Double-diffusive convection

Liang Y. (1994) Axisymmetric double-diffusive convection in a cylindrical container linear stability analysis with applications to molten Ga0-Al203-Si02. In Double-... 

Below the main pycnocline, one finds the layer that is named sometimes generally as the deep layer. The present-day concepts about the vertical structure of its upper part have already been considered (see Fig. 2b). Below the intermediate isothermal layer, in the depth range from 700 to 1700 m, one observes a layer with a slow increase in the temperature and salinity with depth sometimes broken by T,S inversions with vertical scales about 10 m, which is typical of the fine T,S structure of the waters [11] (Fig. 3b). Theoretical estimates [13] show that they may result from the thermal type of double diffusion (layered convection), which is the principal mechanism of the vertical heat and salt exchange in this layer. 

Ozsoy E, Top Z, White G, Murray JW (1991) Double diffusive intrusions, mixing and deep sea convection processes in the Black Sea. In Izdar E, Murray JW (eds) The Black Sea oceanography. NATO/ASI series. Kluwer Academic, Dordrecht, p 17... 

The existence of the Black Sea bottom convective layer (BCL) has important implications for the physical and chemical exchange at the sediment/water interface and at the interface between intermediate and bottom water masses. Two-fold increased vertical gradients of dissolved sulphide at the upper boundary of the BCL suggest the presence of the anoxic interface separating entire anoxic water mass dominated by turbulent diffusion from underlying waters of the BCL where double diffusion is the main mixing mechanism. 

Schmitt R. W. (1998) Double-diffusive convection. In Ocean Modelling and Parametrization (eds. E. P. Chassignet and J. Verron). Kluwer, Amsterdam, pp. 215-234. 

Thermal SN explosion mechanism was proposed by Colgate and White [32], In this picture, part of the neutrino flux liberated in the core collapse is deposited to the stellar mantle to make it unbound ( 1051 ergs is needed). Specific mechanisms include neutrino-driven fluid instabilities, for example convection both above neutrinosphere and inside the proto-NS. Neutrino-driven convection, however, may not be as important as thought before, as follows from recent detailed 2D studies of convection [24], Instead, other fluid instabilities such as newly found double-diffusive instability (the so-called lepto-entropy fingers ) [23], may effectively increase neutrino luminosity to help successful explosion. Note here that process ve -I u(, e1 I e —>7 + 7... 

For arbitrary values of Ra and Ra, the principle of exchange of stabilities does not hold. We therefore limit our analysis to the case of two free surfaces, for which we can obtain closed-form analytic results. Although idealistic, this case is adequate to demonstrate the most important qualitative features of the double-diffusive convection problem. 

Figure 12-6. A sketch of the stability diagram for double-diffusive convection. The stability boundary is the solid line ZXW. The dashed line PQ denotes the boundary for static stability where the net density gradient is equal to zero. It is assumed in this sketch that Pr/Sc < 1.

Bischoff JL, Rosenbauer RJ (1989) Salinity variations in submarine hydrothermal systems by layered double-diffusive convection. J Geol 97 613-623... 

GRAPH 10.29 Formal Graph of a double mass transfer, the first one ensured by stationary diffusion in a homogeneous and isotropic medium, the second one ensured by convection. The diffusion path goes through a conduction step, which dissipates energy, whereas the convection one does not undertake any dissipative path. 

Figure 9.5 The mechanism of double-diffusive convection in the fingering regime. A/o and Apr are in the opposite direction, and the net density gradient appears to be stable. However, if a small parcel of the warm, salty solution enters the lower section, then because the heat diffuses faster than the salt, the parcel is left with a greater density than the surroimding...

Both of the above types of convection are categorized as double-diffusive convection ( thermohaline when the two components are heat and salt), and, more generally, multicomponent convection. It is not necessary that the two components be a solute and heat. Any two materials with different diffusivities can cause these phenomena, even if the differences are as small as with salt and sugar. This phenomenon has been extensively studied by oceanographers because of the role it plays in ocean current mixing. The two behaviors we have described correspond to the fingering and diffusive regimes of double-diffusive convection. 

Figure 9.6 The mechanism of double-diffusive convection in the diffusive regime. The parcel of hot, salty solution that enters the cold, fresh region above loses heat, becoming more dense than the surrounding region. It sinks back to the hot region and regains heat, leading to an oscillatory motion.

Pojman, J. A, Komlosi, A. Nagy, I. P. 1996c. Double-Diffusive Convection in Traveling Waves in the lodate-Sulfite System Explained, J. Phys. Chem. 100, 16209-16212. 

The role of interfacial deformation is considered in the stability analysis of fluid layers heated from below or above when there is an open interface to ambient air, and double diffusive transport of heat and solute thus leading to variations of interfacial tension that compete or cooperate with buoyancy phenomena. The onset of both oscillatory convection and steady patterns is described. 

Beckermann C, Viskanta R (1988). Double-diffusive convection during dendritic solidification of a binary mixture. PCH 10 195-213... 

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