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ksiazka tytuł: EXPERIMENTAL AND COMPUTATIONAL ANALYSIS OF GRANULAR MATERIAL FLOW IN MODEL SILOS autor: IRENA SIELAMOWICZ, ROBERTAS BALEVICIUS
DOSTAWA WYŁĄCZNIE NA TERYTORIUM POLSKI

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EXPERIMENTAL AND COMPUTATIONAL ANALYSIS OF GRANULAR MATERIAL FLOW IN MODEL SILOS

Wersja papierowa
Wydawnictwo: IPPT PAN
ISBN: 978-83-89687-81-4
Liczba stron: 317
Oprawa: Miękka
Wydanie: 2013 r.
Język: polski

Dostępność: dostępny
35,90 zł 32,30 zł

The study described here was undertaken to explore the phenomena occurring in silo problems. For these problems, no experimental results exist, but simpler tests for validation can be used. This book identifies theses phenomena which are presented in two chapters. The first presents experimental investigations of granular material flows with a detailed description of phenomena occurring during filling and discharge processes in silo models. It also pertains to empirical descriptions of velocities and flow rates considered via statistical analysis. The experiments were conducted using a Digital Particle Image Velocimetry Optical Flow (DPIV OF). Applying this innovative technique allowed the obtaining and identification of a large volume of quantitative data characterizing the granular material flow, such as, velocities patterns within granular material, outflow rate, deformations, strains, dilation and stagnant zones boundaries; especially in the eccentric modes of flows for the plane silo models. The chapter also includes the analysis on verification of a Radial Flow assumption. The new mathematical description of kinematic parameter b for radial flow was applied with new formula for defining velocities in radial flows. Furthermore, the DPIV technique was applied to verify mass and volume conservation in the flowing material. The results obtained in this chapter serve as the basis of further verification via numerical simulations made by the Discrete Element Method (DEM). Hence, the second Chapter discusses implementation of DEM in simulation of the processes observed during the performed experiments. The presented DEM mathematical model was applied to verify the wall stress distributions, this is presented first with a limited number of particles and then with an increased number of particles. This approach made it possible to verify parameters or indicators derived from the well-known continuum-based methods. The computational analyses presented also provides a micromedianical insight into the filling and discharge of the granular materials in the 3D silo models. In particular, this chapter deals with the results of investigation of such specific phenomena known as "a free-fall arch", material dilation forming, porosity fields evolution, distribution of stress within the granular material, outflow rates and velocity profiles. The key finding of the analysis was the comparison of the measured wall pressure distribution in the experiments with those obtained numerically with DEM, Janssen solution and the Standard Eurocod 1. It was particularly demonstrated that the wall pressure calculated by the recommended formula in the design Standard gives lower values than those obtained from the experimental measurements. While a well known Janssen‘s theory cannot be expected to represent pressures during silo discharge. Also, the analysis of the influence of rolling friction on wall pressure and velocities distributions within the flowing granular material were considered in detail. Such important phenomena like a "pressure switch" were also successfully captured numerically and experimentally during the discharge process. Finally, the general conclusions arising from the study appear to be very useful for the designers of silo structures one of the most difficult tasks in the field of civil engineering.

