In flows 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). Our focus is on understanding the catastrophic transition from laminar to turbulent states in contained rotating flows. While there is abundant experimental evidence for this phenomenon, no consensus exists as to the underlying physical mechanism. The two dominant paradigms are that the transition arises either from resonance of inviscid modes or directly as an instability of the basic state. We will resolve this dichotomy using theoretical, numerical and experimental studies of transition in precessing rotating flows (where the driving mechanism is temporal variation of the rotation vector) and in flows that generate large inertial wave responses through interaction of oscillatory Stokes layers with background rotation (rotation vector is fixed). Using direct numerical simulation and linear stability analysis, together with experimental measurements from international collaborators, we will be able to precisely identify the mechanisms responsible for catastrophic transition. intellectual merit of this proposal This project will enable breakthroughs in our understanding of the mechanisms responsible for the catastrophic transition to turbulence in confined rapidly rotating flows. This is a fundamental issue that has intrigued researchers for nearly 50 years, and has many potentially important applications. Our methods will be firmly based in direct numerical simulation and stability analysis of viscous flows where we can access all the dynamics, and we will directly match these to experiments. broader impacts of this proposal This project includes the 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.
|Effective start/end date||9/1/13 → 8/31/17|
- National Science Foundation (NSF): $353,470.00