EAGER: Time-Resolved Measurements and Control of Vortex Breakdown via Heat Addition

这个项目的灵感来自于对蓝色漩涡的发现和正在进行的研究，蓝色漩涡是火焰漩涡的一种明显的崩溃模式，在这种模式下，它出人意料地转变为一个看起来温和的小蓝色火焰。蓝色漩涡不会产生任何烟尘和最低限度的污染物，这意味着最佳燃烧和潜在的清洁能源。在不经过火焰漩涡状态的情况下创建蓝色漩涡将实现安全和清洁的碳氢化合物燃烧形式，该燃烧形式可用于燃烧室、用于推进或用于受控燃烧(例如，清理漏油)。更广泛地说，由于涡旋破裂广泛存在于各种应用中，更好地了解和控制和预测其动力学对于受这种不稳定性影响的许多流体动力学系统具有广泛的意义。控制涡流破裂将使从小型微型飞行器到大型风力涡轮机的机翼和叶片产生更大的动力并增强气动稳定性，以及在冷却和紧急操作中更强劲的泵操作。本项目的目的是描述和量化不可压缩无反应流动中的涡旋破裂过程，并通过一种新型的实验来确定控制涡流破裂的机制，在这种新型实验中，能量(以热的形式)被引入涡流的核心。本项目的目的是在实验上演示热注入对非反应性不可压缩流动中涡旋破裂的影响，并评估加热率对流动破裂过程和最终状态有显著影响的参数空间。一种新型的涡旋破裂实验将被开发出来，以便能够在具有可变温度(从而密度)梯度的旋流中进行时间分辨速度场测量。互补的数值模拟(由X.Zhang和E.Oran合作者执行)将为实验设施和测试矩阵的开发提供指导，并将使探索在实验室中不易实现的参数空间区域成为可能。这些实验的结果将包括在有和没有热注入的情况下，对涡旋破裂过程中流动结构变化的定量时间分辨测量。拟议的实验有望为旋涡破裂的过程和机制提供新的物理见解，为理论和比例定律提供信息，允许将这里获得的结果推广到新的旋涡控制方法。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project was inspired by the discovery and ongoing study of the blue whirl, an apparent breakdown mode of a fire whirl in which it unexpectedly transitions to a small and seemingly benign blue flame. The blue whirl produces no soot and minimal pollutants, suggesting optimal burning and a potential source of clean energy. Creating a blue whirl without having to pass through the fire whirl state would enable a safe and clean form of hydrocarbon combustion that could be used in combustors, for propulsion, or for controlled burns (e.g., oil spill clean-up). More broadly, because vortex breakdown occurs in a wide variety of applications, a better understanding and ability to control and predict its dynamics has broad implications for many fluid dynamics systems affected by this instability. Controlling vortex breakdown would enable higher force production and enhance aerodynamic stability on wings and blades ranging from small-scale micro air vehicles to large-scale wind turbines, as well as more robust pump operation in cooling and emergency operations. This project aims to characterize and quantify the process of vortex breakdown in an incompressible non-reacting flow, and to identify mechanisms by which breakdown might be controlled via a new type of experiment wherein energy (in the form of heat) is introduced into the core of a vortex flow. The objective of this project is to experimentally demonstrate the effect of heat injection on vortex breakdown in a non-reacting incompressible flow, and to evaluate the parameter space over which heat addition has a measurable effect on the breakdown process and final state of the flow. A new type of vortex breakdown experiment will be developed to enable time-resolved velocity field measurements in a swirling flow with variable temperature (and thereby density) gradients. Complementary numerical simulations (performed by collaborators X. Zhang and E. Oran) will provide guidance in the development of the experimental facility and test matrix, and will make it possible to explore regions of the parameter space not easily achieved in the laboratory. Results from these experiments will include quantitative time-resolved measurements of the changes in flow structure during the process of vortex breakdown, with and without heat injection. The proposed experiments are expected to provide new physical insight into the process and mechanisms of vortex breakdown to inform theories and scaling laws, allowing for a generalization of the results gained here towards new methods of vortex control.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.