scholarly journals Finger puzzles

2012 ◽  
Vol 692 ◽  
pp. 1-4 ◽  
Author(s):  
R. W. Schmitt
Keyword(s):  
Growth Rate ◽  
Finite Amplitude ◽  
Double Diffusive Convection ◽  
Magma Chambers ◽  
Fluid Systems ◽  
Salt Fingers ◽  
Diffusive Convection ◽  
Stellar Interiors ◽  
Secondary Instabilities ◽  
Double Diffusive

AbstractSalt fingers are a form of double-diffusive convection that can occur in a wide variety of fluid systems, ranging from stellar interiors and oceans to magma chambers. Their amplitude has long been difficult to quantify, and a variety of mechanisms have been proposed. Radko & Smith (J. Fluid Mech., this issue, vol. 692, 2012, pp. 5–27) have developed a new theory that balances the basic growth rate with that of secondary instabilities that act on the finite amplitude fingers. Their approach promises a way forward for computationally challenging systems with vastly different scales of decay for momentum, heat and dissolved substances.

scholarly journals Reply

2008 ◽  
Vol 65 (3) ◽  
pp. 1095-1097 ◽  
Author(s):  
David M. Schultz ◽  
Adam J. Durant ◽  
Jerry M. Straka ◽  
Timothy J. Garrett
Keyword(s):  
Volcanic Ash ◽  
Effective Means ◽  
Double Diffusive Convection ◽  
Vertical Temperature ◽  
Effective Mechanism ◽  
Gravitational Forces ◽  
Salt Fingers ◽  
Diffusive Convection ◽  
Double Diffusive

Abstract Doswell has proposed a mechanism for mammatus called double-diffusive convection, the mechanism responsible for salt fingers in the ocean. The physics of salt fingers and mammatus are different. Unlike the ocean where the diffusivity is related to molecular motions within solution, the hydrometeors in clouds are affected by inertial and gravitational forces. Doswell misinterprets the vertical temperature profiles through mammatus and fails to understand the role of settling in volcanic ash clouds. Furthermore, given that mixing is a much more effective means of transferring heat in the atmosphere and given idealized numerical model simulations of mammatus showing that the destabilizing effect of subcloud sublimation is an effective mechanism for mammatus, this reply argues that double-diffusive convection is unlikely to explain mammatus, either in cumulonimbus anvils or in volcanic ash clouds.

The Influence of Coupled Molecular Diffusion on Double-Diffusive Convection in a Porous Medium

1986 ◽  
Vol 108 (4) ◽  
pp. 872-876 ◽  
Author(s):  
N. Rudraiah ◽  
M. S. Malashetty
Keyword(s):  
Porous Medium ◽  
Molecular Diffusion ◽  
Normal Mode Analysis ◽  
Finite Amplitude ◽  
Mode Analysis ◽  
Double Diffusive Convection ◽  
Amplitude Analysis ◽  
Cross Diffusion ◽  
Diffusive Convection ◽  
Double Diffusive

The effect of coupled molecular diffusion on double-diffusive convection in a horizontal porous medium is studied using linear and nonlinear stability analyses. In the case of linear theory, normal mode analysis is employed incorporating two cross diffusion terms. It is found that salt fingers can form by taking cross-diffusion terms of appropriate sign and magnitude even when both concentrations are stably stratified. The conditions for the diffusive instability are compared with those for the formation of fingers. It is shown that these two types of instability will never occur together. The finite amplitude analysis is used to derive the condition for the maintenance of fingers. The stability boundaries are drawn for three different combinations of stratification and the effect of permeability is depicted.

scholarly journals Bounds for the growth of a perturbation in some double-diffusive convection problems

1983 ◽  
Vol 25 (2) ◽  
pp. 276-285 ◽  
Author(s):  
J. R. Gupta ◽  
S. K. Sood ◽  
R. G. Shandil ◽  
M. B. Banerjee ◽  
K. Banerjee
Keyword(s):  
Growth Rate ◽  
Fluid Mechanics ◽  
Newtonian Fluid ◽  
Double Diffusive Convection ◽  
Diffusive Convection ◽  
Complex Growth Rate ◽  
Double Diffusive

AbstractBounds are presented for the modulus of the complex growth rate p of an arbitrary oscillatory perturbation, neutral or unstable, in some double-diffusive problems of relevance in oceanography, astrophysics and non-Newtonian fluid mechanics.

scholarly journals Video: Salt fingers in double diffusive convection bounded by two parallel plates

2014 ◽  
Author(s):  
Yantao Yang ◽  
Erwin P. van der Poel ◽  
Rodolfo Ostilla-Monico ◽  
Chao Sun ◽  
Roberto Verzicco ◽  
...  
Keyword(s):  
Double Diffusive Convection ◽  
Parallel Plates ◽  
Salt Fingers ◽  
Diffusive Convection ◽  
Double Diffusive

Equilibrium transport in double-diffusive convection

2011 ◽  
Vol 692 ◽  
pp. 5-27 ◽  
Author(s):  
Timour Radko ◽  
D. Paul Smith
Keyword(s):  
Linear Growth ◽  
Density Ratio ◽  
Molecular Characteristics ◽  
Diffusive Transport ◽  
Salt Fingers ◽  
Diffusive Convection ◽  
Wide Range ◽  
Secondary Instabilities ◽  
Double Diffusive

AbstractA theoretical model for the equilibrium double-diffusive transport is presented which emphasizes the role of secondary instabilities of salt fingers in saturation of their linear growth. Theory assumes that the fully developed equilibrium state is characterized by the comparable growth rates of primary and secondary instabilities. This assumption makes it possible to formulate an efficient algorithm for computing diffusivities of heat and salt as a function of the background property gradients and molecular parameters. The model predicts that the double-diffusive transport of heat and salt rapidly intensifies with decreasing density ratio. Fluxes are less sensitive to molecular characteristics, mildly increasing with Prandtl number $(\mathit{Pr})$ and decreasing with diffusivity ratio $(\tau )$. Theory is successfully tested by a series of direct numerical simulations which span a wide range of $\mathit{Pr}$ and $\tau $.

Double-diffusive convection in magma chambers: Single or multiple layers?

1986 ◽  
Vol 13 (2) ◽  
pp. 153-156 ◽  
Author(s):  
Frank J. Spera ◽  
David A. Yuen ◽  
Stephen Clark ◽  
H.-J. Hong
Keyword(s):  
Double Diffusive Convection ◽  
Magma Chambers ◽  
Diffusive Convection ◽  
Double Diffusive
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