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Full-Text Articles in Physics

Retention Of Rising Oil Droplets In Density Stratification, Tracy L. Mandel, De Zhen Zhou, Lindsay Waldrop, Maxime Theillard, Dustin Kleckner, Shilpa Khatri Dec 2020

Retention Of Rising Oil Droplets In Density Stratification, Tracy L. Mandel, De Zhen Zhou, Lindsay Waldrop, Maxime Theillard, Dustin Kleckner, Shilpa Khatri

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

In this study, we present results from experiments on the retention of single oil droplets rising through a two-layer density stratification, with the goal of quantifying and parametrizing the impact of stratification on timescales that describe the delay in rising. These experiments confirm the significant slowdown observed in past literature of settling and rising particles and droplets in stratification, and these are the first experiments to study single liquid droplets as opposed to solid particles or bubbles. By tracking the motion of the droplets as they rise through a stratified fluid, we identify two new timescales which quantitatively describe this …


Generalized Helicity And Beltrami Fields, Roman V. Buniy, Thomas W. Kephart May 2014

Generalized Helicity And Beltrami Fields, Roman V. Buniy, Thomas W. Kephart

Mathematics, Physics, and Computer Science Faculty Articles and Research

We propose covariant and non-abelian generalizations of the magnetic helicity and Beltrami equation. The gauge invariance, variational principle, conserved current, energy-momentum tensor and choice of boundary conditions elucidate the subject. In particular, we prove that any extremal of the Yang-Mills action functional 1/4 f(Omega) trF(mu nu) F-mu nu d(4)x subject to the local constraint epsilon(mu nu alpha beta)trF(mu nu)F(alpha beta) = 0 satisfies the covariant non-abelian Beltrami equation.