On the relationship between finger width, velocity, and fluxes in thermohaline convection

Sreenivas, K. R. ; Singh, O. P. ; Srinivasan, J. (2009) On the relationship between finger width, velocity, and fluxes in thermohaline convection Physics of Fluids, 21 (2). 026601_1-026601_15. ISSN 1070-6631

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Official URL: http://link.aip.org/link/doi/10.1063/1.3070527

Related URL: http://dx.doi.org/10.1063/1.3070527

Abstract

Double-diffusive finger convection occurs in many natural processes. The theories for double-diffusive phenomena that exist at present consider systems with linear stratification in temperature and salinity. The double-diffusive systems with step change in salinity and temperature are, however, not amenable to simple stability analysis. Hence factors that control the width of the finger, velocity, and fluxes in systems that have step change in temperature and salinity have not been understood so far. In this paper we provide new physical insight regarding factors that influence finger convection in two-layer double-diffusive system through two-dimensional numerical simulations. Simulations have been carried out for density stability ratios (Rρ) from 1.5 to 10. For each density stability ratio, the thermal Rayleigh number (RaT) has been systematically varied from 7×103 to 7×108. Results from these simulations show how finger width, velocity, and flux ratios in finger convection are interrelated and the influence of governing parameters such as density stability ratio and the thermal Rayleigh number. The width of the incipient fingers at the time of onset of instability has been shown to vary as RaT−⅓. Velocity in the finger varies as RaT/Rρ. Results from simulation agree with the scale analysis presented in the paper. Our results demonstrate that wide fingers have lower velocities and flux ratios compared to those in narrow fingers. This result contradicts present notions about the relation between finger width and flux ratio. A counterflow heat-exchanger analogy is used in understanding the dependence of flux ratio on finger width and velocity.

Item Type:Article
Source:Copyright of this article belongs to American Institute of Physics.
Keywords:Convection; Density; Diffusion; Flow Simulation
ID Code:79949
Deposited On:30 Jan 2012 05:16
Last Modified:30 Jan 2012 05:16

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