204 results on '"THERMOSOLUTAL CONVECTION"'
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2. Onset of triple diffusive thermosolutal convection in a composite system
- Author
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Ramakrishna Sumithra and Basavarajappa Komala
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Fluid Flow and Transfer Processes ,Condensed Matter Physics - Published
- 2023
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3. THERMOSOLUTAL CONVECTION IN A BIDISPERSE POROUS MEDIUM WITH CHEMICAL REACTION EFFECT AND RELATIVELY LARGE MACROPORES
- Author
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Alaa Jabbar Badday and Akil J. Harfash
- Subjects
Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,Biomedical Engineering ,General Materials Science ,Condensed Matter Physics - Abstract
The model of double diffusive convection in a bidisperse porous medium was examined. Brinkman effects and slip were allowed to be used in macropores. In the micropores, only the Darcy effects are held. In equilibrium, the concentration of solutes is thought to be a linear function of temperature. We performed both a linear and a nonlinear stability analysis, with a particular emphasis on the impact of slip boundary conditions on the system's instability and stability. After deciding when the instability started, we determined the critical Rayleigh number as a function of the slip coefficient. Numerical findings for stability/instability thresholds were also presented. more...
- Published
- 2023
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4. Dual rotations of rods on thermosolutal convection in a porous cavity suspended by nanoencapsulated phase change materials
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Weaam Alhejaili and Abdelraheem M. Aly
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Statistical and Nonlinear Physics ,Condensed Matter Physics - Abstract
The fractional of a time derivative for the incompressible smoothed particle hydrodynamics (ISPH) method is adopted to handle thermal radiation on thermosolutal convection in a porous cavity barred by nanoencapsulated phase change materials (NEPCMs). A novel work on the rotational velocities of two rods during thermosolutal convection of NEPCMs within a novel cavity of two connected circular cylinders is introduced. The management of heat-mass transfer and velocity magnitude inside distinct designed materials below various boundary conditions carries improvements for energy efficiency. The physical factors are thermal radiation [Formula: see text], Fusion temperature [Formula: see text], Rayleigh number [Formula: see text], hot source length [Formula: see text], Darcy number [Formula: see text], and fractional order parameter [Formula: see text]. This study reported the role of thermal/solutal conditions in varying the dual convection flow and heat capacity contour. The lower Da provides an elevated porous resistance which decelerates the nanofluid velocity. The fusion temperature alters a heat capacity contour. more...
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- 2023
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5. Onset of Linear and Nonlinear Thermosolutal Convection with Soret and Dufour Effects in a Porous Collector under a Uniform Magnetic Field
- Author
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Noureddine Hadidi, Mahmoud Mamou, and Redha Rebhi
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Convection ,Materials science ,Buoyancy ,020209 energy ,porous cavity ,magnetic field ,02 engineering and technology ,engineering.material ,01 natural sciences ,010305 fluids & plasmas ,Soret ,Physics::Fluid Dynamics ,thermosolutal convection ,Mass transfer ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Hopf bifurcation ,Adiabatic process ,Physics::Atmospheric and Oceanic Physics ,Fluid Flow and Transfer Processes ,QC120-168.85 ,Dufour ,Mechanical Engineering ,Mechanics ,Condensed Matter Physics ,Magnetic field ,Descriptive and experimental mechanics ,Heat transfer ,engineering ,Thermodynamics ,QC310.15-319 ,Porous medium ,Intensity (heat transfer) - Abstract
The present paper reports on an analytical and numerical study of combined Soret and Dufour effects on thermosolutal convection in a horizontal porous cavity saturated with an electrically conducting binary fluid under a magnetic field. The horizontal walls of the system are subject to vertical uniform fluxes of heat and mass, whereas the vertical walls are assumed to be adiabatic and impermeable. The main governing parameters of the problem are the Rayleigh, the Hartmann, the Soret, the Dufour and the Lewis numbers, the buoyancy ratio, the enclosure aspect ratio, and the normalized porosity of the porous medium. An asymptotic parallel flow approximation is applied to determine the onset of subcritical nonlinear convection. In addition, a linear stability analysis is performed to predict explicitly the thresholds for the onset of stationary, overstable and oscillatory convection, and the Hopf bifurcation as functions of the governing parameters. The combined effect of a magnetic field, Soret and Dufour parameters have a noticeable influence on the intensity of the convective flow, the heat and mass transfer rates, and the thresholds of linear convection. It is found that the imposition of a magnetic field delays the onset of convection and its intensification can lead to the total suppression of the convective currents. The heat transfer rate increases with the Dufour number and decreases with the Soret number and vice versa for the mass transfer rate. more...
- Published
- 2021
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6. THERMOSOLUTAL CONVECTION IN A BRINKMAN POROUS MEDIUM WITH REACTION AND SLIP BOUNDARY CONDITIONS
- Author
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Akil J. Harfash and Alaa Jabbar Badday
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Convection ,Materials science ,Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,Biomedical Engineering ,General Materials Science ,Boundary value problem ,Mechanics ,Slip (materials science) ,Condensed Matter Physics ,Porous medium ,Chemical reaction - Published
- 2022
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7. Macrosegregation and thermosolutal convection-related freckle formation in directionally solidified Sn–Ni peritectic alloy in crucibles with different diameters
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Sheng-yuan Li, Li Lu, Shudong Zhou, Wanchao Zheng, and Peng Peng
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Convection ,Zone melting ,Work (thermodynamics) ,Materials science ,Morphology (linguistics) ,Metallurgy ,Alloy ,Metals and Alloys ,Rayleigh number ,engineering.material ,Geotechnical Engineering and Engineering Geology ,Condensed Matter Physics ,Temperature gradient ,Materials Chemistry ,engineering ,Directional solidification - Abstract
Different from other alloys, the observation in this work on the dendritic mushy zone shows that the freckles are formed in two different regions before and after peritectic reaction in directional solidification of Sn–Ni peritectic alloys. In addition, the experimental results demonstrate that the dendritic morphology is influenced by the temperature gradient zone melting and Gibbs–Thomson effects. A new Rayleigh number (RaP) is proposed in consideration of both effects and peritectic reaction. The prediction of RaP confirms the freckle formation in two regions during peritectic solidification. Besides, heavier thermosolutal convection in samples with larger diameter is also demonstrated. more...
- Published
- 2021
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8. Weakly Nonlinear Stability of Thermosolutal Convection in an Oldroyd-B Fluid-Saturated Anisotropic Porous Layer Using a Local Thermal Nonequilibrium Model
- Author
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C. Hemanth Kumar, B. M. Shankar, and I. S. Shivakumara
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Physics::Fluid Dynamics ,Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Abstract
The two-temperature model of local thermal nonequilibrium (LTNE) is utilized to investigate a weakly nonlinear stability of thermosolutal convection in an Oldroyd-B fluid-saturated anisotropic porous layer. The anisotropies in permeability, thermal conductivities of the porous medium, and solutal diffusivity are accounted for by second-order tensors with their principal directions coinciding with the horizontal and vertical coordinate axes. A modified Darcy–Oldroyd model is employed to describe the flow in a porous medium bounded by impermeable plane walls with uniform and unequal temperatures as well as solute concentrations. The cubic-Landau equations are derived in the neighborhood of stationary and oscillatory onset using a modified perturbation approach and the stability of bifurcating equilibrium solutions is discussed. The advantage is taken to present some additional results on the linear instability aspects as well. It is manifested that the solutal anisotropy parameter also plays a decisive role on the instability characteristics of the system. It is found that the stationary bifurcating solution transforms from supercritical to subcritical while the oscillatory bifurcating solution transforms from supercritical to subcritical and revert to supercritical. The Nusselt and Sherwood numbers are used to examine the influence of LTNE and viscoelastic parameters on heat and mass transfer, respectively. The results of Maxwell fluid are outlined as a particular case from this study. more...
