Woods Hole Oceanographic Institution

Claudia Cenedese

»Downwelling in Basins Subject to Buoyancy Loss
»Entrainment and mixing dynamics of surface-stress-driven stratifi ed flow in a cylinder
»Laboratory experiments on two coalescing axisymmetric turbulent plumes in a rotating fluid
»Impact of fjord dynamics and glacial runoff on the circulation near Helheim Glacier
»The relationship between flux coefficient and entrainment ratio in density currents
»A new parameterization for entrainment in overflows
»Laboratory experiments on the interaction of a buoyant coastal current with a canyon: application to the East Greenland Current
»Variations in ocean surface temperature due to near surface flow: straining the cool skin layer
»Mixing in a density-driven current flowing down a slope in a rotating fluid
»Laboratory experiments on mesoscale vortices colliding with an island chain
»Laboratory observations of enhanced entrainment in dense overflows in the presence of submarine canyons and ridges
»How entraining density currents influence the stratification in a one-dimensional ocean basin
»Laboratory experiments on eddy generation by a buoyant coastal current flowing over variable bathymetry
»Laboratory experiments on mesoscale vortices interacting with two islands
»Variability of Antarctic bottom water flow into the North Atlantic
»Laboratory experiments on a mesoscale vortex colliding with topography of varying geometry in a rotating fluid
»A laboratory model of thermocline depth and exchange fluxes across circumpolar fronts
»A dense current flowing down a sloping bottom in a rotating fluid
»Laboratory experiments on mesoscale vortices colliding with a seamount
»Stability of a buoyancy-driven coastal current at the shelf break
»Eddy-shedding from a boundary current around a cape over a sloping bottom
»Cyclone and anticyclone asymmetry in a rotating stratified fluid over bottom topography

Yamamoto H., Cenedese C. and Caulfield C.P., Laboratory experiments on two coalescing axisymmetric turbulent plumes in a rotating fluid, Physics of Fluids, 23, 056601, 2011

We investigate the early-time coalescence of two co-flowing axisymmetric turbulent plumes and the later-time flow of the induced vortices in a rotating, homogeneous fluid using laboratory experiments. The experiments demonstrate the critical importance of the rotation period Tf = 2π/f, where f is the Coriolis parameter of the background rotation. We find that if the plumes’ sources are sufficiently “close” for the plumes to merge initially at a time tm ≤ tr = 3Tf/4, the experimentally observed merging height zme agrees well with the non-rotating theoretical relationship of zmt ≈ (0.44/α )x0 < zr = 5.5 F01/4 f −3/4, where α is the entrainment “constant” of the turbulent plumes, x0 is the separation distance between the two plume sources, F0 is the source buoyancy flux of each plume, and zr is the distance that the plume rises in the time tr before rotational effects become significant. Therefore, rotation does not affect the initial time to merger or the initial merger height of such “close” plumes. For “late” times t > tr, however, the flow dynamics are substantially more complicated, as the flow becomes significantly affected by rotation. The propagation and entrainment of the plumes becomes strongly affected by the vortices induced by the entrainment flow in a rotating environment. Also, the plume fluid itself starts to interact with these vortices. If the plumes have already initially merged by this time t = tr, a single vortex (initially located at the midpoint of the line connecting the two plume sources) develops, which both advects and modifies the geometry of the merging plumes. Coupled with the various suppressing effects of rotation on the radial plume entrainment, the “apparent” observed height of merger can vary substantially from its initial value. Conversely, for more widely separated “distant” plumes, where x0 > xc = (25 α/2)F01/4f −3/4, the plumes do not merge before the critical time tr when rotation becomes significant in the flow dynamics and two vortices are observed, each located over a plume source. The combined effect of these vortices with the associated suppression of entrainment by rotation thus significantly delays the merger of the two plumes, which apparently becomes possible only through the merger of the induced vortices.

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