scholarly journals Rayleigh-Bénard convection of a model emulsion: anomalous heat-flux fluctuations and finite-size droplets effects

Soft Matter ◽  
2021 ◽  
Author(s):  
Francesca Pelusi ◽  
Mauro Sbragaglia ◽  
Roberto Benzi ◽  
Andrea Scagliarini ◽  
Massimo Bernaschi ◽  
...  
Keyword(s):  
Heat Flux ◽  
Numerical Simulations ◽  
Finite Size ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Two Dimensional Model ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Model Emulsion ◽  
Anomalous Heat

We present mesoscale numerical simulations of Rayleigh-Bénard (RB) convection in a two-dimensional model emulsion. The systems under study are constituted of finite-size droplets, whose concentration Ψ0 is systematically varied from...

A model for the emergence of thermal plumes in Rayleigh–Bénard convection at infinite Prandtl number

2000 ◽  
Vol 414 ◽  
pp. 225-250 ◽  
Author(s):  
C. LEMERY ◽  
Y. RICARD ◽  
J. SOMMERIA
Keyword(s):  
Prandtl Number ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Thermal Plumes ◽  
Bénard Convection ◽  
Benard Convection ◽  
Two Dimensional Model ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

We propose a two-dimensional model of three-dimensional Rayleigh–Bénard convection in the limit of very high Prandtl number and Rayleigh number, as in the Earth's mantle. The model equation describes the evolution of the first moment of the temperature anomaly in the thermal boundary layer, which is assumed thin with respect to the scale of motion. This two-dimensional field is transported by the velocity that it induces and is amplified by surface divergence. This model explains the emergence of thermal plumes, which arise as finite-time singularities. We determine critical exponents for these singularities. Using a smoothing method we go beyond the singularity and reach a stage of developed convection. We describe a process of plume merging, leaving room for the birth of new instabilities. The heat flow at the surface predicted by our two-dimensional model is found to be in good agreement with available data.

scholarly journals Energy and Variance Budgets of a Diffusive Staircase with Implications for Heat Flux Scaling

2016 ◽  
Vol 46 (8) ◽  
pp. 2553-2569 ◽  
Author(s):  
Magnus Hieronymus ◽  
Jeffrey R. Carpenter
Keyword(s):  
Heat Flux ◽  
Numerical Simulations ◽  
Scaling Laws ◽  
State Energy ◽  
Diffusive Regime ◽  
Diffusive Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Numbers ◽  
Rayleigh Benard ◽  
Double Diffusive

AbstractThe steady-state energy and thermal variance budgets form the basis for most current methods for evaluating turbulent fluxes of buoyancy, heat, and salinity. This study derives these budgets for a double-diffusive staircase and quantifies them using direct numerical simulations; 10 runs with different Rayleigh numbers are considered. The energy budget is found to be well approximated by a simple three-term balance, while the thermal variance budget consists of only two terms. The two budgets are also combined to give an expression for the ratio of the heat and salt fluxes. The heat flux scaling is also studied and found to agree well with earlier estimates based on laboratory experiments and numerical simulations at high Rayleigh numbers. At low Rayleigh numbers, however, the authors find large deviations from earlier scaling laws. Last, the scaling theory of Grossman and Lohse, which was developed for Rayleigh–Bénard convection and is based on the partitioning of the kinetic energy and tracer variance dissipation, is adapted to the diffusive regime of double-diffusive convection. The predicted heat flux scalings are compared to the results from the numerical simulations and earlier estimates.

scholarly journals A two-dimensional model of the methane cycle in a sedimentary accretionary wedge

2012 ◽  
Vol 9 (8) ◽  
pp. 3323-3336 ◽  
Author(s):  
D. E. Archer ◽  
B. A. Buffett
Keyword(s):  
Heat Flux ◽  
Passive Margin ◽  
Model Description ◽  
Accretionary Wedge ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Methane Cycle ◽  
Active Margin ◽  
Two Dimensional Model ◽  
The Impact