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- 2022
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9. Three-Dimensional Numerical Simulation and Experimental Investigations of Benchmark Experiment of Sn-10 wt. %Pb Alloy Solidification Under Thermosolutal Convection
- Author
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Ab. Abdelhakem, Ab. Nouri, L. Hachani, Y. Fautrelle, and K. Zaidat
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Abstract
A full three-dimensional (3D) numerical simulation of solidification was carried out for a benchmark experiment on a binary Sn-10 wt. %Pb alloy. The experiment process involves a melting stage, a first holding stage at constant temperature with electromagnetic stirring, setting a mean horizontal temperature difference (second holding stage), and finally solidification stage by decreasing the temperature under a imposed horizontal temperature gradient. The numerical model is applied only to investigate the solidification stage and compared with the measured temperature fields and macrosegregation obtained from the postmortem analysis. A columnar numerical model based on a two-phase volume-averaged approach is used for the numerical simulation, accounting for thermosolutal convection and assuming perfect microscopic mixing (lever rule) in the mushy zone. It demonstrates that such a model is able to predict stratification in the solute from the liquid phase and mushy zone during the solidification. The effect of the sedimentation on macrosegregations and channel segregation or freckles which develop during the solidification stage is also predicted by the model and compared with experimental data. Emphasis is given to the main factors that have a direct effect on the development and morphology of segregated channels, namely, the remelting phenomenon, dendrite fragmentation, and the solidification front instabilities. more...
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- 2022
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10. The effects of the Soret and slip boundary conditions on thermosolutal convection with a Navier–Stokes–Voigt fluid
- Author
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Akil Harfash and Alaa Jabbar Badday
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Fluid Flow and Transfer Processes ,Mechanics of Materials ,Mechanical Engineering ,Computational Mechanics ,Condensed Matter Physics - Abstract
In this paper, we study the problem of thermosolutal convection in a Navier–Stokes–Voigt fluid when the layer is heated from below and simultaneously salted from above or below. This problem is studied under the effects of Soret and slip boundary conditions. Both linear and nonlinear stability analyses are employed. When the layer is heated from below and salted from above, the boundaries exhibit great concordance, resulting in a very narrow region of probable subcritical instabilities. This proves that linear analysis is reliable enough to forecast the beginning of convective motion. The Chebyshev collocation technique and QZ algorithm have been used to solve systems of linear and nonlinear theories. For thermal convection in a dissolved salt field with a complex viscoelastic fluid of the Navier–Stokes–Voigt type, instability boundaries are computed. When the convection is of the oscillatory type, the Kelvin–Voigt parameter is observed to play a crucial role in functioning as a stabilizing agent. This effect's quantitative size is shown. more...
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- 2023
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11. Thermosolutal convection and macrosegregation during directional solidification of TiAl alloys in centrifugal casting
- Author
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Miha Založnik, Martín Cisternas Fernández, Ulrike Hecht, Hervé Combeau, Institut Jean Lamour (IJL), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), and Access e.V. more...
- Subjects
Convection ,Gravity (chemistry) ,Materials science ,Buoyancy ,02 engineering and technology ,engineering.material ,7. Clean energy ,01 natural sciences ,[SPI.MAT]Engineering Sciences [physics]/Materials ,[SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] ,010305 fluids & plasmas ,macrosegregation ,thermosolutal convection ,Centrifugal casting (industrial) ,0103 physical sciences ,Directional solidification ,Fluid Flow and Transfer Processes ,Centrifuge ,Mechanical Engineering ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Rotating reference frame ,Titanium-aluminide alloys ,[INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation ,Boussinesq approximation (buoyancy) ,centrifugal casting ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,engineering ,0210 nano-technology - Abstract
International audience; Experiments of directional solidification of TiAl cylindrical samples were conducted within the frame of the ESA GRADECET project. The experiments were performed in the ESA "Large Diameter Centrifuge" using a furnace with a well defined thermal protocol. The furnace was mounted in the centrifuge and free to tilt in such a way that the total apparent gravity (sum of terrestrial gravity and centrifugal acceleration) was aligned to the cylinder centerline. Several centrifugation levels were investigated besides to one reference case out of the centrifuge. In this work, we present 3D numerical simulations of these experiments paying special attention in the liquid thermosolutal buoyancy convection and aluminum macrosegregation. The numerical model accounts for the non-inertial accelerations that appear in the rotating reference frame (centrifugal and Coriolis), motionless solid, the-mosolutal Boussinesq approximation and an infinitely fast microscopic diffusion model between the phases to depict the solid growth. The results showed that the Coriolis acceleration entirely modifies the liquid flow regime during solidification leading to a 3D aluminum segregation pattern with respect to the case solidified under normal terrestrial gravity conditions. Additionally the magnitude of aluminum segregation increases with the level of centrifu-* Corresponding author more...
- Published
- 2020
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12. Bistability bifurcation phenomenon induced by non-Newtonian fluids rheology and thermosolutal convection in Rayleigh–Bénard convection
- Author
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Redha Rebhi, Mahmoud Mamou, and Noureddine Hadidi
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Fluid Flow and Transfer Processes ,Physics ,Convection ,Bistability ,Mechanical Engineering ,Computational Mechanics ,Finite difference method ,Mechanics ,Condensed Matter Physics ,Boussinesq approximation (buoyancy) ,Non-Newtonian fluid ,Physics::Fluid Dynamics ,Mechanics of Materials ,Thermal ,Newtonian fluid ,Rayleigh–Bénard convection - Abstract
In the present paper, a numerical investigation was performed to assess the effect of the rheological behavior of non-Newtonian fluids on Rayleigh–Benard thermosolutal convection instabilities within shallow and finite aspect ratio enclosures. Neumann and Dirichlet thermal and solutal boundary condition types were applied on the horizontal walls of the enclosure. Using the Boussinesq approximation, the momentum, energy, and species transport equations were numerically solved using a finite difference method. Performing a nonlinear asymptotic analysis, a bistability convective phenomenon was discovered, which was induced by the combined fluid shear-thinning and aiding thermosolutal convection effects. Therefore, bistability convection was the main focus in the current study using the more practical constitutive Carreau–Yasuda viscosity model, which is valid from zero to infinite shear rates. Also, the combined effects of the rheology parameters and double diffusive bistability convection were studied. For aiding flow, the shear-thinning and the slower diffusing solute effects were counteracting and, as a result, two steady-state finite amplitude solutions were found to exist for the same values of the governing parameters, which indicated and demonstrated evidence for the existence of bistability convective flows. For opposing flows, the shear-thinning effect strengthened subcritical flows, which sustained well below the threshold of Newtonian thermosolutal convection. Thus, bistability convection did not exist for opposing flows, as both the shear-thinning and the slower diffusing component effects favored subcritical convection. more...
- Published
- 2021
13. Thermosolutal convection under cross-diffusion effect in SGSP with porous layer
- Author
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Jiang-Tao Hu and Shuo-Jun Mei
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics ,Civil and Structural Engineering - Published
- 2022
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14. Three-dimensional Lattice Boltzmann simulation on thermosolutal convection and entropy generation of Carreau-Yasuda fluids
- Author
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Hui Tang and Gh.R. Kefayati
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Fluid Flow and Transfer Processes ,Convection ,Buoyancy ,Materials science ,Natural convection ,Mechanical Engineering ,Lattice Boltzmann methods ,02 engineering and technology ,Rayleigh number ,Mechanics ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Bejan number ,Lewis number ,010305 fluids & plasmas ,Mass transfer ,0103 physical sciences ,engineering ,0210 nano-technology - Abstract
In this paper, three-dimensional thermosolutal natural convection and entropy generation in a cubic cavity filled with a non-Newtonian Carreau-Yasuda fluid has been simulated by Lattice Boltzmann Method (LBM). This study has been conducted for certain pertinent parameters of Rayleigh number (Ra = 104 and 105), the Buoyancy ratio (N = -1, 0.1, 1), the Lewis number (Le = 0.5, 2.5, 10, 100, and 1000), power-law indexes (n = 0.5, 1, and 1.5), Carreau number (Cu = 0.01, 0.1, 1, 10 and 100), and Carreau-Yasuda parameter (m = 0.1, 0.5, and 1). Results indicate that the rise of Rayleigh number enhances heat and mass transfer for various studied parameters. The increase in power-law index provokes heat and mass transfer to drop gradually. However, the effect of power-law index on heat and mass transfer rises steadily as Rayleigh number rises. The enhancement of Carreau number decreases heat and mass transfer, but; the increases in the Carreau-Yasuda parameter augments heat and mass transfer significantly. The augmentation of the buoyancy ratio number enhances heat and mass transfer. It was found that mass transfer increases as Lewis number augments. The augmentation of Rayleigh number enhances different entropy generations and declines the average Bejan number. The increase in the power-law index provokes various irreversibilities to drop significantly. The enhancement of the buoyancy ratio causes the summation entropy generations to increase considerably. The rise of Carreau number and Carreau-Yasuda parameter decreases and increases the total irreversibilities; respectively. more...
