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.
