The motion of solid particles suspended in viscoelastic liquids under torsional shear

1996 ◽  
Vol 324 ◽  
pp. 199-222 ◽  
Author(s):  
J. Feng ◽  
D. D. Joseph
Keyword(s):  
Flow Direction ◽  
Particle Interaction ◽  
Radial Force ◽  
Solid Particles ◽  
Small Amplitude Oscillatory Shear ◽  
Radial Migration ◽  
Local Shear ◽  
Change Of Type ◽  
Torsional Flow ◽  
And Migration

This paper presents an experimental study of the behaviour of single particles and suspensions in polymer solutions in a torsional flow. Four issues are investigated in detail: the radial migration of a shperical particle; the rotation and migration of a cylindrical particle; the particle-particle interaction and microstructures in a suspension of spheres; and the microstructures in a suspension of rods. Newtonian fluids are also tested under similar flow conditions for comparison. A spherical particle migrates outward at constant velocity unless the polymer solution is very dilute. A rod in a viscoelastic fluid has two modes of motion depending on its initial orientation, aspect ratio, the local shear rate and the magnitude of normal stresses in the fluid. In the first mode, the rod rotates along a Jeffery-like orbit around the local vorticity axis. It also migrates slowly inward. The second mode of motion has the rod aligned with the local stream at all times; the radial migration is outward. A hypothesis proposed by Highgate & Whorlow (1968) on the radial force on a particle in a cone-and-plate geometry is generalized to explain the variation of migration speed in torsional flows. Spheres form chains and aggregates when the suspension is sheared. The chains are along the flow direction and may connect to form circular rings; these rings migrate outward at a velocity much higher than that of a single sphere. Rods interact with one another and aggregate in much the same way, but to a lesser extent than spheres. It is argued that the particle interaction and aggregation are not direct results of the shear flow field. Two fundamental mechanisms discovered in sedimentation are applied to explain the formation of chains and aggregates. Finally, the competition between inertia and elasticity is discussed. A change of type is not observed in steady shear, but may happen in small-amplitude oscillatory shear.

scholarly journals Simulation of Flexible Fibre Particle Interaction with a Single Cylinder

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 191
Author(s):  
Naser Hamedi ◽  
Lars-Göran Westerberg
Keyword(s):  
Reynolds Number ◽  
Shear Flow ◽  
Fibre Orientation ◽  
Flow Direction ◽  
Particle Interaction ◽  
Orientation Angle ◽  
Factors Affecting ◽  
Single Cylinder ◽  
Flow Past ◽  
Fibre Suspension

In the present study, the flow of a fibre suspension in a channel containing a cylinder was numerically studied for a very low Reynolds number. Further, the model was validated against previous studies by observing the flexible fibres in the shear flow. The model was employed to simulate the rigid, semi-flexible, and fully flexible fibre particle in the flow past a single cylinder. Two different fibre lengths with various flexibilities were applied in the simulations, while the initial orientation angle to the flow direction was changed between 45° ≤ θ ≤ 75°. It was shown that the influence of the fibre orientation was more significant for the larger orientation angle. The results highlighted the influence of several factors affecting the fibre particle in the flow past the cylinder.

Simulation of Impaction Between Liquid Droplet and Solid Particles Based on SPH Method

2014 ◽  
Author(s):  
Shuai Meng ◽  
Qian Wang ◽  
Rui Yang
Keyword(s):  
Surface Tension ◽  
Solid Particle ◽  
Liquid Droplet ◽  
Particle Interaction ◽  
Solid Particles ◽  
Seed Particle ◽  
Liquid Droplets ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Spray Granulation

The phenomenon of impaction between liquid droplets and solid particles is involved in many scientific problems and engineering applications, such as impaction between sprayed droplet and solid particles in limestone injection desulfurization system and the collision between a droplet of the liquid to be granulated and a seed particle in fluidized bed spray granulation process. There are a lot of factors affected this phenomenon: droplet and particle size, momentum of both liquid droplet and solid particles, materials, surface conditions of the solid particles and so on. However the experimental or numerical researches have been done mostly pay attention to Specific application or process, so the impaction phenomenon has not been through studied, for example how different factors affected the impaction process with its effect on different applications. This paper focuses on the basic issue of interaction between droplet and solid particles. Three main factors were considered: ratio of diameter between the droplet and solid particle, relative velocity and the surface tension (including the contact angle between droplet and solid particle). All the study is based on simulation using SPH (smoothed particle hydrodynamics) method, and the surface tension is simulated by particle-particle interaction.

