Studies of Liquid Interface Dynamics Using a Highly Characterized System

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9801844 Maynard This is a low temperature physics research project that makes use of liquid helium, a highly characterized quantum liquid. Innovative acoustic and optical techniques are used to study liquid interface (surface) dynamics, including liquid coalescence, bubble entrainment, droplet impact, and similar phenomena. The experiments are designed to test or extend theories of the behavior of liquid surfaces currently being developed in condensed matter physics. The main focus is on fluid droplet impact and the mechanisms of entrainment gases in the mode believed responsible for generation of underwater noise. While most existing measurements and theoretical models have been for water, the proposed experiments will make use of liquid helium, whose high purity and ability to be precisely and accurately controlled over a wide range of parameters make in uniquely suited for quantitatively testing current fluid dynamics theories. Drops will be made to collide with the bulk liquid interface, and the rapidly changing stress field occurring at the interface rupture will radiate sound waves which will be detected with a temporal resolution of 10 ns, approaching rupture time scales at the molecular level. The research program will provide unique training opportunities for graduate students in methods of acoustics, an area often overlooked in contemporary physics, and involving special, often-subtle experimental methods. This is a fundamental project but the results are potentially relevant to a range of practical situations including industrial processes involving foams and emulsions, in commercial blenders and sprayers, application of ultrasound in medicine, generation of underwater noise by rain, which is important in military and environmental monitoring, etc. %%% This is a low temperature physics research project that makes use of liquid helium, a highly characterized quantum liquid. Innovative acoustic and optical techniques are used to study liquid interface (surface) dynamics, including liquid coalescence, bubble entrainment, droplet impact, and similar phenomena. The experiments are designed to test or extend theories of the behavior of liquid surfaces currently being developed in condensed matter physics. The main focus is on fluid droplet impact and the mechanisms of entrainment gases in the mode believed responsible for generation of underwater noise. While most existing measurements and theoretical models have been for water, the proposed experiments will make use of liquid helium, whose high purity and ability to be precisely and accurately controlled over a wide range of parameters make in uniquely suited for quantitatively testing current fluid dynamics theories. Drops will be made to collide with the bulk liquid interface, and the rapidly changing stress field occurring at the interface rupture will radiate sound waves which will be detected with a temporal resolution of 10 ns, approaching rupture time scales at the molecular level. The research program will provide unique training opportunities for graduate students in methods of acoustics, an area often overlooked in contemporary physics, and involving special, often-subtle experimental methods. This is a fundamental project but the results are potentially relevant to a range of practical situations including industrial processes involving foams and emulsions, in commercial blenders and sprayers, application of ultrasound in medicine, generation of underwater noise by rain, which is important in military and environmental monitoring, etc. ***