In floows with dominant background rotation, Coriolis accelerations provide restoring forces that can act to suppress radial motion, or lead to oscillatory behavior. Such flows are found in a wide range of applications in mechanical engineering (swirl burners, rotating machines), aerospace(vortex-generated lift, fuel tanks of spin-stabilized spacecraft), minerals processing (mixing, suspension and separation), to geophysics (molten planet cores, tropical cyclones).
Intellectual Merit: The focus is on understanding the catastrophic transition from laminar to turbulent states in contained rotating flows. While there is experimental evidence for this phenomenon, no consensus exists as to the underlying physical mechanism. The two dominant interpretations are that the transition arises either from resonance of inviscid modes or directly as an instability of the basic state. The PI proposes to resolve this argument by using theoretical, numerical and experimental studies. Simulations and analysis at the PI's laboratory will be complemented with experiments conducted by international collaborators. Precessing rotating flows (where the driving mechanism is temporal variation of the rotation vector) and flows that generate large inertial wave responses through interaction of oscillatory Stokes layers with background rotation (rotation vector is fixed) will be examined. The research approach will be based in direct numerical simulation and stability analysis of viscous flows, so that all the dynamics can be studied and directly matched to experiments.
Broader Impacts: The scientific problem to be investigated is a fundamental issue that has intrigued researchers for nearly 50 years, and has many potentially important applications, as already mentioned above.
This project includes interdisciplinary training of graduate students by mentors who have decades of interdisciplinary research experience between them. Being a part of a larger international collaboration, there will be ample opportunities for exchange visits, providing a valuable training and mentoring experience for all involved. Our involvement with research experiences for undergraduates will be continued, where aspects of the flow problems will be isolated into projects suitable for undergraduates. For the broader community, all solvers developed in the project will be freely and readily available.
