scholarly journals The fate of particles in a volumetrically heated convective fluid at high Prandtl number

2021 ◽  
Vol 929 ◽  
Author(s):  
Cyril Sturtz ◽  
Édouard Kaminski ◽  
Angela Limare ◽  
Stephen Tait
Keyword(s):  
Scaling Laws ◽  
Suspension Stability ◽  
Magma Chambers ◽  
Internal Heating ◽  
High Prandtl Number ◽  
Magma Oceans ◽  
The Stability ◽  
Lava Lakes ◽  
Convective Fluid ◽  
Key Parameter

The dynamics of suspensions plays a crucial role in the evolution of geophysical systems such as lava lakes, magma chambers and magma oceans. During their cooling and solidification, these magmatic bodies involve convective viscous fluids and dispersed solid crystals that can form either a cumulate or a floating lid by sedimentation. We study such systems based on internal heating convection experiments in high Prandtl fluids bearing plastic beads. We aim to determine the conditions required to produce a floating lid or a sedimented deposit. We show that, although the sign of particles buoyancy is the key parameter, it is not sufficient to predict the particles fate. To complement the model we introduce the Shields formalism and couple it with scaling laws describing convection. We propose a generalized Shields number that enables a self-consistent description of the fate of particles in the system, especially the possibility to segregate from the convective bulk. We provide a quantification of the partition of the mass of particles in the different potential reservoirs (bulk suspension, floating lid, settled cumulate) through reconciling the suspension stability framework with the Shields formalism. We illustrate the geophysical implications of the model by revisiting the problem of the stability of flotation crusts on solidifying rocky bodies.

scholarly journals Effect of Vadasz Number on Magnetoconvection in a Darcy Porous Layer with Concentration Based Internal Heating

2019 ◽  
pp. 1-13
Author(s):  
C. Israel-Cookey ◽  
L. Ebiwareme ◽  
E. Amos
Keyword(s):  
Magnetic Field ◽  
Rayleigh Number ◽  
Porous Layer ◽  
Internal Heat ◽  
Lewis Number ◽  
Mode Analysis ◽  
Internal Heating ◽  
Vadasz Number ◽  
The Stability ◽  
Solutal Rayleigh Number

In this research article, the effect of Vadasz number on magnetoconvection in a Darcy Porous Layer with concentration based internal heating is studied. The flow is governed by the Oberbeck-Boussineq model for Newtonian fluid. The stability analysis method based on the perturbation of infinitesimal amplitude is carried out using the normal mode analysis. The onset criterion for both the stationary and oscillatory convection on the stability of system is obtained. The analysis examines the effects of pertinent parameters on the stability of the system: magnetic field parameter, solutal Rayleigh number, Lewis number and Vadasz number. The result show that, internal heat parameter,  and Lewis number, , hastens the onset of instability in the system, whereas magnetic field, , Vadasz number,  and solutal Rayleigh number,  delay the onset of instability.

scholarly journals Improving stability of cerium oxide nanoparticles by microbial polysaccharides coating

2018 ◽  
Vol 83 (6) ◽  
pp. 745-757 ◽  
Author(s):  
Ivana Milenkovic ◽  
Ksenija Radotic ◽  
Branko Matovic ◽  
Marija Prekajski ◽  
Ljiljana Zivkovic ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cerium Oxide ◽  
Aqueous Media ◽  
Suspension Stability ◽  
X Ray Diffraction ◽  
Synthesis Conditions ◽  
Transmission Electron ◽  
Ft Ir ◽  
Microbial Exopolysaccharides ◽  
The Stability

Cerium oxide (CeO2) nanoparticles (CONPs) are interesting biomaterials with various applications in biomedicine, cosmetics and the pharmaceutical industry, but with limited practical application because of their low stability in aqueous media. The aim of this study was to obtain CONPs with increased stability by coating the particles. Microbial exopolysaccharides (levan, pullulan) and glucose were used to prepare CONPs under different synthesis conditions. Coating was attempted by adding the carbohydrates during (direct coating) or after (subsequent coating) the synthesis of CONPs. The obtained nanoparticles were characterized by X-Ray diffraction analysis, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The suspension stability of the uncoated and coated CONPs in aqueous media was evaluated by measuring the hydrodynamic size, zeta potential and turbidity. The FT-IR spectra revealed the differences between coated CONPs and showed the success of subsequent coating with carbohydrates. Coating with carbohydrates improved the stability the CONP suspension by decreasing the size of aggregated particles. The suspensions of levan- and glucose-coated CONPs had the best stability. In this study, CONPs were prepared using non-toxic materials, which were completely environmentally friendly. The obtained results open new horizons for CONP synthesis, improving their biological applications.

