Exploring Flow Structures in a 2D Fluid

该项目涉及流体湍流，这是一个长期存在的重大问题，在很大程度上仍未得到解决。一个主要的困难是存在大量在流体中强烈相互作用的自由度。这项拟议的研究试图通过研究二维几何中的湍流来简化问题，在二维几何中，可以使用快速视频成像系统长时间跟踪每个流体元素的运动。二维流体运动是在几微米厚的自由悬浮薄液膜中，在电磁场的驱动下实现的。研究的重点将集中在流体动力相关结构的相互作用和稳定性，如流动中的涡旋和鞍点。这些相干结构被认为是湍流中能量和角动量转移的原因。实验结果将与对二维湍流中的旋涡和鞍形分布进行定量预测的统计模型进行比较。随着对二维湍流行为的更好理解，这项研究可以为更困难的三维湍流问题提供新的线索，这不仅与物理有关，而且与工程和气象学有关。这项研究将涉及研究生和本科生，在一个动态的环境中，研究和教育齐头并进。参与这项研究的学生使用最先进的设备来研究一个引人入胜和相关的基本物理系统，为未来的挑战和学术、工业和政府工作人员做好准备。流体湍流是一个复杂的现象，影响到科学和工程的各个领域。这种现象的复杂性最好地反映在我们预测财富模式的能力有限上，尽管近年来计算能力有了显著提高。这项工作旨在理解二维空间中的湍流，其中的复杂性显著降低，但仍然保留了三维湍流最重要的成分，即强相互作用和非确定性。为了实现二维流动，使用了一种厚度约为几微米的自由悬浮液膜，并由电磁场驱动。使用最先进的视频成像系统，将在较长的一段时间内跟踪每个流体元素在胶片中的湍流演变。研究的重点是了解流体动力涡如何相互作用，以及它们在不同流动条件下的稳定性。新的洞察将有助于我们理解更困难的三维湍流现象。流动的液膜不仅对科学研究有价值，而且是各级物理教学的绝佳实验室。参与这项工作的学生、毕业生和本科生将接受基础科学(物理)、现代成像处理技术和计算机编程方面的严格培训。这使他们在未来的学术界、工业界或政府的职业生涯中得到了全面的发展。

The project deals with fluid turbulence, a significant, long-standing problem that remains largely unsolved. A major difficulty is the presence of a large number of degrees of freedom that are strongly interacting in a fluid. The proposed research attempts to simplify the problem by studying turbulence in a two-dimensional geometry in which motion of each fluid element can be followed over a long period of time using a fast video imaging system. Two-dimensional fluid motion is realized in a freely suspended thin liquid film, a few microns thick, and driven by an electromagnetic field. The research will focus on interaction and stability of hydrodynamic coherent structures, such as vortices and saddle points in the flow. It is believed that these coherent structures are responsible for energy and angular momentum transfer in turbulence. The experimental results will be compared with statistical models that make quantitative predictions about distributions of vortices and saddles in two-dimensional turbulence. With a better understanding of how two-dimensional turbulence behaves, the research can shed new light on more difficult problems of three-dimensional turbulence, which is relevant not only to physics but also to engineering and meteorology. The research will involve both graduate and undergraduate students in a dynamic environment where research and education go hand in hand. The students participating in this research use state-of-the-art equipment to study a fundamental physical system that is fascinating and relevant, preparing them for future challenges, and for the academic, industry, and government workforce.Fluid turbulence is a complex phenomenon, affecting all sections of science and engineering. The complexity of the phenomenon is best reflected in our limited ability to predict wealth patterns, despite dramatic improvements in the computational power in recent years. This work is aimed at understanding turbulence in a two-dimensional space, where the complexity is significantly reduced but yet still retains the most important ingredients of three-dimensional turbulence, i.e., strong interaction and non-determinism. To achieve two-dimensional flow, a thin freely suspended liquid film, about a few microns in thickness, is used and is driven by an electromagnetic field. Using a state-of-the-art video imaging system, the evolution of turbulence in the film will be followed for each fluid element for an extended period of time. The focus of the research is to understand how hydrodynamic vortices interact with each other and how stable they are under different flow conditions. The newly gained insight would help us to understand more difficult three-dimensional turbulent phenomenon. A flowing liquid film is not only valuable for scientific research; it is also a wonderful laboratory for teaching physics at all levels. Students, graduates and undergraduates who participate in this work, will receive rigorous training in fundamental science (physics), modern imaging processing techniques, and computer programming. This makes them well rounded for a future career in academe, industry or government.