Hostname: page-component-78c5997874-ndw9j Total loading time: 0 Render date: 2024-11-05T19:43:14.796Z Has data issue: false hasContentIssue false
  • English
  • Français

Salt finger fluxes in a laminar shear flow

Published online by Cambridge University Press:  28 June 2010

ALEXANDRE M. FERNANDES  and
R. KRISHNAMURTI
ALEXANDRE M. FERNANDES*
Affiliation:
Department of Oceanography and Geophysical Fluid Dynamics Institute, Florida State University, Tallahassee, FL 32306, USA Departamento de Oceanografia Física, Universidade do Estado do Rio de Janeiro, R. São Francisco Xavier, 524, Sala 4017E, Rio de Janeiro, RJ 20550-900, Brazil
R. KRISHNAMURTI
Affiliation:
Department of Oceanography and Geophysical Fluid Dynamics Institute, Florida State University, Tallahassee, FL 32306, USA
*
†Email address for correspondence: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

Subtropical ocean waters are susceptible to the occurrence of salt finger instability. The effect of salt fingers in modifying water mass properties may depend upon the ubiquitous presence of oceanic shear produced by internal wave motion. We present an experimental study of the buoyancy fluxes produced by sugar–salt fingers in the presence of a laminar shear flow. As is commonly done in the laboratory, sugar (the slower diffuser) was used as a proxy for salt, and salt (the faster diffuser compared to sugar) was used as a proxy for cold. Sugar–salt fingers, initially aligned vertically, were observed to tilt when a shear flow was imposed. A consistent decrease in the salt fluxes was measured as the Reynolds number (Re) was increased by increasing the shear velocity magnitude. Through regression analysis, the salt fluxes were found to depend upon the Reynolds number as Re−0.025, Re−0.1 and Re−0.34, for density ratio values (Rρ) equal to 1.2, 1.54 and 2.1 respectively. The salt fluxes produced by the sheared fingers were also found to decrease by one order of magnitude when Rρ increased from 1.2 to 2.1. A computation of the salt Nusselt number revealed that the finger fluxes approach molecular flux values when Rρ = 2.1 and Re ≃ 140.

JFM classification

Low-Reynolds-number flows: Low-Reynolds-number flows Flow Control: Mixing enhancement
Type
Papers
Information
Journal of Fluid Mechanics , Volume 658 , 10 September 2010 , pp. 148 - 165
Copyright
Copyright © Cambridge University Press 2010

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Busse, F. H. & Whitehead, J. A. 1971 Instabilities of convection rolls in a high Prandtl number fluid. J. Fluid Mech. 47, 305–320.CrossRefGoogle Scholar
Christensen, K. T., Soloff, S. M. & Adrian, R. J. 2000 PIV sleuth: integrated particle image velocimetry (PIV) interrogation/validation software. Tech. Rep. 943. Department of Theoretical and Applied Mechanics, University of Illinois at Urbana–Champaign.Google Scholar
Dougherty, R. C. 2001 Density of salt solutions: effect on ions on the apparent density of water. J. Phys. Chem. 105, 4514–4519.Google Scholar
Gregg, M. C. & Sanford, T. B. 1987 Shear and turbulence in thermohaline staircases. Deep-Sea Res. 34, 1689–1696.CrossRefGoogle Scholar
Howard, L. N. & Veronis, G. 1987 The salt-finger zone. J. Fluid Mech. 183, 1–23.Google Scholar
Kimura, S. & Smyth, W. D. 2007 Direct numerical simulation of salt sheets and turbulence in a double-diffusive shear layer. Geophys. Res. Lett. 34, L21610.CrossRefGoogle Scholar
Krishnamurti, R. 2003 Double-diffusive transport in laboratory thermohaline staircases. J. Fluid Mech. 483, 287–314.CrossRefGoogle Scholar
Krishnamurti, R. & Howard, L. N. 1981 Large-scale flow generation in turbulence convection. Proc. Natl Acad. Sci. 78, 1981–1985.CrossRefGoogle ScholarPubMed
Krishnamurti, R. & Zhu, Y. 1996 Heat and momentum transport in sheared Rayleigh–Bénard convection. Physica D 97, 126–132.CrossRefGoogle Scholar
Kunze, E. 1990 The evolution of salt fingers in inertial wave shear. J. Mar. Res. 48, 471–504.Google Scholar
Kunze, E., Williams, A. J. III, & Schmitt, R. W. 1987 Optical microstructure in the thermohaline staircase east of Barbados. Deep-Sea Res. 34, 1697–1704.CrossRefGoogle Scholar
Linden, P. F. 1973 On the structure of salt fingers. Deep-Sea Res. 20, 325–340.Google Scholar
Linden, P. F. 1974 Salt fingers in a steady shear flow. Geophys. Fluid Dyn. 20, 325–340.Google Scholar
Ruddick, B. R. & Shirtcliffe, T. G. L. 1979 Data for double diffusers: physical properties of aqueous salt-sugar solutions. Deep-Sea Res. 26 A, 775–787.CrossRefGoogle Scholar
Schmitt, R. W. 2003 Observational and laboratory insights into salt finger convection. Prog. Oceanogr. 56, 419–433.CrossRefGoogle Scholar
Stern, M. E. 1960 The ‘salt fountain’ and thermohaline convection. Tellus 12, 172–175.Google Scholar
St Laurent, L. & Schmitt, R. W. 1999 The contribution of salt fingers to vertical mixing in the North Atlantic tracer release experiment. J. Phys. Oceanogr. 29, 1404–1424.2.0.CO;2>CrossRefGoogle Scholar
Turner, J. S. 1967 Salt fingers across a density interface. Deep-Sea Res. 14, 599–611.Google Scholar
Wells, M. G., Griffiths, R. G. & Turner, J. S. 2001 Generation of density fine structure by salt fingers in a spatially periodic shear. J. Geophys. Res. 106, 7027–7037.Google Scholar