CAREER: Turbulence in a rapidly changing world

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

The flow of air or water very near the surface of vehicles is complex and is crucial to the performance of a vehicle. These "boundary layer" flows are a major source of drag and, especially during maneuvers, control how closely the flow’s path follows the geometry of the vehicle, which can dramatically change the forces that the vehicle experiences. While significant prior work has been done on boundary layer flows for large vehicles under constant wind conditions, and on boundary layer flows for very small vehicles during unsteady maneuvers, little work has been done on boundary layer flows for large vehicles under unsteady conditions. To design and safely maneuver large vehicles in gusty or wavy conditions, more fundamental knowledge is needed about how their boundary layers respond to accelerations and decelerations. This project creates new experimental capabilities and uses those capabilities to study boundary layers accelerating and decelerating to fundamentally understand changes in behavior due to unsteadiness. The work will integrate the findings into courses at the University of Illinois Urbana-Champaign and will benefit incarcerated students at the Danville Correctional Center through a math tutoring program with the Education Justice Project. The project will advance knowledge and experimental capabilities for accelerating boundary layers. There is a threshold on the rate of flow acceleration, below which the flow can be predicted without accounting for the acceleration, and above which the acceleration qualitatively changes the physical behavior. The project will quantify that threshold and its dependence on flow parameters for three configurations. The flow responds differently to accelerations and decelerations and the project will quantify and understand these different effects on the boundary layer. Finally, after an acceleration the flow recovers to a steady state; the project will quantify the nature of that recovery. Together, the understanding and observation of thresholds, hysteresis, and recovery will form a basis for scientific understanding and prediction of accelerating turbulent boundary layers. The project will also advance the state-of-the-art in experimental capabilities for studying temporally accelerating boundary layers. Using novel, rapidly reconfigurable geometries the project will generate high-Reynolds number, unsteady flow conditions. Scientific findings will be shared as part of a NATO advanced vehicle technologies working group. The program also supports the formation of a tiered math teaching program at Danville Correctional Center for incarcerated students. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.