community.