Effects of pH and surfactant on the forced convection of Al2O3/water and TiO2/water nanofluids

2020 ◽  
pp. 1-18
Author(s):  
Deepak Khurana ◽  
Sudhakar Subudhi
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Particle Concentration ◽  
Sodium Dodecyl ◽  
Suspension Stability ◽  
Heat Transfer Characteristics ◽  
Maximum Enhancement ◽  
Effects Of Ph ◽  
Set Up ◽  
The Stability

Abstract The present paper deals with the forced convection of Al2O3/water and TiO2/water nanofluids with the variation of pH and addition of surfactant in nanofluids. The aim of this study is to investigate the effect of suspension stability on the heat transfer and pressure drop characteristics of nanofluids. The present experimental set up is same as used by our earlier paper [1]. The suspension stability of nanofluids is improved by varying pH of nanofluids. The pH in this study is varied from 3.5±0.2 to 12.5±0.2. Addition of surfactants is employed to improve the suspension stability of nanofluids. The SDS (sodium dodecyl sulfate) surfactant of 0.05 wt % is used to increase the stability of nanofluids in the present study. It is observed that by increasing the suspension stability with the variation of pH and addition of surfactant, the heat transfer characteristics have improved appreciably. The maximum enhancement in heat transfer is obtained with TiO2/water nanofluids at a particle concentration of 0.1 vol % and a pH of 3.5±0.2.

Thermogelation of Composite Films Produced by Electrophoretic Codeposition

2006 ◽  
Vol 314 ◽  
pp. 63-68
Author(s):  
Begoña Ferrari ◽  
Isabel Santacruz ◽  
Isabel M. De Francisco ◽  
María Isabel Nieto ◽  
Rodrigo Moreno
Keyword(s):  
Composite Films ◽  
Rheological Behaviour ◽  
Processing Route ◽  
Layered Systems ◽  
Constant Rate ◽  
Shape Retention ◽  
Ceramic Suspensions ◽  
The Stability ◽  
Thick Coatings ◽  
Key Parameter

There is a growing interest to develop reliable, economic and environmentally-friendly methods for manufacturing thick coatings and layered systems. For thick films, the adhesion to the substrate and the shape retention become important problems that lead to low density, cracking, and heterogeneous surfaces. To overcome these problems, a processing route is proposed consisting in the formation of a thick deposit by EPD in water and its immediate consolidation by thermogelation of polysaccharides. The process is based on the use of aqueous suspensions containing low concentration of biopolymers (i.e. carrageenan) and the formation of the film by dipping and/or EPD on suspensions heated at 60°C. On withdrawal at constant rate a film is obtained after cooling at room conditions. Maintaining the stability of the hot suspensions and during gelation is a key parameter to produce controlled deposits with good adhesion to the substrate and uniform microstructure. In this work, ceramic suspensions or Ni-containing suspensions have been stabilized with acrylic-based polyelectrolytes at controlled pH. Self-supported films of Al2O3/Y-TZP have been produced by dipping and EPD on graphite substrates that are burnt out on heating. On the other hand, Ni/YSZ composites have been deposited on graphite to produce either monolithic or laminated films. The optimization of the rheological behaviour of the suspensions and the EPD kinetics allows manufacturing a variety of complex structures with layers having controlled thickness ranging from 10 to 200 6m.

scholarly journals Review on the recent progress in the preparation and stability of graphene-based nanofluids

2020 ◽  
Vol 142 (3) ◽  
pp. 1145-1172 ◽  
Author(s):  
Thong Le Ba ◽  
Omid Mahian ◽  
Somchai Wongwises ◽  
Imre Miklós Szilágyi
Keyword(s):  
Physical Properties ◽  
Surface Area ◽  
Heat Conductivity ◽  
Recent Progress ◽  
Research Work ◽  
Volume Ratio ◽  
Suspension Stability ◽  
Pumping Power ◽  
Erosion Corrosion ◽  
The Stability