- Published
- 2019
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15. Micropolar nanofluid overlying a porous layer: Thermosolutal convection
- Author
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Jawali Channabasappa Umavathi
- Subjects
General Materials Science ,Electrical and Electronic Engineering ,Condensed Matter Physics - Abstract
An investigation of the stability of an micropolar nanofluid overlying a sparsely packed porous medium and implanted in a parallel conduit is reviewed. Linear and also nonlinear terms are incorporated for the study. A Darcy-Brinkman-Forchheimer drag force model is deployed. To evaluate nanoscale effects the Buongiorno model is employed. The equations for mass, momentum, angular momentum, energy and nanoparticle species conservation with correlated wall conditions are non-dimensionalized. Modified diffusivity ratio and Lewis number stable the system, the micropolar parameters concentration Rayleigh number destable system for stationary convection. Concentration Rayleigh number, micropolar parameters stabilize and Lewis number destabilizes the system for oscillatory convection. Applications of the study include micro/nano-fluidic devices, nano-doped energy systems and packed beds in chemical engineering. more...
- Published
- 2022
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16. Multiple-Relaxation-Time Lattice Boltzmann method for thermosolutal convection in Czchralski silicon crystal growth
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Wang Jing and Huang Weichao
- Subjects
Convection ,Monocrystalline silicon ,Materials science ,Condensed matter physics ,Lattice Boltzmann methods - Published
- 2021
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17. Impact of thermal and solute source-sink combination on thermosolutal convection in a partially active porous annulus
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S Kemparaju, H A Kumara Swamy, M Sankar, and F Mebarek-Oudina
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Condensed Matter Physics ,Mathematical Physics ,Atomic and Molecular Physics, and Optics - Abstract
The objective of the current paper is to investigate the thermosolutal flow along with heat and mass dissipation rates in an upright porous annular space subjected to discrete heating and salting along the vertical boundaries with insulated and impermeable horizontal boundaries. To solve the model equations, an implicit finite difference scheme with over relaxation technique has been implemented. The numerical predictions focus specifically on the effect of buoyancy ratio, Lewis number, Darcy number and source-sink arrangements on fluid flow behavior, thermal and solutal characteristics, average Nusselt and Sherwood numbers. The simulations were performed for an extensive range of dimensionless parameters (−10 ≤ N ≤ 10, 0.1 ≤ Le ≤ 1, 10−5 ≤ Da ≤ 10−1) by considering two different types of source-sink arrangements and found that the flow circulation strength is maximum with in-line arrangement of source and sink compared to alternative arrangement. Also, we found that in case-I, regardless of Lewis number, the maximum heat and mass dissipation rates takes place through top source during opposing flow, and through bottom source for aided flow. However, in case-II arrangement, irrespective to type of flow, the greater amount of heat and mass transport is found through the bottom source at the inner cylinder compared to top source placed at outer cylinder. more...
- Published
- 2022
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18. Cellular automaton modeling of dendritic growth of Fe-C binary alloy with thermosolutal convection
- Author
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Weiling Wang, Sen Luo, and Miaoyong Zhu
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010302 applied physics ,Fluid Flow and Transfer Processes ,Equiaxed crystals ,Convection ,Buoyancy ,Materials science ,Quantitative Biology::Neurons and Cognition ,Advection ,Mechanical Engineering ,Thermodynamics ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Boussinesq approximation (buoyancy) ,Vortex ,Physics::Fluid Dynamics ,Dendrite (crystal) ,0103 physical sciences ,Thermal ,engineering ,0210 nano-technology - Abstract
Embedded the thermal and solutal buoyancy into the momentum conservation equation as an additional force term using the Boussinesq approximation, a 2D CA-FVM model is extended to simulate the dendritic growth with thermosolutal convection. The model is firstly validated by comparison of numerical predictions with the benchmark test of Rayleigh – Benard convection and the analytical solutions of the stagnant film model for the free dendritic growth with thermosolutal convection, and good agreements between the numerical results with analytical solutions are obtained. Later, numerical simulations for both the equiaxed and columnar dendritic growth of Fe-0.82wt%C binary alloy with thermosolutal convection are performed. The results show that, for the equiaxed dendritic growth in an undercooled melt, the dendrite tip growth rapidly decreases from the high velocity to a relative low steady-state value. With the further growth of dendrite, the thermosolutal convection induced by the solute rejection and latent heat release is enhanced and four vortexes are developed between the dendrite arms. Thus, the asymmetries of the dendrite morphology, temperature and solute profiles are intensified. For the columnar dendritic growth with thermosolutal convection under the unidirectional solidification process, the thermosolutal convection transports the rejected solute downward and makes the solute enrich at the interdendritic region. The thermosolutal convection facilitates the upstream dendritic growth, but inhibits the downstream dendritic growth. Moreover, with the increase of deflection angle of gravity, the advection on the top region and the clock-wise vortex flow at the interdendritic region intensified, and finally the columnar dendrite morphology becomes more asymmetrical. more...
- Published
- 2018
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19. Asymptotically exact codimension-four dynamics and bifurcations in two-dimensional thermosolutal convection at high thermal Rayleigh number: Chaos from a quasi-periodic homoclinic explosion and quasi-periodic intermittency
- Author
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Jerry F. Magnan and Justin S. Eilertsen
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Physics ,Partial differential equation ,Mathematical analysis ,Statistical and Nonlinear Physics ,Rayleigh number ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Nonlinear Sciences::Chaotic Dynamics ,Nonlinear system ,law ,Limit cycle ,Intermittency ,0103 physical sciences ,Attractor ,Homoclinic orbit ,010306 general physics ,Poincaré map - Abstract
Using a perturbation method, we solve asymptotically the nonlinear partial differential equations that govern double-diffusive convection (with heat and solute diffusing) in a two-dimensional rectangular domain near a critical point in parameter space where the linearized operator has a quadruple-zero eigenvalue. The asymptotic solution near this codimension-four point is found to depend on two slow-time-dependent amplitudes governed by two nonlinearly-coupled Van der Pol–Duffing equations. Through numerical approximation of the 3-dimensional Poincare map in the four-dimensional state space of the amplitude equations, we detect and analyze the bifurcations of the amplitude equations as the thermal Rayleigh number, R T , is increased (for R S ≪ R T , the solute Rayleigh number) with all other parameters fixed. The bifurcations observed include: Hopf, pitchfork and Neimark–Sacker bifurcations of limit cycles, symmetric and asymmetric saddle–node bifurcations of 2-tori, and reverse torus-doubling cascades. In addition, chaotic solutions are found numerically to emerge via two different types of routes: (1) a route involving a homoclinic explosion in the Poincare map and; (2) type-I intermittency routes near saddle–node bifurcations of 2-tori. The homoclinic explosion occurs when two unstable 2-tori form homoclinic connections with a saddle limit cycle, thereby creating a homoclinic butterfly in the Poincare map that leads to a discrete Lorenz-like attractor. more...
- Published
- 2018
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20. Correlating heat and mass transfer coefficients for thermosolutal convection within a porous annulus of a circular shape: case of internal pollutants spreading
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Nabila Labsi, Karim Ragui, Abdelkader Boutra, Rachid Bennacer, Youb Khaled Benkahla, Laboratoire de Mécanique et Technologie (LMT), and École normale supérieure - Cachan (ENS Cachan)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS) more...
