Laboratory experiments on two coalescing axisymmetric turbulent plumes in a rotating fluid

Abstract

1We 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 T f = 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 an "early time" time t m < ∼ t r = 3T f /4, the experimentally observed merging height z me agrees well with the non-rotating theoretical, where α is the entrainment "constant" of the turbulent plumes, x 0 is the separation distance between the two plume sources, F 0 is the source buoyancy flux of each plume, and z r is the distance that the plume rises in the time t r before rotational effects become significant. Therefore, rotation does not affect the initial time to merger or the initial merger height of such "close" plumes.

Anticyclonic precession of a plume in a rotating environment

“…Although none of the experimental studies mentioned in the introduction reported plume precession, experimental images from Helfrich and Battisti [, Figure 1c] and Goodman et al [, Figure 4d] clearly show the lateral deflection of the plume. Yamamoto et al [] studied the coalescing of two adjacent plumes in a rotating environment, and their experimental images (Figures 6c–6e and 8c–8e) also show plume deflection and illustrate the “braiding” of the plumes at later times—phenomena that may be attributed to precession. The fact that Fernando et al [] did not observe any precession may be due to the use of a two‐dimensional light sheet that obscured the three‐dimensional precession, or to the running times of the experiments being too short (at our lowest rotation rate one precession period exceeds 150 s).…”

“…They report that plumes with R o > 0.3 are only impacted by rotation after impinging on the tank boundary. None of these experimental studies [ Helfrich and Battisti , ; Fernando et al , ; Bush and Woods , ; Goodman et al , ; Yamamoto et al , ] reported observing plume precession. In their turbulence‐resolving simulations at R o comparable with the DwH plume, Fabregat Tomàs et al [] reported lateral deflection of the plume and onset of anticyclonic precession.…”

A turbulent convection model with an observational context for a deep-sea hydrothermal plume in a time-variable cross flow

“…Plume coalescence from multiple sources in other settings has been measured in the laboratory and/or modeled by, e.g., Kaye and Linden [] and Yamamoto et al . []. It is the coalesced plume from multiple too‐small‐to‐resolve vent chimneys that we model in this paper.…”

“…Rona et al [1991] also observed two plumes with sources separated laterally by only $3.5 m merging in a vertical distance of $8 m above the top-most chimney orifice. Plume coalescence from multiple sources in other settings has been measured in the laboratory and/or modeled by, e.g., Kaye and Linden [2004] and Yamamoto et al [2011]. It is the coalesced plume from multiple too-small-to-resolve vent chimneys that we model in this paper.…”

Convective plumes in rotating systems

“…Although several studies have addressed the question of the baroclinic vortex, fewer studies have focused on the shape of the plume between the source and the intrusion level, and the dynamical effect of the cyclone at the base of the plume (Julien et al 1999;Yamamoto, Cenedese & Caulfield 2011). In fact, in the case of pure jets, the presence of swirl strongly affects the dynamics and creates new patterns of turbulence (Liang & Maxworthy 2005).…”