CAREER: Turbulence in a rapidly changing world

非常接近车辆表面的空气或水的流动是复杂的，并且对车辆的性能至关重要。这些“边界层”流是阻力的主要来源，特别是在机动期间，控制流的路径如何紧密地遵循车辆的几何形状，这可以显著地改变车辆所经受的力。虽然以前对大型飞行器在常风条件下的边界层流动和小型飞行器在非定常机动过程中的边界层流动已经做了大量的工作，但对大型飞行器在非定常条件下的边界层流动却做得很少。为了在阵风或波浪条件下设计和安全操纵大型飞行器，需要更多关于其边界层如何响应加速和减速的基本知识。该项目创造了新的实验能力，并利用这些能力来研究边界层加速和减速，从根本上了解由于不稳定性而导致的行为变化。这项工作将把研究结果整合到伊利诺伊大学厄巴纳-香槟分校的课程中，并将通过教育正义项目的数学辅导计划使丹维尔惩教中心的被监禁学生受益。该项目将推进加速边界层的知识和实验能力。存在关于流动加速速率的阈值，低于该阈值可以在不考虑加速的情况下预测流动，并且高于该阈值，加速定性地改变物理行为。该项目将量化阈值及其对三种配置的流动参数的依赖性。流动对加速和减速的反应不同，该项目将量化和理解这些对边界层的不同影响。最后，在加速之后，流量恢复到稳定状态;该项目将量化这种恢复的性质。总之，对阈值、滞后和恢复的理解和观察将形成对加速湍流边界层的科学理解和预测的基础。该项目还将提高研究时间加速边界层的实验能力。使用新的，可快速重构的几何形状，该项目将产生高雷诺数，非定常流动条件。科学发现将作为北约先进车辆技术工作组的一部分进行分享。该计划还支持在丹维尔惩教中心为被监禁的学生建立一个分层数学教学计划。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.