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Paul Miller, Peter Lindstrom, and Andrew Cook, Lawrence Livermore National Laboratory |
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This video documents a direct numerical simulation of an experiment by Niederhaus and Jacobs [Phys. Fluids 10, S6 (1998)]. The animations illustrate the behavior of two high-Schmidt-number, incompressible fluids of different densities that are initially separated by a sinusoidal interface and then impulsively accelerated. The acceleration results in the deposition, on the density interface, of baroclinic vorticity that coalesces into a single large vortex. At intermediate time, when the density interface is rolled up by this large vortex, the low-pressure region caused by the vortex interacts with the steep density gradients, producing new baroclinic vorticity. We term this secondary instability a centrifugal baroclinic instability. The video shows the experimental geometry, the simulation parameters, and a series of animations of the density, vorticity, pressure, baroclinic torque (vorticity production), and baroclinic torque colored on a height map of the pressure field. It concludes with an animated height-map depiction of the vorticity field, with a color map of the baroclinic torque superimposed. Note the opposite-signed values of baroclinic torque, including negative production (blue) high on ridges (locations of large positive vorticity). This increase in complexity of the vorticity structure eventually leads to a breakdown of the initial jelly-roll structure of the density field, producing increased amounts of mixed fluid at later times (green), as observed experimentally. Acknowledgments: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. |