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[PHYS]Physics [physics] ,Fluid Flow and Transfer Processes ,Convection ,Physics ,Buoyancy ,Finite volume method ,020209 energy ,[PHYS.MECA]Physics [physics]/Mechanics [physics] ,02 engineering and technology ,Mechanics ,engineering.material ,Concentric ,Condensed Matter Physics ,01 natural sciences ,Darcy–Weisbach equation ,010305 fluids & plasmas ,13. Climate action ,Mass transfer ,0103 physical sciences ,Thermal ,0202 electrical engineering, electronic engineering, information engineering ,Annulus (firestop) ,engineering ,ComputingMilieux_MISCELLANEOUS - Abstract
The main purpose of our investigation is to show the impact of pertinent parameters; such Lewis and porous thermal Rayleigh numbers as well as the buoyancy and the aspect ratios; on the double-diffusive convection phenomena which occur within a porous annulus; found between a cold (and less concentric) outer circular cylinder and a hot (and concentric) inner one, to come out with global correlations which predict the mean transfer rates in such annulus. To do so, the physical model for the momentum conservation equation is made using the Brinkman extension of the classical Darcy equation. The set of coupled equations is solved using the finite volume method and the SIMPLER algorithm. Summarizing the numerical predictions, global correlations of overall transfer within the porous annulus as a function of the governing studied parameters are set forth which predict within ±2% the numerical results. These correlations may count as a complement to previous researches done in the case a Newtonian-fluid annulus. It is to note that the validity of the computing code used was ascertained by comparing our results with the experimental data and numerical ones already available in the literature. more...
- Published
- 2018
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21. Effects of Soret and Dufour numbers on MHD thermosolutal convection of a nanofluid in a finned cavity including rotating circular cylinder and cross shapes
- Author
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Abdelraheem M. Aly and Shreen El-Sapa
- Subjects
General Chemical Engineering ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics - Published
- 2022
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22. Thermosolutal convection of nano–encapsulated phase change materials within a porous circular cylinder containing crescent with periodic side-wall temperature and concentration: ISPH simulation
- Author
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Zehba A.S. Raizah and Abdelraheem M. Aly
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Convection ,Phase change ,Materials science ,Nano ,Cylinder ,Composite material ,Condensed Matter Physics ,Porosity ,Mathematical Physics ,Atomic and Molecular Physics, and Optics - Published
- 2021
- Full Text
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23. Soret and Dufour effects on thermosolutal convection developed in a salt gradient solar pond
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Fatima Bahraoui, Yassmine Rghif, and Belkacem Zeghmati
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Convection ,Finite volume method ,Materials science ,business.industry ,020209 energy ,Diffusion ,General Engineering ,02 engineering and technology ,Mechanics ,Condensed Matter Physics ,01 natural sciences ,Thermophoresis ,Dufour effect ,010305 fluids & plasmas ,Solar pond ,Mass transfer ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,business ,Thermal energy - Abstract
A numerical investigation of Soret and Dufour effects on heat and mass transfer in a Salt Gradient Solar Pond (SGSP) and its storage efficiency under meteorological conditions of Tangier (Morocco) is presented. This SGSP consists of an open square cavity filled with a saline solution. Its vertical and bottom walls are adiabatic and impermeable. Transfers are described by the Navier-Stokes, thermal energy and diffusion equations which are solved with a finite volume scheme and the Gauss method. The link between the pressure and velocity fields is carried out by the SIMPLE algorithm. The numerical model, developed in Fortran 95 language, is satisfactorily validated by comparisons with previously published numerical and experimental studies. Results show that the Dufour effect on thermosolutal convection in a SGSP is more relevant than the Soret effect. Nevertheless, increasing the value of the Dufour coefficient from 0 to 0.8 improves heat and mass transfer in the SGSP. Therefore, the amount of the thermal energy accumulated in the storage zone is reduced by about 5.56 %. In addition, the heat losses through the SGSP free surface are improved by around 8.53 %. more...
- Published
- 2021
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24. Bifurcation analysis of coupling thermosolutal convection induced by a thermal and solutal source in a horizontal cavity
- Author
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Mo Yang, Yubing Li, and Yuwen Zhang
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Physics ,Convection ,Buoyancy ,General Chemical Engineering ,Mechanics ,engineering.material ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Vortex ,Physics::Fluid Dynamics ,symbols.namesake ,Thermal ,engineering ,symbols ,Streamlines, streaklines, and pathlines ,Rayleigh scattering ,SIMPLE algorithm ,Bifurcation - Abstract
In this study, the bifurcation phenomenon and the existence of dual asymmetry solutions of double-diffusive convection driven by an internal thermal and solutal source in a horizontal cavity have been investigated systematically. The problem is solved by the SIMPLE algorithm with the QUICK scheme in a non-uniform staggered grid system. The Rayleigh numbers, 200 ≤ Ra ≤ 106, buoyancy ratios, −20 ≤ Nc ≤ 20, Soret numbers, 0 ≤ Sr ≤ 0.8, and Dufour numbers, 0 ≤ Df ≤ 0.8, are considered in this study. Different streamlines for the onset and evolution of static bifurcation are tracked. The paper aims to determine the critical Rayleigh numbers and buoyancy ratios for the onset of symmetry-breaking through bifurcation diagrams based on the vortex length. The results indicate that increasing buoyancy can destabilize the symmetric system. The strong couple diffusion effect delays the onset of bifurcation flow. A pair of asymmetric modes can be obtained under different initial conditions. more...
- Published
- 2021
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25. Three-dimensional numerical investigation on thermosolutal convection of power-law fluids in anisotropic porous media
- Author
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Q.Y. Zhu, Yijie Zhuang, and H.Z. Yu
- Subjects
Fluid Flow and Transfer Processes ,Convection ,Buoyancy ,Materials science ,Natural convection ,Mechanical Engineering ,Thermodynamics ,02 engineering and technology ,Rayleigh number ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Nusselt number ,010305 fluids & plasmas ,Physics::Fluid Dynamics ,Mass transfer ,0103 physical sciences ,engineering ,0210 nano-technology ,Porous medium ,Double diffusive convection - Abstract
The present study simulates the 3D unsteady double-diffusive natural convection subject to opposing thermal and solutal buoyancy forces (N
- Published
- 2017
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26. A model of coupled thermosolutal convection and thermoelasticity in soft rocks with consideration of water vapor absorption
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Yaoqin Chen, Q.Y. Zhu, and Yu Huaizhong
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Fluid Flow and Transfer Processes ,Convection ,Buoyancy ,Materials science ,Convective heat transfer ,020209 energy ,Mechanical Engineering ,0211 other engineering and technologies ,Thermodynamics ,02 engineering and technology ,Rayleigh number ,engineering.material ,Condensed Matter Physics ,Nusselt number ,Physics::Geophysics ,Physics::Fluid Dynamics ,Permeability (earth sciences) ,Thermal ,0202 electrical engineering, electronic engineering, information engineering ,engineering ,Streamlines, streaklines, and pathlines ,021101 geological & geomatics engineering - Abstract
The unsteady double-diffusive natural convection flow in a rectangular enclosure filled with soft rocks which are subjected to humid air, including water vapor absorption and thermoelasticity, is studied numerically. The high order compact finite difference schemes are adopted for better simulation of this problem, and a Darcy–Brinkman–Forchheimer extended model combined with the absorption and thermoelasticity effects is introduced. The effects of the thermal and solutal Rayleigh numbers, hygroscopicity, Darcy numbers and thermoelasticity on the flow are investigated in detail. Results are presented in the form of streamlines and isolines of temperature and mass fraction as well as the plots of average Nusselt and Sherwood numbers over the walls under different conditions. The flow structure develops from conduction-dominated to steady convection-dominated as increasing Rayleigh number or increasing buoyancy ratio as well as increasing Darcy numbers. The thermoelasticity effects of soft rocks play an important role in the analysis of thermal convection flow by the change of temperature and permeability, while the water vapor absorption effects may have a slight effect on the flow in the beginning and vanish with the absorption effects becoming weak. Nevertheless, the effect may significant reduce the mechanical strength properties of soft rocks. more...
