scholarly journals Numerical Investigation of Jamming of Solid Particles in a Straight Pipe

1996 ◽  
Author(s):  
Yi Sun ◽  
Oleg Vinogradov
Keyword(s):  
Fluid Flow ◽  
Fluid Velocity ◽  
Solid Particles ◽  
Spherical Particles ◽  
Critical Parameters ◽  
Straight Pipe ◽  
Volumetric Density ◽  
Physical Experiments ◽  
Variable Topology ◽  
Two Parameters

The flow of fluids containing solid particles is numerically simulated in order to determine the critical parameters of the system leading to a jam. Two parameters are varied: the volumetric density of solid particles and the velocity of fluid flow. The energy dissipation in the system is due to dry friction losses and collisions. The results presented are based on the mathematical models of granular materials treated as multibody systems with variable topology. The fluid flow is considered to be potential. It is shown that jamming strongly depends on the volumetric density of particles and fluid velocity. The results of numerical experiments are in qualitative agreement with physical experiments of flow of spherical particles in a pipe.

Computer Simulations of Low Concentrations Slurry Flows in Pipelines

2000 ◽  
Author(s):  
Yuri Leonenko ◽  
Oleg Vinogradov
Keyword(s):  
Fluid Velocity ◽  
Dynamics Model ◽  
Simple Experiment ◽  
Heterogeneous Flow ◽  
Volumetric Density ◽  
Low Concentrations ◽  
System Of Particles ◽  
Slurry Flows ◽  
Critical Velocities ◽  
Two Parameters

In the paper a discrete system of particles carried by fluid is considered in a planar motion. The volumetric density of particles is taken between 1% and 2% so that they can be treated within the framework of a discrete dynamics model. The fluid is then considered as a carrier of particles. The Landau-Lifshitz concept of turbulence is used to describe the fluctuating part of fluid velocity. This approach is applied to simulate different regimes (laminar and turbulent) and various states of particle motion (moving bed, heterogeneous flow, and homogeneous flow) using only two parameters, which have to be determined experimentally. These two parameters, found for a particular pipe and for a particular velocity from a simple experiment, then have been used for simulations of flow for other pipe diameters and different velocities. The results agree favorably with experimental observations of the type of slurry flow and critical velocities identifying transitions from one type to another.

scholarly journals Influence of the particle shape on the impact force of lahar on an obstacle

2021 ◽  
Vol 249 ◽  
pp. 03010
Author(s):  
Rime Chehade ◽  
Bastien Chevalier ◽  
Fabian Dedecker ◽  
Pierre Breul
Keyword(s):  
Particle Shape ◽  
Urban Areas ◽  
Large Scale ◽  
Distinct Element ◽  
Fluid Velocity ◽  
Solid Particles ◽  
Impact Pressure ◽  
Spherical Particles ◽  
Coupling Scheme ◽  
The Impact

Lahars represent natural phenomena that can generate severe damage in densely populated urban areas. The evaluation of pressures generated by these mass flows on constructions (buildings, infrastructure…) is crucial for civil protection and assessment of physical vulnerability. The existing tools to model the spread of flows at large scale in densely populated urban areas remain inaccurate in the estimation of mechanical efforts. A discrete numerical model is developed for evaluating debris flow (DF) impact pressures at the local scale of one structure. The large-sized solid particles are modelled explicitly using Distinct Element Method (DEM) and the fine-grained solid particles are integrated in a fluid phase which generates two effects on the movement of particles, i.e. buoyancy and drag. Fluid velocity field and the fluid free surface are obtained from Computational Fluid Dynamics (CFD) code then imported in the DEM simulation in a one way coupling scheme. In this paper, the influence of particle shape on the impact forces generated on the obstacle is investigated: spherical particles and polygonal rigid blocks (r-blocks) are considered. The shape of the particle influences the contact surface and therefore the impact pressure. With an angular shape and several facets like r-blocks, the impact pressure on an obstacle is more important for a flow with the same characteristics.

Simulation of Multiphase Turbulent Fluid Flow Through an Electrolytic Cell

2003 ◽  
Author(s):  
Roald Akberov ◽  
Valery Ponyavin ◽  
Yitung Chen ◽  
Hsuan-Tsung Hsieh ◽  
Darrell W. Pepper
Keyword(s):  
Fluid Flow ◽  
Electrolytic Cell ◽  
Hydrogen Gas ◽  
Solid Particles ◽  
Force Balance ◽  
Spherical Particles ◽  
Turbulent Fluid Flow ◽  
Turbulent Fluid ◽  
Flow Through ◽  
Volume Method

A Finite Volume Method was applied to a two-dimensional model for multiphase turbulent fluid flow inside an electrolytic cell. The model is based on solving the momentum equations for the single continuous liquid phase. In the model, solid particles and hydrogen gas bubbles are treated as inert spherical particles. Once the momentum equations are solved, trajectories of the particles can be calculated by integrating the force balance on the particle, which can be expressed in a Lagrangian reference frame. Turbulence is modeled via utilizing the standard k-ε model. The paper also discusses the computational meshes, which can be used for the simulation. It is shown that usage of the boundary layer type elements decreases the total number of computational nodes while maintaining the same accuracy in calculation. It is also shown that minute changes in the geometry of the cell, such as an increase in the thickness of the plate, results in obtaining more favorable flow patterns for taking solid particles away from the electrolytic cell.

