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A search for vortex rings in liquid helium Chapman, David Spencer

Abstract

While endeavouring to produce macroscopic vortex rings in liquid helium by a drop method, a general study of the formation of vortex rings when a liquid drop falls into a stationary bath of the same liquid was made. Preliminary investigations were made using room temperature liquids with a wide range of surface tensions, densities and viscosities. A cryostat was designed to study vortex ring formation in liquid nitrogen, liquid helium I, and liquid helium II. A numerical method, involving vorticity and Stokes stream function as parameters, for the solution of non-steady, rotational, viscous flows is outlined. Experimental results confirm the reported existence of optimum dropping heights from which the drop develops into a superior vortex ring. These optimum heights are analysed, by a photographic study, in terms of the liquid drop oscillation. It is found that optimum vortex rings are formed, if the drop is spherical at the moment of contact with the bath, and is changing from an oblate spheroid to a prolate spheroid. Vortex rings were detected in liquid nitrogen but not in liquid helium.

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