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- 2016
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27. The energy stability of Darcy thermosolutal convection with reaction
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Bushra Al-Sulaimi
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Fluid Flow and Transfer Processes ,Darcy model ,Convection ,Materials science ,Mechanical Engineering ,Thermodynamics ,Condensed Matter Physics ,Instability ,Physics::Fluid Dynamics ,symbols.namesake ,Nonlinear system ,Energy stability ,symbols ,Energy method ,Rayleigh scattering ,Porous medium - Abstract
Thermosolutal convection with reaction in a porous media of Darcy type is studied using the energy method. The effect of the reaction terms on the temperature and salt Rayleigh numbers are presented graphically. Furthermore, nonlinear energy stability boundaries for different values of the reaction terms are compared with the linear instability boundaries obtained by Pritchard and Richardson (2007). more...
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- 2015
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28. Effects of Radiation Heat Transfer on Entropy Generation at Thermosolutal Convection in a Square Cavity Subjected to a Magnetic Field
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Ammar Ben Brahim, Mounir Bouabid, Nejib Hidouri, and Mourad Magherbi
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Convection ,Physics ,Buoyancy ,Natural convection ,Condensed matter physics ,square cavity ,Grashof number ,entropy generation ,General Physics and Astronomy ,lcsh:Astrophysics ,Laminar flow ,engineering.material ,magnetic effect ,radiation parameter ,lcsh:QC1-999 ,Magnetic field ,Physics::Fluid Dynamics ,thermosolutal convection ,lcsh:QB460-466 ,Heat transfer ,engineering ,lcsh:Q ,lcsh:Science ,Adiabatic process ,lcsh:Physics - Abstract
Thermosolutal convection in a square cavity filled with a binary perfect gas mixture and submitted to an oriented magnetic field taking into account the effect of radiation heat transfer is numerically investigated. The cavity is heated and cooled along the active walls whereas the two other walls are adiabatic and insulated. Entropy generation due to heat and mass transfer, fluid friction and magnetic effect has been determined for laminar flow by solving numerically: The continuity, momentum energy and mass balance equations, using a Control Volume Finite-Element Method. The structure of the studied flows depends on five dimensionless parameters which are: The Grashof number, the buoyancy ratio, the Hartman number, the inclination angle of the magnetic field and the radiation parameter. more...
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- 2011
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29. Acceleration of phase-field lattice Boltzmann simulation of dendrite growth with thermosolutal convection by the multi-GPUs parallel computation with multiple mesh and time step method
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Takayuki Aoki, Tomohiro Takaki, Yasushi Shibuta, Munekazu Ohno, and Shinji Sakane
- Subjects
010302 applied physics ,Convection ,Materials science ,Field (physics) ,Computation ,Lattice Boltzmann methods ,02 engineering and technology ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Computer Science Applications ,Acceleration ,Dendrite (crystal) ,Mechanics of Materials ,Modeling and Simulation ,0103 physical sciences ,Fluid dynamics ,General Materials Science ,0210 nano-technology ,Scaling ,ComputingMethodologies_COMPUTERGRAPHICS - Abstract
Thermosolutal convection inevitably occurs during the solidification of alloys owing to the nonuniform distribution of temperature and/or solute concentration, and this can drastically alter the resulting solidification microstructures. In this study, we present a large-scale simulation scheme for the phase-field lattice Boltzmann model, which can express dendrite growth upon considering the solute, heat transport, and liquid flow. A multiple mesh and time step method was employed to reduce computational costs, where different mesh sizes and time steps are used to solve the phase-field equation, the advection–diffusion equations of heat and solute, and the lattice Boltzmann equations for fluid flow. Furthermore, we implemented parallel computations using multiple graphics processing units (GPUs) to accelerate the large-scale simulation. Through the application of the multiple mesh and time step method, the computation was accelerated by approximately one hundred times compared to the case using a constant mesh and time step for all equations. Moreover, we confirmed that the developed parallel-GPU computation combined with the multiple mesh and time step method could achieve good acceleration and scaling through increasing the number of GPUs. We also confirmed that the developed method could simulate multiple dendrite growth with thermosolutal convection. more...
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- 2019
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30. Thermosolutal convection in an evolving soluble porous medium
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David M. Pritchard and Lindsey T. Corson
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Convection ,Natural convection ,Materials science ,Mechanical Engineering ,Thermodynamics ,Rayleigh number ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Mechanics of Materials ,Combined forced and natural convection ,0103 physical sciences ,TJ ,010306 general physics ,Porous medium ,Rayleigh–Bénard convection ,Convection cell ,Double diffusive convection - Abstract
We describe a mathematical model of double-diffusive (thermosolutal) convection in a saturated porous layer, when the solubility of the solute depends on the temperature, and the porosity and permeability of the porous medium evolve through dissolution and precipitation. We present the results of linear and weakly nonlinear stability analyses and explore the longer-term development of the system numerically. When the solutal concentration gradient is destabilising, the dynamics are somewhat similar to those previously found for single-species convection (Ritchie & Pritchard, J. Fluid Mech., vol. 673, 2011, pp. 286–317), including the occurrence of subcritical instabilities driven by a reaction–diffusion mechanism. However, when the solutal concentration gradient is stabilising and the thermal gradient is destabilising, novel dynamics emerge. These include a vertical segregation of circulation cells and porosity perturbations near the onset of convection, and over longer time scales the formation of a low-permeability region in the middle of the layer, pierced by occasional high-permeability channels. Under these conditions, convection may die away to nearly zero for extended periods before resuming vigorously in localised regions at later times. more...
- Published
- 2017
31. Thermosolutal convection within a vertical porous enclosure in the case of a buoyancy ratio balancing the separation parameter
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M. El Ganaoui, Abdelkhalk Amahmid, M. Er-Raki, Mohammed Hasnaoui, Faculté des Sciences Semlalia [Marrakech], Université Cadi Ayyad [Marrakech] (UCA), Axe 2 : procédés de traitements de surface, Science des Procédés Céramiques et de Traitements de Surface (SPCTS), Université de Limoges (UNILIM)-Ecole Nationale Supérieure de Céramique Industrielle (ENSCI)-Institut des Procédés Appliqués aux Matériaux (IPAM), Université de Limoges (UNILIM)-Université de Limoges (UNILIM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Limoges (UNILIM)-Ecole Nationale Supérieure de Céramique Industrielle (ENSCI)-Institut des Procédés Appliqués aux Matériaux (IPAM), and Université de Limoges (UNILIM)-Université de Limoges (UNILIM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS) more...
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Convection ,Mass flux ,Materials science ,Buoyancy ,Thermosolutal convection ,General Engineering ,Thermodynamics ,Porous medium ,02 engineering and technology ,Mechanics ,Soret effect ,engineering.material ,Analytical and numerical solution ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Boundary layer thickness ,Sherwood number ,Nusselt number ,Boundary layer ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Heat transfer ,engineering ,0210 nano-technology - Abstract
International audience; The present work deals with an analytical solution based on the parallel flow assumption obtained in the case of a vertical porous layer heated and salted from the long vertical sides with uniform fluxes of heat and mass, respectively. The study concerns a specific case for which the buoyancy ratio and the separation coefficient are identical. For this particular situation, the external mass flux is compensated by the Soret effect, which leads to zero concentration gradient on the vertical walls. The problem is first analyzed by solving numerically the full governing equations and the aspect ratio required to satisfy numerically the parallel flow conditions is determined. Analytical solutions for the pseudo-conductive and boundary layer regimes are proposed and discussed. The N-Le plane is divided into regions with specific behaviors and the results obtained are presented in terms of boundary layer thickness, heat transfer (Nusselt number), and mass transfer (Sherwood number) versus the main governing parameters. more...