Abstract. A two-dimensional model of sediment column geophysics and geochemistry has been adapted to the problem of an accretionary wedge formation, patterned after the margin of the Juan de Fuca plate as it subducts under the North American plate. Much of the model description is given in a companion paper about the application of the model to an idealized passive margin setting; here we build on that formulation to simulate the impact of the sediment deformation, as it approaches the subduction zone, on the methane cycle. The active margin configuration of the model shares sensitivities with the passive margin configuration, in that sensitivities to organic carbon deposition and respiration kinetics, and to vertical bubble transport and redissolution in the sediment, are stronger than the sensitivity to ocean temperature. The active margin simulation shows a complex sensitivity of hydrate inventory to plate subduction velocity, with results depending strongly on the geothermal heat flux. In low heat-flux conditions, the model produces a larger inventory of hydrate per meter of coastline in the passive margin than active margin configurations. However, the local hydrate concentrations, as pore volume saturation, are higher in the active setting than in the passive, as generally observed in the field.

scholarly journals Weak attractors and invariant sets in Lorenz model

2011 ◽  
Vol 24 (2) ◽  
pp. 271-280 ◽  
Author(s):  
Ilhem Djellit ◽  
Amel Hachemi-Kara
Keyword(s):  
Numerical Simulations ◽  
Parameter Space ◽  
Complex Dynamics ◽  
Invariant Sets ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Lorenz Model ◽  
Two Dimensional Model

A two-dimensional model is analyzed. It reflects the dynamics occurring in discrete Lorenz model. Invariant sets are analytically detected and the parameter space is investigated in order to classify completely regions of existence of stable 2-cycles, and regions associated with chaotic behaviors. This paper describes complex dynamics of invariant sets and weak attractors according to Tsybulin and Yudovich idea. These sets are displayed by numerical simulations.

IS THERE A DELOCALISATION TRANSITION IN A TWO-DIMENSIONAL MODEL FOR QUANTUM PERCOLATION?

1992 ◽  
Vol 06 (13) ◽  
pp. 817-821 ◽  
Author(s):  
INDRA DASGUPTA ◽  
TANUSRI SAHA ◽  
ABHIJIT MOOKERJEE ◽  
B. K. CHAKRABARTI
Keyword(s):  
Finite Size ◽  
Two Dimensions ◽  
Percolation Model ◽  
Square Lattice ◽  
Two Dimensional ◽  
Finite Size Scaling ◽  
Dimensional Model ◽  
Recursion Method ◽  
Quantum Percolation ◽  
Two Dimensional Model

We estimate the transmittance of the quantum percolation model of Eggarter and Kirkpatrick (1972) on the square lattice of various sizes using the vector recursion method. We note from finite size scaling that there is no delocalisation transition for any degree of disorder in two dimensions.

Commitment to pro- versus counter-attitudinal behavior and the dynamics of social representations

2002 ◽  
Vol 61 (1) ◽  
pp. 34-44 ◽  
Author(s):  
Eric Tafani ◽  
Lionel Souchet
Keyword(s):  
Higher Education ◽  
Social Representations ◽  
Cognitive Restructuring ◽  
Social Representation ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Social Actions ◽  
The Social ◽  
Two Dimensional Model ◽  
Students Attitudes

This research uses the counter-attitudinal essay paradigm ( Janis & King, 1954 ) to test the effects of social actions on social representations. Thus, students wrote either a pro- or a counter-attitudinal essay on Higher Education. Three forms of counter-attitudinal essays were manipulated countering respectively a) students’ attitudes towards higher education; b) peripheral beliefs or c) central beliefs associated with this representation object. After writing the essay, students expressed their attitudes towards higher education and evaluated different beliefs associated with it. The structural status of these beliefs was also assessed by a “calling into question” test ( Flament, 1994a ). Results show that behavior challenging either an attitude or peripheral beliefs induces a rationalization process, giving rise to minor modifications of the representational field. These modifications are only on the social evaluative dimension of the social representation. On the other hand, when the behavior challenges central beliefs, the same rationalization process induces a cognitive restructuring of the representational field, i.e., a structural change in the representation. These results and their implications for the experimental study of representational dynamics are discussed with regard to the two-dimensional model of social representations ( Moliner, 1994 ) and rationalization theory ( Beauvois & Joule, 1996 ).

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