Initiation of underwater granular avalanches: Influence of the initial volume fraction

2008 ◽  
Vol 20 (11) ◽  
pp. 111701 ◽  
Author(s):  
M. Pailha ◽  
M. Nicolas ◽  
O. Pouliquen
Keyword(s):  
Volume Fraction ◽  
Initial Volume ◽  
Initial Volume Fraction

Compressive Yield Stress of Cement Paste

1994 ◽  
Vol 370 ◽  
Author(s):  
Kelly T. Miller ◽  
Wei Shi ◽  
Leslie J. Struble ◽  
Charles F. Zukoski
Keyword(s):  
Yield Stress ◽  
Calcium Aluminate ◽  
General Property ◽  
Volume Fraction ◽  
Initial Structure ◽  
Compressive Behavior ◽  
Initial Volume ◽  
Initial Volume Fraction ◽  
Compressive Yield Stress ◽  
Aluminate Cement

AbstractCompressive yield stresses have been measured for pastes (0.35 ≤ w/c ≤ 0.50) of portland cement, calcium aluminate cement, and weakly and strongly flocculated alumina (Φ0 = 0.20) using the centrifuge sediment height technique. Equilibrium sediment heights are reached quickly, allowing all measurements to be taken during the cement's induction period. The compressive behavior showed little dependence on the compressive history. Compressive yield stress was, however, dependent upon initial volume fraction, decreasing as the initial volume fraction increases. This behavior was observed in both the cements and alumina suspensions, implying that strong dependencies on initial structure may be a general property of the compressive behavior of flocculated suspensions.

Numerical Evaluation of Micro- to Macroscopic Mechanical Behavior of Plastic Foam

2007 ◽  
Vol 340-341 ◽  
pp. 1025-1030
Author(s):  
Isamu Riku ◽  
Koji Mimura
Keyword(s):  
Mechanical Behavior ◽  
Strain Hardening ◽  
Loading Condition ◽  
Volume Fraction ◽  
Plastic Foam ◽  
Uniform Compression ◽  
Initial Volume ◽  
Initial Volume Fraction ◽  
Characteristic Value ◽  
Initial Modulus

In this study, we employ the two-dimensional homogenization model based on molecular chain network theory to investigate the micro- to macroscopic mechanical behavior of plastic foam under macroscopic uniform compression. A parametric study is performed to quantify the effect of a characteristic value of matrix, distribution and initial volume fraction of voids, and the macroscopic triaxiality of loading condition on the deformation behavior of the foam. The results suggest that the onset of localized shear band at the ligament between voids together with the microscopic buckling of the ligament leads to the macroscopic yield of the foam. The initial modulus and the macroscopic yield stress of the foam have no dependence on the characteristic value of matrix. Furthermore, as the microscopic buckling of the ligament is promoted in case of high initial volume fraction of voids and high triaxiality loading condition, the macroscopic yield point appears at early deformation stage. After the macroscopic yield, macroscopic strain hardening appears in the macroscopic response and a remarkable strain hardening is shown in case of high initial volume fraction of voids and high triaxiality loading condition due to the considerable increase of the density of the foam in these cases.

Initiation of Submarine Granular Avalanches: Role of the Initial Volume Fraction

2008 ◽  
Author(s):  
Mickaël Pailha ◽  
Olivier Pouliquen ◽  
Maxime Nicolas ◽  
Albert Co ◽  
Gary L. Leal ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Initial Volume ◽  
Initial Volume Fraction

scholarly journals Granular collapse in a fluid: Role of the initial volume fraction

2011 ◽  
Vol 23 (7) ◽  
pp. 073301 ◽  
Author(s):  
L. Rondon ◽  
O. Pouliquen ◽  
P. Aussillous
Keyword(s):  
Volume Fraction ◽  
Initial Volume ◽  
Initial Volume Fraction ◽  
Granular Collapse

A two-phase flow description of the initiation of underwater granular avalanches

2009 ◽  
Vol 633 ◽  
pp. 115-135 ◽  
Author(s):  
MICKAËL PAILHA ◽  
OLIVIER POULIQUEN
Keyword(s):  
Critical State ◽  
Two Phase Flow ◽  
Volume Fraction ◽  
State Theory ◽  
Phase Flow ◽  
Two Phase ◽  
Initial Volume ◽  
Initial Volume Fraction ◽  
Critical State Theory

A theoretical model based on a depth-averaged version of two-phase flow equations is developed to describe the initiation of underwater granular avalanches. The rheology of the granular phase is based on a shear-rate-dependent critical state theory, which combines a critical state theory proposed by Roux & Radjai (1998), and a rheological model recently proposed for immersed granular flows. Using those phenomenological constitutive equations, the model is able to describe both the dilatancy effects experienced by the granular skeleton during the initial deformations and the rheology of wet granular media when the flow is fully developed. Numerical solutions of the two-phase flow model are computed in the case of a uniform layer of granular material fully immersed in a liquid and suddenly inclined from horizontal. The predictions are quantitatively compared with experiments by Pailha, Nicolas & Pouliquen (2008), who have studied the role of the initial volume fraction on the dynamics of underwater granular avalanches. Once the rheology is calibrated using steady-state regimes, the model correctly predicts the complex transient dynamics observed in the experiments and the crucial role of the initial volume fraction. Quantitative predictions are obtained for the triggering time of the avalanche, for the acceleration of the layer and for the pore pressure.

