Boundary layers and normal mode parameters in a system with double-diffusive convection at large Rayleigh numbers

2016 ◽  
Author(s):  
Sergey B. Kozitskiy ◽  
Mikhail Yu. Trofimov ◽  
Alena D. Zakharenko
Keyword(s):  
Boundary Layers ◽  
Normal Mode ◽  
Double Diffusive Convection ◽  
Diffusive Convection ◽  
Rayleigh Numbers ◽  
Double Diffusive

scholarly journals Double-Diffusive Convection in Presence of Compressible Rivlin-Ericksen Fluid with Fine Dust

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Mahinder Singh ◽  
Rajesh Kumar Gupta
Keyword(s):  
Normal Modes ◽  
Suspended Particles ◽  
Double Diffusive Convection ◽  
Fine Dust ◽  
Stationary Convection ◽  
Viscoelastic Parameter ◽  
Diffusive Convection ◽  
Rayleigh Numbers ◽  
Solute Gradient ◽  
Double Diffusive

An investigation is made on the effect of suspended particles (fine dust) on double-diffusive convection of a compressible Rivlin-Ericksen elastico-viscous fluid. The perturbation equations are analyzed in terms of normal modes after linearizing the relevant set of equations. A dispersion relation governing the effects of viscoelasticity, compressibility, stable solute gradient, and suspended particles is derived. For stationary convection, Rivlin-Ericksen fluid behaves like an ordinary Newtonian fluid due to the vanishing of the viscoelastic parameter. The stable solute gradient compressibility has a stabilizing effect on the system whereas suspended particles hasten the onset of thermosolutal instability. The Rayleigh numbers and the wave numbers of the associated disturbances for the onset of instability as stationary convection are obtained and the behaviour of various parameters on Rayleigh numbers has been depicted graphically. It has been observed that oscillatory modes are introduced due to the presence of viscoelasticity, suspended particles, and stable solute gradient which were not existing in the absence of these parameters.

Double-Diffusive Convection

2013 ◽  
Author(s):  
Gary A. Glatzmaier
Keyword(s):  
Oscillation Amplitude ◽  
Marginal Stability ◽  
Double Diffusive Convection ◽  
Diffusive Convection ◽  
Nonlinear Simulations ◽  
Fingering Instability ◽  
Zero Growth ◽  
Salt Fingering ◽  
Rayleigh Numbers ◽  
Double Diffusive

This chapter discusses double-diffusive convection, with a particular focus on the initial instability and eventual nonlinear evolution. It first considers the “salt-fingering” instability and then the “semiconvection” instability before discussing the possibility that the onsets of these instabilities at marginal stability have an amplitude that oscillates in time. The goal is to find the conditions that would result in a zero growth rate of the oscillation amplitude in order to determine the marginal stability constraint on the Rayleigh numbers for the onset of an oscillating instability. The chapter also shows how, after evolving beyond the onset of the instability, thermal diffusion between the moving parcel and the surroundings can alter the initial linear vertical profile of the horizontal-mean temperature into a “staircase” profile. This evolution of the temperature profile is investigated via nonlinear simulations.

scholarly journals Rotating double-diffusive convection in stably stratified planetary cores

2019 ◽  
Vol 219 (Supplement_1) ◽  
pp. S195-S218 ◽  
Author(s):  
R Monville ◽  
J Vidal ◽  
D Cébron ◽  
N Schaeffer
Keyword(s):  
Large Scale ◽  
Critical Rayleigh Number ◽  
Marginal Stability ◽  
Early Earth ◽  
Double Diffusive Convection ◽  
Earth Core ◽  
Diffusive Convection ◽  
Non Linear ◽  
Rayleigh Numbers ◽  
Double Diffusive

SUMMARY In planetary fluid cores, the density depends on temperature and chemical composition, which diffuse at very different rates. This leads to various instabilities, bearing the name of double-diffusive convection (DDC). We investigate rotating DDC (RDDC) in fluid spheres. We use the Boussinesq approximation with homogeneous internal thermal and compositional source terms. We focus on the finger regime, in which the thermal gradient is stabilizing whereas the compositional one is destabilizing. First, we perform a global linear stability analysis in spheres. The critical Rayleigh numbers drastically drop for stably stratified fluids, yielding large-scale convective motions where local analyses predict stability. We evidence the inviscid nature of this large-scale double-diffusive instability, enabling the determination of the marginal stability curve at realistic planetary regimes. In particular, we show that in stably stratified spheres, the Rayleigh numbers Ra at the onset evolve like Ra ∼ Ek−1, where Ek is the Ekman number. This differs from rotating convection in unstably stratified spheres, for which Ra ∼ Ek−4/3. The domain of existence of inviscid convection thus increases as Ek−1/3. Secondly, we perform non-linear simulations. We find a transition between two regimes of RDDC, controlled by the strength of the stratification. Furthermore, far from the RDDC onset, we find a dominating equatorially antisymmetric, large-scale zonal flow slightly above the associated linear onset. Unexpectedly, a purely linear mechanism can explain this phenomenon, even far from the instability onset, yielding a symmetry breaking of the non-linear flow at saturation. For even stronger stable stratification, the flow becomes mainly equatorially symmetric and intense zonal jets develop. Finally, we apply our results to the early Earth core. Double diffusion can reduce the critical Rayleigh number by four decades for realistic core conditions. We suggest that the early Earth core was prone to turbulent RDDC, with large-scale zonal flows.

DOUBLE-DIFFUSIVE CONVECTION IN LIQUID FREON

1998 ◽  
Author(s):  
Pierre Dupont ◽  
O. Gorieu ◽  
Hassan Peerhossaini ◽  
M. Kestoras
Keyword(s):  
Double Diffusive Convection ◽  
Diffusive Convection ◽  
Double Diffusive
Sign in / Sign up

Export Citation Format

Share Document