Abstract Graphene has attracted much attention from the science world because of its mechanical, thermal, and physical properties. Graphene nanofluid is well known for its easy synthesis, longer suspension stability, higher heat conductivity, lower erosion, corrosion, larger surface area/volume ratio, and lower demand for pumping power. This article is an audit of experimental outcome about the preparation and stability of graphene-based nanofluids. Numerous researches to prepare and stabilize graphene-based nanofluids have been developed, and it is indispensable to create a complete list of the approaches. This research work outlines the advancement on preparation and assessment methods and the techniques to enhance the stability of graphene nanofluids and outlook prospects.

The Sedimentation Velocity of Erythrocytes in the Psychoses: a Study of Seventy-Three Cases

1929 ◽  
Vol 75 (308) ◽  
pp. 80-100 ◽  
Author(s):  
E. W. Anderson
Keyword(s):  
Physiological Condition ◽  
Sedimentation Velocity ◽  
Buffy Coat ◽  
Suspension Stability ◽  
Historical Survey ◽  
The Stability ◽  
Cellular Pathology ◽  
Morbid Conditions

At the outset it may be desirable to give a brief outline of the phenomena upon which this work is based.A complete historical survey takes us back to very early times, to the days of Hippocrates and in more recent times to the humoral pathologists, when the formation of the “crust phiogistica” or “buffy coat” was practically the only blood symptom known. Until the old humoral theories were discarded, that is until the rise of the doctrines of cellular pathology, the problem loomed large, but after this period interest in it declined, until the whole matter was revived about ten years ago by R. Fahraeus, of Stockholm, who published a series of researches into what he termed the “suspension stability” of the blood. By this term is meant the power which the plasma has of holding the erythrocytes in suspension. When the stability is lowered, the corpuscles sink with increased rapidity. This author found that a lowered suspension stability occurred in a large number of morbid conditions, and also in one physiological condition, namely pregnancy. Since the publication of this work the phenomenon in question has been made the basis of a test which has found considerable application in certain departments of medicine, notably in gynæcology and tuberculosis.

The Cylindrical Air Spring Suspension Stability Model and Simulation

2012 ◽  
Vol 201-202 ◽  
pp. 321-324
Author(s):  
Liang Wang ◽  
Chong Chen ◽  
De Jun Yang ◽  
Rong Rong Hu
Keyword(s):  
Original Data ◽  
Suspension Stability ◽  
Air Spring ◽  
Stability Performance ◽  
Model And Simulation ◽  
Spring Suspension ◽  
Stability Model ◽  
Close Relationship ◽  
The Stability ◽  
Real Vehicle

There is a close relationship between the stability of vehicle and the suspension. In this paper, an air spring suspension stability model is established by MATLAB/Simulink based on vehicle stability theories. This air spring suspension stability model is used to analyze the performance of air spring suspension and the stability of vehicle by the simulation of gyratory motion and linear motion, after that real vehicle tests is performed, the contrast between them will be used to judge the accuracy and effectiveness of the air spring suspension stability model. In this paper, some original data come from a sedan. The data of this paper has proved the vehicle installing the cylindrical air spring suspension, has a good stability performance.

A model for the onset of penetrative convection

1988 ◽  
Vol 188 ◽  
pp. 571-583 ◽  
Author(s):  
P. C. Matthews
Keyword(s):  
Deep Layer ◽  
Finite Depth ◽  
Internal Heating ◽  
Penetrative Convection ◽  
Weakly Nonlinear ◽  
Weakly Nonlinear Analysis ◽  
System A ◽  
The Difference ◽  
The Stability ◽  
Rayleigh Numbers

The stability of an S-shaped, cubic temperature profile, maintained by internal heating, is considered as a model for circumstances in which an unstably stratified layer of fluid is bounded by two stable layers. Critical Rayleigh numbers are computed for the cases of an infinitely deep layer, and for a layer of finite depth with symmetrically placed free or rigid boundaries. It is found that the introduction of boundaries can reduce the stability of the system. A weakly nonlinear analysis shows that the bifurcation is supercritical and that rolls are preferred to squares for all values of the Prandtl number. This result prompts a re-examination of the model of penetrative convection in water above ice, in which the bifurcation is subcritical, in order to understand the difference between the two models.

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