scholarly journals Detection of Gas-Solid Two-Phase Flow Based on CFD and Capacitance Method

2018 ◽  
Vol 8 (8) ◽  
pp. 1367 ◽  
Author(s):  
Wanting Zhou ◽  
Yue Jiang ◽  
Shi Liu ◽  
Qing Zhao ◽  
Teng Long ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Cfd Simulation ◽  
Fluid Model ◽  
Flow Direction ◽  
Solid Particles ◽  
Drilling Process ◽  
Sources Of Information ◽  
Discrete Phase Model ◽  
Horizontal Drilling ◽  
Annular Channels

Multiphase flow in annular channels is complex, particularly in the region where the flow direction abruptly changes between the inner pipe and the outer pipe, as the cases in horizontal drilling and pneumatic conveying. Simplified models and experience are still the main sources of information. First, to understand the process more deeply, Computational Fluid Dynamics (CFD) package Fluent is used to simulate the gas-solid flow in the horizontal and the inclined section of an annular pipe. Discrete Phase Model (DPM) is adopted to calculate the trajectories of solid particles of different sizes at different air velocities. Also, the Two-Fluid model is used to simulate the sand flow in the inclined section for the case of air flow stoppage, for which an experiment is also conducted to verify the CFD simulation. Simulation results reveal the behaviour of the solid particles showing the dispersed spatial distribution of small particles near the entrance. On the other hand, larger particles manifest a distinct sedimented flow pattern along the bottom of the pipe. The density distribution of the particles over a pipe cross section is demonstrated at a variety of air velocities. The results also show that the large airspeed tends to generate swirls near the outlet of the inner pipe. In addition, Electrical Capacitance Tomography (ECT) technology is used to reconstruct the spatial distribution of particles, and the cross-correlation algorithm to detect velocity. Both the distribution and the velocity measurement by electric sensors agree reasonably well with the CFD predictions. The details revealed by CFD simulation and the mutual-verification between CFD simulation and the ECT method of this study could be valuable for the industry in drilling process control and equipment development.

Migration of solid particles perpendicular to a local shear flow dueto local instabilities

AIAA Journal ◽  
1987 ◽  
Vol 25 (7) ◽  
pp. 1016-1018 ◽  
Author(s):  
M. Fichman ◽  
D. Pnueli
Keyword(s):  
Shear Flow ◽  
Solid Particles ◽  
Local Shear

LES of Particle-Laden Flow With Inter-Particle Collisions

2003 ◽  
Author(s):  
Mikhael Gorokhovski ◽  
Anna Chtab
Keyword(s):  
Gas Flow ◽  
Particle Interaction ◽  
Solid Particles ◽  
Particle Interactions ◽  
Particle Collisions ◽  
Cpu Time ◽  
Eddy Simulation ◽  
Preferential Concentration ◽  
Large Eddy ◽  
Particle Laden Flow

By analogy with kinetic approach, the gas-solid turbulent flow was considered as an ensemble of interacting both stochastic liquid and solid particles. In this way, the motion equation for the solid particle along a smoothed trajectory has been derived. To close this equation, the statistical temperature of particles has been introduced and expressed by statistical properties of turbulence. The smoothed particles dynamics was then computed along with large-eddy simulation (LES) of turbulent channel gas flow with “two-way” coupling of momentum. The calculated results are compared with the experiment of Kulick et. al. (1994) and with computation of Yamomoto et. al. (2001), where the inter-particle interaction has been simulated by hard-sphere collisions with prescribed efficiency. It has been shown that our computation with smoothed motion of particle is relatively in agreement with experiment and computations of Yamomoto et. al. (2001). At the same time, the model presented in the paper has a following advantage: it, practically, does not require an additional CPU time to account for inter-particle interactions. The turbulence attenuation by particles and the preferential concentration of particles in the low-turbulence region have been shown.