Oscillatory Compressional Behavior of Articular Cartilage and Its Associated Electromechanical Properties

1981 ◽  
Vol 103 (4) ◽  
pp. 280-292 ◽  
Author(s):  
R. C. Lee ◽  
E. H. Frank ◽  
A. J. Grodzinsky ◽  
D. K. Roylance
Keyword(s):  
Fluid Flow ◽  
Articular Cartilage ◽  
Molecular Mechanisms ◽  
Fluid Velocity ◽  
Streaming Potential ◽  
Usual Sense ◽  
Frequency Range ◽  
Confined Compression ◽  
Streaming Potentials ◽  
Compressive Stiffness

The compressive stiffness of articular cartilage was examined in oscillatory confined compression over a wide frequency range including high frequencies relevant to impact loading. Nonlinear behavior was found when the imposed sinusoidal compression amplitude exceeded a threshold value that depended on frequency. Linear behavior was attained only by suitable control of the compression amplitude. This was enabled by real time Fourier analysis of data which provided an accurate assessment of the extent of nonlinearity. For linear viscoelastic behavior, a stiffness could be defined in the usual sense. The dependence of the stiffness on ionic strength and proteoglycan content showed that electrostatic forces between matrix charge groups contribute significantly to cartilage’s compressive stiffness over the 0.001 to 20 Hz frequency range. Sinusoidal streaming potentials were also generated by oscillatory compression. A theory relating the streaming potential field to the fluid velocity field is derived and used to interpret the data. The observed magnitude of the streaming potential suggests that interstitial fluid flow is significant to cartilage behavior over the entire frequency range. The use of simultaneous streaming potential and stiffness data with an appropriate theory appears to be an important tool for assessing the relative contribution of fluid flow, intrinsic matrix viscoelasticity, or other molecular mechanisms to energy dissipation in cartilage. This method is applicable in general to hydrated, charged polymers.

scholarly journals CFD SIMULATION OF EROSION BY PARTICLE COLLISION IN U-BEND AND HELICAL TYPE PIPES

2020 ◽  
Vol 14 (2) ◽  
pp. 1-13
Author(s):  
Mohammad Sheikh Mamoo ◽  
Ataallah Soltani Goharrizi ◽  
Bahador Abolpour
Keyword(s):  
Mass Flow ◽  
Mean Curvature ◽  
Particle Density ◽  
Fluid Velocity ◽  
Diameter Ratio ◽  
Solid Particles ◽  
Pipe Diameter ◽  
Design Parameters ◽  
Curvature Radius ◽  
Rate Of Penetration

Erosion caused by solid particles in curve pipes is one of the major concerns in the oil and gas industries. Small solid particles flow with a carrier liquid fluid and impact the inner wall of the piping, valves, and other equipment. These components face a high risk of solid particle erosion due to the constant collision, which may result in equipment malfunctioning and even failure. In this study, the two-way coupled Eulerian-Lagrangian method with the Oka erosion and Grant and Tabakoff particle-wall rebound models approach is employed to simulate the liquid-solid flow in U-bend and helical pipes using computational fluid dynamics. The effects of operating parameters (inlet fluid velocity and temperature, particle density and diameter, and mass flow rate) and design parameters (mean curvature radius/pipe diameter ratio) are investigated on the erosion of these tubes walls. It is obtained that increasing the fluid velocity and temperature, particle mass flow and particle density increase the penetration rate, particle diameter affects the rate of penetration, and increasing mean curvature radius/pipe diameter ratio decreases the rate of penetration.

Raman-Microsampling Technique Applying Optical Levitation by Radiation Pressure

1984 ◽  
Vol 38 (1) ◽  
pp. 78-83 ◽  
Author(s):  
R. Thurn ◽  
W. Kiefer
Keyword(s):  
Radiation Pressure ◽  
Optical Potential ◽  
Solid Particles ◽  
Spherical Particles ◽  
Exciting Light ◽  
Potential Wells ◽  
Ion Laser ◽  
Optical Levitation ◽  
Argon Ion ◽  
Microprobe Technique

We report on a new Raman microprobe technique where micron-sized solid particles are trapped in stable optical potential wells using only the force of radiation pressure from a continuous gas laser. We demonstrate this technique with Raman spectra from spherical and non-spherical particles of sizes ranging between 10–30 μm. The particles are stably supported by a vertical directed focused TEM00-mode cw argon ion laser of ∼500 mW. The latter simultaneously serves as the exciting light source. Several suggestions for improvements of this technique are made.

Wave Action on Double-Cylinder Structure With Perforated Outer Wall

2003 ◽  
Author(s):  
Yucheng Li ◽  
Lu Sun ◽  
Bin Teng
Keyword(s):  
Numerical Experiments ◽  
Fluid Velocity ◽  
Wave Interaction ◽  
Outer Wall ◽  
Wave Force ◽  
Wave Loads ◽  
Linear Solution ◽  
Perforated Wall ◽  
Physical Experiments ◽  
Run Up

Based on an eigenfunction expansion of velocity potential and a linear model between the pressure difference between two sides of a perforated wall and the fluid velocity inside it, a semi-analytic linear solution has been acquired for wave interaction with a combined cylinder with an solid interior column surrounded by a coaxial exterior column with perforated wall at a section in azimuthal direction. Numerical experiments have been carried out to examine the influences on the wave force and wave run-up on the combined cylinders with perforated wall by the porous coefficient, the size of the perforated section, and the ratio between the radii of the interior and the exterior columns. This paper also presents the comparison between the numerical experiments results and the physical experiments results. It is acceptable of the comparison of these two results. The combined cylinder may reduce both the wave run-up and the wave loads on it through combination of certain parameters.

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