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- 2009
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32. Stability analysis of thermosolutal convection in a horizontal porous layer using a thermal non-equilibrium model
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Shaowei Wang, Jianjun Tao, Wenchang Tan, and Xi Chen
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Fluid Flow and Transfer Processes ,Convection ,Materials science ,Natural convection ,Mechanical Engineering ,Thermodynamics ,Rayleigh number ,Heat transfer coefficient ,Condensed Matter Physics ,Nusselt number ,Physics::Fluid Dynamics ,Combined forced and natural convection ,Heat transfer ,Double diffusive convection - Abstract
A stability analysis is carried out to investigate the onset of thermosolutal convection in a horizontal porous layer when the solid and fluid phases are not in a local thermal equilibrium, and the solubility of the dissolved component depends on temperature. To study how the reaction and thermal non-equilibrium affect the double-diffusive convection, the effects of scaled inter-phase heat transfer coefficient H and dimensionless reaction rate k on thermosolutal convection are discussed . The critical Rayleigh number and the corresponding wave number for the stability and overstability convections are obtained. Specially, asymptotic analysis for both small and large values of H and k is presented, and the corresponding asymptotic solutions are compared with numerical results. At last, a nonlinear stability analysis is presented to study how H and k affect the Nusselt number. more...
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- 2011
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33. Thermosolutal convection in a fluid-porous composite medium
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Amitava Sarkar, Sofen K. Jena, and S.K. Mahapatra
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Fluid Flow and Transfer Processes ,Convection ,Temperature gradient ,Materials science ,Computer simulation ,Flow (psychology) ,Composite number ,Thermodynamics ,Mechanics ,Condensed Matter Physics ,Porous medium ,Adiabatic process ,Control volume - Abstract
In the present study analysis has been performed for thermosolutal convection in a fluid-porous composite medium, consisting of a fluid-saturated porous medium followed by an overlaying clean medium. The fluid-porous composite medium is subjected to both a horizontal solutal and a thermal gradient. Top and bottom walls of the fluid-porous composite medium are assumed to be impermeable and adiabatic. The Darcy-Brinkman-Forchheimer model is used to study the flow through the fluid-porous composite medium. A single domain approach is taken into consideration for numerical simulation. The solution is done by control volume integration. A comprehensive analysis has been performed for various pertinent parameters to delineate their behavior. Results of the transport phenomenon have been provided in graphical and tabular form, for the complete understanding of the complex phenomenon. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21048 more...
- Published
- 2013
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34. Transient Thermosolutal Convection of Boussinesq Fluid with Moving Heating and Cooling Blocks in a Square Cavity
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Mohammad Zoynal Abedin, Jinho Lee, P. Kandaswamy, Jung Bae Yoon, and Kyoung Jin Seong
- Subjects
Convection ,Numerical Analysis ,Materials science ,Buoyancy ,Stratification (water) ,Thermodynamics ,Square cavity ,Mechanics ,engineering.material ,Condensed Matter Physics ,Nusselt number ,Physics::Fluid Dynamics ,Thermal ,Vertical gradient ,engineering - Abstract
Transient thermosolutal convection of Boussinesq fluid with moving heating and cooling blocks placed at the bottom wall in a square cavity was numerically investigated subject to vertical gradient of thermosolutal conditions at the top or bottom walls. With the progress in time, due to the interactions among thermal and solutal buoyancy and stratification together with forced block movement, a complex flow structure was formed in the cavity as well as the corresponding transient heat and mass transports. At steady state, the absolute values of average Nusselt and Sherwood numbers remained almost constant with time as an increase of the velocity of the blocks. Furthermore, the cooling phase took more time than heating phase to reach the steady state, and time to reach the steady state decreased as an increase in the moving velocity of the block. more...
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- 2012
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35. Thermosolutal convection and solute segregation during the vertical Bridgman growth of Hg1−xCdxTe single crystals
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Bai Bofeng and Lu Jun
- Subjects
Convection ,Convective heat transfer ,Chemistry ,Flow (psychology) ,Thermodynamics ,Absolute value ,Rayleigh number ,Condensed Matter Physics ,Physics::Fluid Dynamics ,Inorganic Chemistry ,Thermal ,Materials Chemistry ,Coupling (piping) ,Bridgman growth - Abstract
The mechanism for thermosolutal convection and the coupling effects of flow, temperature and solute fields during the vertical Bridgman growth of Hg1−xCdxTe single crystals have been numerically analyzed. The calculations take into account the thermophysical properties and their dependence on temperature and composition. The results show that there are two main thermal convection cells in the melt caused by two temperature gradients during the growth of Hg1−xCdxTe single crystals. The stabilizing axial solute gradient in the melt will significantly damp the thermal convection cells when the absolute value of the solute Rayleigh number is close to the value of the thermal Rayleigh number. When there is a large solute gradient in the melt, the thermosolutal convection will become unstable, and the upper flow cell will evolve into a two-cell flow pattern. During the growth of Hg1−xCdxTe single crystals, the radial solute segregation in the melt develops non-monotonically with two minima values. Thus, the methods that solely aim at either damping or enhancing the thermosolutal convection are not always able to improve the radial solute segregation. more...
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- 2008
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36. 3D Thermosolutal Convection within Porous Media
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Elcafsi Afif, Rachid Bennacer, Kacem Amel, and Oueslati Fakhreddine
- Subjects
Convection ,Radiation ,Natural convection ,Convective heat transfer ,Chemistry ,Combined forced and natural convection ,Mass transfer ,Heat transfer ,Thermodynamics ,General Materials Science ,Condensed Matter Physics ,Adiabatic process ,Porous medium - Abstract
The present work aims to study convection and heat transfer and mass in a porous cubic cavity. The configuration considered is a cavity cube with vertical walls left and right are subjected to temperatures required while others are impermeable and adiabatic. We realized that the results depend on several characteristic parameters, and general correlations are established for the calculation of heat and mass transfer, according to various studied parameters. The study focuses on the influence of the control parameters on the structure of the flow, heat and mass transfer. more...
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- 2014
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37. Effect of Coriolis force on the thermosolutal convection threshold in a rotating annular Hele-Shaw cell
- Author
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S. Aniss and K. Souhar
- Subjects
Fluid Flow and Transfer Processes ,Convection ,Physics ,Prandtl number ,Fluid layer ,Mechanics ,Condensed Matter Physics ,Curvature ,Physics::Fluid Dynamics ,symbols.namesake ,Hele-Shaw flow ,Combined forced and natural convection ,Linear stability analysis ,symbols ,Nonlinear Sciences::Pattern Formation and Solitons - Abstract
In this study, the linear stability analysis is used to determine the onset of thermosolutal convection in fluids confined in rotating annular Hele-Shaw cell. The fluid layer is submitted to radial gradients of temperature and concentration. The effects of both Coriolis force and curvature parameter on the stationary and oscillatory convection are investigated when the Prandtl number is of the order of unity or larger than unity. more...
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- 2011
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38. Interaction of Participating Medium Radiation with Thermosolutal Convection-A Critical Appraisal
- Author
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Amitava Sarkar, Sofen K. Jena, and S.K. Mahapatra
- Subjects
Fluid Flow and Transfer Processes ,Physics ,Convection ,Buoyancy ,Opacity ,business.industry ,Upwind scheme ,Mechanics ,engineering.material ,Condensed Matter Physics ,Physics::Fluid Dynamics ,Optics ,Thermal radiation ,Heat transfer ,Emissivity ,engineering ,business ,Double diffusive convection - Abstract
The present study addresses the interaction effect of participating media radiation with the onset of double-diffusive convection in a square enclosure. Vertical walls are imposed with constant temperature and concentration, and the horizontal walls are impermeable and adiabatic. The boundaries of the enclosure are diffuse-gray, and the enclosed fluid isotropically scatters, emits, and absorbs thermal radiation. Numerical simulations have been performed for both aiding and opposing buoyancy conditions. The buoyancy ratio has been varied to simulate the effect of buoyancy driven flow and compositionally driven flow, along with transition of flow between the above. Optical properties like opacity of medium, scattering albedo, Planck number, and wall emissivity have been varied to depict their influence on flow and heat transfer. The modified MAC method is used for the solution of convective transport equations. Gradient dependent consistent hybrid upwind scheme of second order (GDCHUSSO) is used for the discretization of the convective terms. The discrete ordinate method, with S8 approximation, is used to solve the radiative transport equation. The parametric results are provided in graphical and tabular form. Flow lines, isotherms, and isoconcentration contour maps are provided to bring clarity in the understanding of the momentum, heat, and solute transport phenomenon. The stabilization effect of thermal radiation at critical buoyancy ratio for buoyancy opposed flow is observed. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21108 more...