Experimental Comparison of Heat Transfer Data With Flow Visualization on a Flat Surface in an Air Fluidized Bed

1983 ◽  
Vol 105 (4) ◽  
pp. 809-816 ◽  
Author(s):  
B. Rubinsky ◽  
G. L. Starnes
Keyword(s):  
Heat Transfer ◽  
Flow Visualization ◽  
Fluidized Bed ◽  
Flow Direction ◽  
Air Flow ◽  
Solid Particles ◽  
Experimental Comparison ◽  
Transfer Coefficients ◽  
Small Surface ◽  
Transfer Data

A new experimental technique is introduced which facilitates visualization of the fluid flow phenomena occurring on a small surface immersed in an air fluidized bed. The flow visualization was correlated qualitatively with heat transfer data from the surface. Heat transfer coefficients versus air velocity curves were obtained and found to be strongly dependent on the angle of inclination of the surface relative to the air flow direction. Flow visualization has facilitated the identification of three mechanisms of heat transfer to a surface as a function of the angle of inclination and the air flow velocity. These include, conduction through a stationary layer of particles, convection through a flow of solid particles, and heat transfer by sequential contact with voids and a well mixed conglomerate of solid particles.

An Eulerian Model for Free-Shear Multiphase Turbulent Diffusion

2000 ◽  
Author(s):  
Eric Loth
Keyword(s):  
Turbulent Diffusion ◽  
Particle Density ◽  
Particle Interaction ◽  
Concentration Field ◽  
Stokes Number ◽  
Solid Particles ◽  
Navier Stokes ◽  
Eulerian Model ◽  
Density Ratios ◽  
Multi Phase

Abstract A closed-form Eulerian model was constructed for longtime diffusion of heavy or buoyant particles. This model is based on incorporation of experimentally observed turbulent diffusion features: Stokes number, crossing-trajectory, inertial limit, and continuity effects. The anisotropic model was formulated using a Csanady-based approximation for the particle diffusion ratio as equal to the ratio of the particle interaction time to local eddy integral time scale. The model favorably compares with experimental free-shear measurements and numerical Lagrangian turbulent diffusion results for a range of particle density ratios (including solid particles in gas and gas bubbles in liquid). The model for turbulent diffusion effects is suited for inclusion within multi-phase Reynolds-Averaged Navier-Stokes methods which treat the particle distribution as a continuous Eulerian concentration field.

Interaction Coefficient Between Ice Particles in Convective Melting of Granular Packed Bed

1999 ◽  
Author(s):  
J. Jiang ◽  
Y.-X. Tao
Keyword(s):  
Stokes Equations ◽  
Volume Fraction ◽  
Particle Interaction ◽  
Packed Bed ◽  
Melting Rate ◽  
Interaction Coefficient ◽  
Solid Particles ◽  
Melting Time ◽  
Ice Volume ◽  
Ice Particles

Abstract To numerically simulate the convective melting of packed bed it is necessary to determine the thermophysical properties or their constitutive equations. One of the most uncertain values among them is the solute interaction coefficient of solid particles, which represents the interaction force between solid particles and is equivalent to the viscosity term in Navier-Stokes equations if the dirty fluid model is applied. It was found from the previous study that the solute (solid particle) interaction coefficient, μs, characterizes the solubility such as the melting rate, the distribution of ice volume fraction, the velocity of ice particle, and the melting time. In this study, a parametric study based on the two-dimensional model for the convective melting of granular packed beds (Jiang et al. 1999) is conducted to determine the sensitivity of interaction coefficient to the model prediction. The packed bed considered here is collection of ice particles of various shapes. Warm water at a constant temperature enters horizontally the bed where melting takes place. Two cases are considered. One is to consider μs as constant, and the other is to consider it as a function of the ice volume fraction. The melting rate, fluid flow velocity and ice volume fraction distribution are discussed for different interaction coefficient values. An “optimal” interaction coefficient between ice particles is determined by comparing the simulation data with experimental data (Tao et al. 1998). It is found that the melting results are most sensitive to the value of constant interaction coefficient rather than to whether it is a constant or as a function of the ice volume fraction.