Effect of Brownian and Thermophoretic Diffusions of Nanoparticles on Nonequilibrium Heat Conduction in Nanofluids

2008 ◽  
Author(s):  
Yuwen Zhang ◽  
Ling Li ◽  
H. B. Ma
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Initial Temperature ◽  
Volume Fraction ◽  
Density Ratio ◽  
Lewis Number ◽  
Soret Coefficient ◽  
Transfer Enhancement ◽  
Initial Volume Fraction ◽  
Periodic Heat

Effects of Brownian and thermophoretic diffusions on nonequilibrium heat conduction in a nanofluid layer with periodic heat flux on one side and specified temperature on the other side are investigated numerically. The problem are described by eight dimensionless parameters: density ratio, heat capacity ratio, Lewis number, Soret coefficient, initial volume fraction of nanoparticles, initial temperature, Sparrow number, and period of the surface heat flux. Effects of Brownian and thermophoretic diffusions of nanoparticles on nonequilibrium heat conduction in nanofluid obtained by dispersing copper nanoparticles into ethylene glycol are investigated. The results showed that the Brownian and thermophoretic diffusions only affect the nanoparticle temperature but their effect on the heat transfer enhancement is negligible.

scholarly journals Granular Stack Density’s Influence on Homogeneous Fluidization Regime: Numerical Study Based on EDEM-CFD Coupling

2021 ◽  
Vol 11 (18) ◽  
pp. 8696
Author(s):  
Aboubacar Sidiki Drame ◽  
Li Wang ◽  
Yanping Zhang
Keyword(s):  
Volume Fraction ◽  
Numerical Study ◽  
Initial Density ◽  
Strong Impact ◽  
Fast Kinetics ◽  
Bed Height ◽  
Initial Volume Fraction ◽  
Fluidization Regime ◽  
Original Observation ◽  
Initial Packing

FLUENT and EDEM were applied to simulate liquid–solid coupling in a 3D homogenous fluidization. The dynamics of destabilization of the granular material immersed by homogeneous fluidization were observed. The effect of initial packing density of granular stack and fluidization rate on the fluidization’s transient regime, the configuration of particles in the fluidized bed and the variation of bed height were analyzed and discussed. According to the results, there was an original observation of a strong impact of the initial density of an initially static granular stack on the transient fluidization regime. Depending on the material initial volume fraction, there was a difference in grain dynamics. For an initially loose stack, a homogeneous turbulent fluidization was observed, whereas for an initially dense stack, there was a mass takeoff of the stack. The propagation of wave porosity instability, from the bottom to the top of the stack with fast kinetics that decompacted the medium, followed this mass takeoff.

TiC plasma spray cermets

2020 ◽  
pp. 65-74
Author(s):  
V. I. Kalita ◽  
◽  
A. A. Radyuk ◽  
D. I. Komlev ◽  
A. B. Mikhailova ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Plasma Spray ◽  
Volume Fraction ◽  
Liquid Phase Sintering ◽  
Subsequent Formation ◽  
Initial Volume Fraction ◽  
The Matrix ◽  
High Microhardness ◽  
Reduction Of Oxides ◽  
Additional Hardening

The microstructure and microhardness of eleven volumetric cermets based on TiC carbide with nickel and cobalt based matrices after liquid-phase sintering at a temperature of 1400 °C were studied. It is supposed to use the research results for the subsequent formation of a powder for plasma spraying of coatings. The compositions of the matrix, additional hardening phases, and carbon were selected taking into account the specific features of the formation of plasma coatings: a decrease in the carbon content and high solidification rates of the sprayed particles with the formation of additional nanosized carbides and an increase in the volume fraction of carbides from 70 % to 88 %. As the matrix, we used the traditional composition for cermets with TiC carbide, NiCr – Mo,  and industrial powders, PGSR brands, Ni – 13.5 Cr – 2.7 Si – 4.5 Fe – 0.37 C – 1.65 B, and TAFA 1241F Co – 32 Ni – 21 Cr – 8  Al – 0.5 Y. The ring zone on TiC carbide is formed with the participation of WC, Cr3C2, TiN, matrix phases and additional carbon in the composition of cermets, 1 – 2.8 %, as a result, the initial volume fraction of TiC carbide increases 70 to 88 %. Additional carbon is consumed to reduce oxygen content at the stage of sintering (reduction of oxides). After sintering, cermets have high microhardness values at a load on an indenter of 20 G, 1940 – 3210 kgf/mm2, and lower values at a load on an indenter of 200  G, which was explained by a scale factor. The maximum calculated contribution of the hardness of the hardening phases to the hardness of the cermet was established for cermets with a Co matrix of 3681 kgf/mm2.

scholarly journals Particle Deposition in Drying Porous Media

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5120
Author(s):  
Emmanuel Keita
Keyword(s):  
Porous Media ◽  
Liquid Flow ◽  
Particle Deposition ◽  
Building Materials ◽  
Volume Fraction ◽  
Solid Matrix ◽  
X Ray ◽  
Initial Volume Fraction ◽  
Solid Deposit ◽  
Nanoparticle Suspensions

The drying of porous media is a ubiquitous phenomenon in soils and building materials. The fluid often contains suspended particles. Particle deposition may modify significantly the final material, as it could be pollutants or clogging the pores, decreasing the porosity, such as in salt, in which particles and drying kinetics are coupled. Here, we used SEM and X-ray microtomography to investigate the dried porous media initially saturated by nanoparticle suspensions. As the suspensions were dried, nanoparticles formed a solid deposit, which added to the initial solid matrix and decreased the porosity. We demonstrate that since the drying occurred through the top surface, the deposit is not uniform as a function of depth. Indeed, the particles were advected by the liquid flow toward the evaporative surface; the deposit was significant over a depth that depended on the initial volume fraction, but the pore size was affected over a very narrow length. These findings were interpreted in the frame of a physical model. This study may help to design better porous media and take into account particle influence in drying processes.

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