- Published
- 2013
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39. Anisotropic inertia effect in microfluidic porous thermosolutal convection
- Author
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Brian Straughan
- Subjects
Convection ,Chemistry ,media_common.quotation_subject ,Microfluidics ,Rayleigh number ,Mechanics ,Condensed Matter Physics ,Inertia ,Instability ,Electronic, Optical and Magnetic Materials ,Physics::Fluid Dynamics ,Classical mechanics ,Thermal ,Materials Chemistry ,Anisotropy ,Porosity ,media_common - Abstract
The effect of an anisotropic inertia coefficient in the Darcy equations is studied. How such anisotropy affects the critical Rayleigh number for the onset of convective motion in a porous layer with thermal and solutal effects is analyzed quantitatively. The mathematical analyses employed involve both linear instability techniques and the energy method for nonlinear stability. more...
- Published
- 2013
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40. Three-dimensional Simulation of Thermosolutal Convection and Macrosegregation in Steel Ingots
- Author
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Baicheng Liu, Houfa Shen, and Wensheng Li
- Subjects
Equiaxed crystals ,Convection ,Materials science ,Discretization ,Metallurgy ,Alloy ,Metals and Alloys ,Mechanics ,engineering.material ,Condensed Matter Physics ,Physics::Fluid Dynamics ,Permeability (earth sciences) ,Three dimensional simulation ,Materials Chemistry ,engineering ,Physical and Theoretical Chemistry ,Ingot ,Shrinkage - Abstract
Thermosolutal convection and macrosegregation formation during the solidification of steel ingots are numerically simulated in three dimensions. The simulation is based on a fully coupled model for mass, momentum, energy, and species conservation equations. The interdendritic flow in the mushy zone is governed by Darcy's law, and the permeability term is discretized using an interpolated liquid fraction method. The numerical results for a benchmark test of macrosegregation in a Pb-Sn alloy are compared with experimental data taken from the literature. The present model is applied to simulate the solidification of industrial steel ingots. Preliminary predictions are obtained, including the positive segregation in the hot top, and the conically shaped negative segregation zone at the bottom of the ingot. The predicted variation of the segregation ratio in carbon along the vertical centreline of an ingot is compared with measurements, and generally good agreement is observed. Future attention should be paid to the precision of prediction by considering complex solidification issues, such as the sedimentation of free equiaxed grains and the formation of shrinkage cavity. more...
- Published
- 2010
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41. Thermosolutal Convection in a Partly Multi-Layred Porous Annular Cavity
- Author
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K. Khenfer, Mouhamed Benzeghiba, and Salahs Chikh
- Subjects
Convection ,Radiation ,Materials science ,Composite number ,Thermodynamics ,Mechanics ,Condensed Matter Physics ,Homogeneous ,Heat transfer ,General Materials Science ,Fluid motion ,Porous layer ,Porosity ,Porous medium - Abstract
The present study analyzes numerically the mixed thermosolutal convection in a vertical partly porous annular cavity. The fluid motion in the porous matrix is described by the generalized Darcy-Brinkman-Forchheimer model. The results show that the composite porous layer tends to improve the heat transfer and moderately reduce the transfer of aqueous solution compared to the case of a homogeneous porous partition. This conclusion is valid for all characteristic values (Da, ) or the flow modes set up in the porous matrix. more...
- Published
- 2010
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42. Hall effect on thermosolutal convection of ferromagnetic fluids in porous medium
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A. K. Aggarwal and Suman Makhija
- Subjects
Convection ,Materials science ,Condensed matter physics ,Ferromagnetism ,Convective heat transfer ,Hall effect ,Permeability (electromagnetism) ,Thermal stability ,Geophysics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Porous medium ,Magnetic field - Abstract
The present study deals with effect of Hall currents on thermal convection of ferromagnetic fluids in porous medium. The combined effect of solute gradient, medium permeability, magnetic field and Hall currents on the thermal stability has been investigated. It is found that Hall currents destabilize the system. The magnetic field and solute gradient have stabilizing effect on the convection. The medium permeability has conditional effect on the stability. The principle of exchange of stabilities (PES) is not satisfied under these conditions. In the absence of magnetic field and solute gradient, PES is valid. more...
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- 2017
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43. Thermosolutal Convection in An Annular Enclosure with Steps
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Y. C. Kung, Y. S. Chen, L. W. Wang, M. F. Kang, and F. C. Hsu
- Subjects
Convection ,Materials science ,Optics ,business.industry ,Applied Mathematics ,Mechanical Engineering ,Enclosure ,Mechanics ,Condensed Matter Physics ,business - Abstract
This study attempts to examine convection caused by the combined effects of temperature and concentration gradients in an annular enclosure with steps. An experimental study of thermosolutal convection of a CuSO4+ H2SO4+ H2O solution in a horizontal annular enclosure with steps is conducted using an electrochemical system that enables either opposing or cooperating in temperature and concentration gradients to be imposed. The shadowgraph recording technique is utilized to visualize and analyze the flow field phenomenon. The large difference between the thermal and solutal diffusion rates causes the flow to exhibit double-diffusive characteristics. In both cooperating and opposing cases, some finger-type flow can be visualized in the layered flow structure. Furthermore, Sh (mass transfer rate) increased with increasing Grt for fixed Grm and S*. Sh is larger in the cooperating case than in the opposing case for given Grt and Grm values. more...
- Published
- 2009
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44. Thermosolutal Convection During Melting in a Porous Medium Saturated with Aqueous Solution
- Author
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Fakhreddine S. Oueslati, Rachid Bennacer, A. Belghith, and Habib Sammouda
- Subjects
Physics::Fluid Dynamics ,Convection ,Numerical Analysis ,Nonlinear approximation ,Nonlinear system ,Materials science ,Aqueous solution ,Heat transfer ,Flow (psychology) ,Thermodynamics ,Condensed Matter Physics ,Flow show ,Porous medium - Abstract
The thermosolutal convection in a porous medium saturated with an aqueous solution near the temperature of the density maximum is studied. The fixed temperatures applied to vertical walls include the density maximum. The formulation of the problem is based on the Darcy-Brinkman model and the density variation is governed by a nonlinear approximation. The equations are solved by a finite-volume method. The numerical model is validated through experimental results. We show that the nonlinear variation of the density influences strongly the flow structure and the heat transfer. The structures of this flow show that the density maximum generates a complex flow structure of two contrarotating cells of unequal importance. more...
- Published
- 2008
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45. Effect of thermosolutal convection on microstructure formation in the Pb-Bi peritectic system
- Author
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Rohit Trivedi and Shan Liu
- Subjects
Convection ,Materials science ,Metallurgy ,Metals and Alloys ,Nucleation ,Thermodynamics ,Mineralogy ,Laminar flow ,Condensed Matter Physics ,Microstructure ,Boundary layer ,Mechanics of Materials ,Phase (matter) ,Metallic materials ,Phase matrix - Abstract
Experimental studies have been conducted in the two-phase region of the Pb-Bi peritectic system to investigate the effect of thermosolutal convection on the banded microstructure. A systematic study is carried out by varying convection effects through the use of thin cylindrical samples of different diameters. A strong oscillatory convection is found in a 6.0-mm-diameter sample that produces a large treelike primary phase in the center of the sample that is surrounded by the peritectic phase matrix. The length of the treelike structure is found to decrease as the diameter of a sample is reduced to 0.8 mm. When the sample diameter is further reduced to 0.4 mm, laminar flow is present that gives rise to discrete bands of the two phases. The banded microstructure, however, is found to be transient and only the peritectic phase forms after a few bands. Composition variations in the banded structure are measured to determine the nucleation undercoolings for both phases and to characterize the banding cycle. The banding cycle is determined by the nucleation undercoolings and is independent of convection in the melt, but the banding window closely depends on convection. The presence of the transient banding process is analyzed by using a boundary layer model, and the number of transient bands is found to agree with the model for samples of different compositions and lengths. more...