scholarly journals Modeling SAOS Yield Stress of Cement Suspensions: Microstructure-Based Computational Approach

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2769
Author(s):  
Neven Ukrainczyk ◽  
Mareike Thiedeitz ◽  
Thomas Kränkel ◽  
Eddie Koenders ◽  
Christoph Gehlen
Keyword(s):  
Yield Stress ◽  
Critical Strain ◽  
Van Der Waals ◽  
Particle Interaction ◽  
High Sensitivity ◽  
Salient Feature ◽  
Model Parameters ◽  
Mathematical Tool ◽  
Interaction Forces ◽  
Small Amplitude Oscillatory Shear

Two static yield stress models, one known as YODEL and the newly proposed BreakPro, based on inter-particle bond breaking probability, were employed to comparatively simulate the yield stress of cement suspensions, induced by oscillatory rheological tests with small amplitude oscillatory shear (SAOS). This yield stress occurs at a critical strain in the order of 0.01%, and is commonly attributed to the limit of the linear viscoelastic domain, where attractive forces bridge the cement particles and form a flocculated particle network. YODEL is based on van der Waals (vdW) interaction forces to describe the yield stress for flow onset at a critical strain of a few percent, developed for simple non-reactive particulate suspensions. However, due to the high pH and reactivity of cementitious suspensions, their particle interaction forces are much higher than vdW. Therefore, until now, the YODEL adaptations to cementitious suspensions did not explicitly consider the microstructural-based salient feature of the original model, but used it as an implicit fitting parameter to scale the average attractive force. In this paper, the force is inversely estimated using the full power of the two microstructural-based models, presenting a new mathematical tool for investigating the fragility of the rigid percolated structure of cement suspensions. The model parameters were calibrated on measured yield stresses obtained by SAOS measurements in a high-sensitivity rheometer. The estimated forces were found to be 5.57 (BreakPro) and 1.43 (YODEL) times higher than typical van der Waals forces. The YODEL percolation threshold of 21% turned out to be significantly lower than the one found by the BreakPro model (37%). This indicated that BreakPro modeling assumptions are better suited for the description of yield stress at SAOS critical strain than the YODEL model.

3D Modeling of an Anode Supported SOFC Using FEM and LBM

2013 ◽  
Author(s):  
Martin Andersson ◽  
Hedvig Paradis ◽  
Jinliang Yuan ◽  
Bengt Sundén
Keyword(s):  
Electron Transport ◽  
3D Model ◽  
High Current Density ◽  
Flow Direction ◽  
Transport Processes ◽  
Solid Particles ◽  
Lattice Boltzmann Model ◽  
Electrochemical Reactions ◽  
Oxygen Ions ◽  
Intermediate Temperature Range

Solid oxide fuel cells (SOFCs) are promising as energy producing device, which at this stage of its development will require extensive analysis and benefit from numerical modeling at different time- and length scales. In this study, two models based on finite element method (FEM) and Lattice Boltzmann model (LBM), respectively, are evaluated and compared for an anode-supported SOFC. First, a 3D model is developed based on the FEM, using COMSOL, of a single SOFC operating at an intermediate temperature range. Heat, gas-phase species, momentum, ion and electron transport are implemented and coupled to the kinetics of the electrochemical reactions. Secondly, a 3D model of the porous anode of a SOFC is developed using LBM to investigate the effects of electrochemical reactions on the transport processes at microscale for 3 components (H2, H2O and O2−). Parallel computing in Python is employed through the program Palabos to capture the active microscopic catalytic reaction effects on the heat and mass transport. It is found that LBM can be effectively used at a mesoscale ranging down to a microscale and proven to effectively take care of the interaction between the fluid particles and the walls of the porous media. The 3D LBM model takes into account the transport of oxygen ions within the solid particles of the SOFC anode. Both the oxygen ions and the hydrogen are mainly consumed by the reaction layer. One of the improvements in this study compared to our previous (FEM) models is the captured 3D effects which was not possible in 2D. High current density spots are identified, where the electron transport distance is short and the oxygen concentration is high. The relatively thin cathode results in a significant oxygen mole fraction gradient in the direction normal to the main flow direction.

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