title: Inertially driven buckling and overturning of jets in a Hele-Shaw cell.
abstract: We study a fluid jet descending through stratified surroundings at low Reynolds number in Hele-Shaw flow. The jet buckles and overturns inside a conduit of entrained fluid which supports smooth or unstable traveling waves. A model of the recirculating flow within the conduit shows that buckling and waves arise from Kelvin-Helmholtz instabilities and quantitatively accounts for the main experimental observations. Beyond the onset of the instability, a damped, forced Burgers' equation obtained from corrections to Darcy's law for small Reynolds number governs the interface dynamics and supports singularities corresponding to the observed jet overturning and unstable waves.
authors.affiliation: Department of Physics and Program in Applied Mathematics, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Adriana I
authors.initials: AI
authors.lastname: Pesci
authors.forename: Martin A
authors.initials: MA
authors.lastname: Porter
authors.forename: Raymond E
authors.initials: RE
authors.lastname: Goldstein