- Published
- 2006
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46. The effect of magnetic field dependent viscosity on thermosolutal convection in ferromagnetic fluid
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R. C. Sharma, Sunil, and Anupama
- Subjects
Convection ,Ferrofluid ,Materials science ,Condensed matter physics ,Applied Mathematics ,Thermodynamics ,Rayleigh number ,Instability ,Magnetic field ,Physics::Fluid Dynamics ,Computational Mathematics ,Magnetization ,Viscosity ,Thermal - Abstract
The effect of magnetic field dependent (MFD) viscosity on thermosolutal convection in ferromagnetic fluid is considered for a ferromagnetic fluid layer heated and soluted from below in the presence of a uniform vertical magnetic field. Using the linearized stability theory and the normal mode analysis method, an exact solution is obtained for the case of two free boundaries. For the case of stationary convection, stable solute gradient and MFD viscosity have stabilizing effects on the onset of instability. The magnetization may have destabilizing or stabilizing effect in the presence of MFD viscosity, whereas magnetization has always destabilizing effect in the absence of MFD viscosity. The critical wave number and critical magnetic thermal Rayleigh number for the onset of instability are also determined numerically for sufficiently large values of magnetic parameter M"1 and results are depicted graphically. The principle of exchange of stabilities is found to hold true for the ferromagnetic fluid heated from below in the absence of stable solute gradient. The oscillatory modes are introduced due to the presence of the stable solute gradient, which were non-existent in its absence. A sufficient condition for the non-existence of overstability is also obtained. more...
- Published
- 2005
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47. Soret effect on thermosolutal convection developed in a horizontal shallow porous layer salted from below and subject to cross fluxes of heat
- Author
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A. Amahmid, Mohammed Hasnaoui, and A. Mansour
- Subjects
Fluid Flow and Transfer Processes ,Convection ,Materials science ,Natural convection ,Heat flux ,Mechanical Engineering ,Mass transfer ,Heat transfer ,Thermodynamics ,Rayleigh number ,Condensed Matter Physics ,Lewis number ,Thermophoresis - Abstract
Combined effect of thermodiffusion and lateral heating on double diffusive natural convection in a horizontal porous layer, filled with a binary fluid and subjected to uniform fluxes of heat and mass on its long sides, is studied analytically and numerically. The short sides of the layer are impermeable to mass transfer and exposed to a perturbating constant heat flux. The governing parameters of problem under study are the Rayleigh number R T , the Lewis number Le , the buoyancy ratio N , the separation parameter φ , the ratio of the horizontal to vertical heat flux a and the aspect ratio A r of the layer. The thermodiffusion effect on the multiplicity of solutions is studied. It is demonstrated that the φ – N plane can be divided into four regions presenting different behaviors. The heat transfer is found to be considerably affected by the Soret effect. more...
- Published
- 2008
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48. Thermosolutal Convection in an Inclined Rectangular Enclosure with a Partition
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C. Y. Wu, Y. C. Kung, S. L. Wang, L. W. Wang, and M. F. Kang
- Subjects
Convection ,Physics ,Applied Mathematics ,Mechanical Engineering ,Partition (politics) ,Limiting current ,Enclosure ,Mechanics ,Condensed Matter Physics - Abstract
An experimental study of thermosolutal convection in an inclined rectangular enclosure with a partition is presented in this article. Aspect ratio, partition ratio, and inclination angle were kept constant at Ar =0.5, Ap = 0.25 and φ = 30°, respectively. The convective flow is generated by both inclined temperature and concentration gradients under limiting current condition. Both the thermal and solutal buoyancies, which either cooperated or opposed one another, were induced from the copper plates. The temperature gradient was maintained and controlled using two separate constant temperature baths that circulated heated or cooled water through a heat exchanger. We used copper sulphate-sulfuric acid solution as both the working fluid and the electrolyte. An electrochemical method based on a diffusion-controlled electrode reaction was employed to create the concentration gradient. We used the shadowgraph recording technique to visualize and analyze the flow field phenomenon. Thermal Grashof numbers ranging from 8.16 × 105 to 16.32 × 105 and a solutal Grashof number Grm = 4.36 × 106 were investigated. It is demonstrated that the mass transfer rate increases with the increasing thermal Grashof numbers within our experimental ranges. Multilayer structures are found in the cooperating case or the opposing case. more...
- Published
- 2004
- Full Text
- View/download PDF
49. Modeling of thermosolutal convection during Bridgman solidification of semiconductor alloys in relation with experiments
- Author
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Thierry Duffar and Carmen Stelian
- Subjects
Convection ,Momentum (technical analysis) ,Buoyancy ,Convective heat transfer ,Chemistry ,Alloy ,Mineralogy ,Thermodynamics ,engineering.material ,Condensed Matter Physics ,Inorganic Chemistry ,Materials Chemistry ,engineering ,Intensity (heat transfer) ,Directional solidification ,Rayleigh–Bénard convection - Abstract
Thermosolutal convection during vertical Bridgman directional solidification of Ga 1-x In x Sb alloys has been studied by numerical simulation. The transient analysis of heat, momentum and species transport has been performed by using the finite element code FIDAP R . In the case of vertical Bridgman configuration, the thermal convection is driven by the radial temperature gradients. The solute (InSb) rejected at the solid-liquid interface, which is heavier than the GaSb component, damps the thermally driven convection. The solutal effect on the melt convection has been analyzed for low (x = 0.01) and high (x = 0.1) doped Ga 1-x In x Sb alloys. It is found that the damping effect is negligible for Ga 0.99 In 0.01 Sb alloy grown at low pulling rates (V = 1 μm/s), but cannot be neglected if the pulling rate is increased. In the case of concentrated alloys, the low level of convection intensity leads to an increase of radial segregation and interface curvature during the whole growth process as also shown by experiments. The effect of solutal buoyancy force on the melt convection is analyzed for the horizontal Bridgman configuration under microgravity conditions. An inverse but lower solutal effect on the melt convection, as compared with vertical Bridgman arrangement, is observed. The results are in good agreement with the experimental data, and show that convective transport can be observed even for low (2 x 10 -6 g 0 ) residual gravity levels. more...
- Published
- 2004
- Full Text
- View/download PDF
50. Limitation of the 2D parallel flow assumption in thermosolutal convection: 2D-3D transition
- Author
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C. De Sa, Rachid Bennacer, K. Choukairy, Laboratoire de Mécanique, Université Hassan 1er [Settat], Laboratoire de Mécanique et Technologie (LMT), and École normale supérieure - Cachan (ENS Cachan)-Centre National de la Recherche Scientifique (CNRS) more...
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Physics ,Convection ,Convective heat transfer ,Enclosure ,Thermodynamics ,010103 numerical & computational mathematics ,Mechanics ,Condensed Matter Physics ,01 natural sciences ,Lewis number ,Computer Science Applications ,Physics::Fluid Dynamics ,[SPI]Engineering Sciences [physics] ,Mass transfer ,Heat transfer ,Fluid dynamics ,0101 mathematics ,Boussinesq approximation (water waves) ,ComputingMilieux_MISCELLANEOUS - Abstract
In this study, we investigated numerically two- and three-dimensional convective heat and mass transfer in a horizontal rectangular enclosure filled with heterogeneous porous media. The main goal is to underline the limitation of the widely used classical parallel flow assumption. The considered configuration is Cartesian. The horizontal and vertical walls are submitted to different mass and heat transfer. The Darcy model and the Boussinesq approximation are considered. The governing parameters which control the problem are the Darcy-Rayleigh number, Rt, the buoyancy ratio, N, the enclosure aspect ratio, A, the local permeability ratio, Kr and the Lewis number (fixed to ten in the present study). The obtained results with two-dimensional (2D) and three-dimensional (3D) approaches are compared to underline similarities and differences. We demonstrate the limit validity of 2D solution and the transition to 3D solutions when the convective forces or the domain permeable heterogeneity increases. The flow intensity, heat and mass transfer increases with the domain permeable heterogeneity. more...
- Published
- 2016
- Full Text
- View/download PDF
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