SPIS TREŚCI

Preface

Introduction

1. Investigations of flow processes - Experiments in silos
1.1. Experimental analysis of flow in the plane model by the DPIV
(Digital Particle Image Velocimetry) techniąue
1.1.1. Introduction
1.1.2. Basic assumptions in granular material flow
1.1.3. Theory and experiments in plane flow
1.1.4. Experimental setup
1.1.5. Results of the experiments
1.1.5.1. Stagnant zone boundaries
1.1.5.2. Velocity distributions of the flowing grains
1.1.5.3. Streamlines
1.1.5.4. Velocity profiles
1.1.5.5. Evolution of velocities and plug flow zone
1.1.5.6. Wall stresses
1.1.5.6.1. Filling and storing pressures
1.1.5.6.2. Discharge pressures
1.1.6. Theoretical analysis of vertical velocity
1.1.6.1. Analysis of the experimental results
1.1.6.2. Statistical analysis of experimental results
1.1.6.3. Empirical description of vertical velocity Vy
by the parabolic function
1.1.6.3.1. Relation between velocities in the model
1.1.6.3.2. Theoretical investigations of flow rate
1.1.6.4. Empirical description of the width of the funnel flow 2a
1.1.6.5. Theoretical description of the plug flow zone
1.1.6.6. Kinematic model
1.1.6.7. Empirical description of velocities by the Gaussian function
1.1.6.7.1. Analysis of velocities
1.1.6.7.2. Modification of kinematic model
1.1.6.7.3. Evaluation of kinematic parameter b
1.1.6.8. Theoretical description of the flow rate
1.1.6.9. Verification of accuracy of the applied models
1.1.7. Conclusions
1.2. Experimental analysis of granular flow in the converging model using
the DPIV technique
1.2.1. Introduction
1.2.2. Literature review
1.2.3. Experimental procedure
1.2.4. Mechanics of the flow
1.2.4.1. Velocity fields
1.2.4.2. Streamlines in the flowing material
1.2.4.3. Velocity profiles
1.2.4.4. Discharge flow rate
1.2.5. Empirical description of vertical velocity of moving particles
1.2.5.1. Experimental readings taken from velocity profiles
1.2.5.2. Statistical analysis of the experimental results
1.2.5.3. Statistical verification of dependence of velocity on height H
1.2.5.4. Empirical description of velocities by the parabolic function
1.2.5.5. Theoretical investigation of the flow rate
1.2.5.6. Empirical description of velocities by the Gaussian function
1.2.5.6.1. Analysis of velocities given in [128] and [141]
1.2.5.6.2. Evaluation of kinematic parameter b
1.2.5.6.3. Comparison of flow ratę value Q by the parabolic
and Gaussian solution
1.2.5.7. Radial Flow Departure
1.2.5.7.1. Verification of the Radial Flow Assumption
1.2.5.7.2. Verification of accuracy of the applied methods
1.2.6. Conclusions
1.3. Experimental analysis of eccentric flow in the plane model by the DPIV technique
1.3.1. Introduction
1.3.2. Literature review
1.3.3. Experimental procedure
1.3.4. Experimental results
1.3.4.1. Velocities of the flowing amaranth seeds. The model with
rough walls
1.3.4.2. Velocities of the flowing amaranth seeds. The model with
smooth walls
1.3.4.3. The flow of the flax-seeds in the model with
medium-rough walls
1.3.4.4. The flow of the flax-seeds in the model with
rough walls
1.3.4.5. Empirical analysis of the flow of the flax seeds in the model
with smooth walls. Discharge from the right
1.3.4.5.1. Description of velocities by the exponential function
(modified, the Gaussian type)
1.3.4.5.2. Description of velocities by the multiple regression
1.3.4.5.3. Description of velocities by ch function
1.3.4.5.4. Verification of accuracy of the applied descriptions
1.3.4.5.5. Flow rate
1.3.4.6. Empirical description of the flax seed flow in the model with
smooth wails. Discharge from the left
1.3.4.6.1. Description of velocities by the exponential function
(modified, the Gaussian type)
1.3.4.6.2. Description of velocities by ch function
1.3.4.6.3. Verification of accuracy of the applied descriptions
1.3.4.6.4. Flow rate
1.3.4.6.5. Empirical description of velocities using
"the joined functions"
1.3.4.6.6. Verification of accuracy of the solution by
"the joined functions"
1.3.4.6.7. Flow rate calculated by "the joined functions"
1.3.4.6.8. Conclusions
1.3.4.7. Eccentric filling. Discharge in the centre of the bortom
1.3.4.8. Stagnant zone boundary measurements in the model with
smooth walls. Deformations inthe material
1.3.5. Final conclusions

2. Simulations of granular material flow by the Discrete Element Method
2.1. Discrete element method: a tool for investigation of the granular material flow processes in silos
2.1.1. Introduction
2.1.2. Theoretical approaches to granular materiał simulations
2.1.3. Reviewof Discrete Element Method in modelling the silo systems
2.1.4. A discrete concept
2.1.5. A modelling technique
2.2. Qualitative predictions of granular material flow in silos, hoppers
of different shapes
2.2.1. Introduction
2.2.2. Microscopic and macroscopic analysis of granular material
behaviour in 3D flat bottomed hopper
2.2.2.1. Computational model
2.2.2.2. A microscopic analysis
2.2.2.3. A macroscopic analysis
2.2.2.4. Concluding remarks
2.2.3. Microscopic and macroscopic analysis of granular material
behaviour in 3D wedge-shaped hopper
2.2.3.1. Mathematical model
2.2.3.2. Mathematical modelling of the filling process
2.2.3.3. Mathematical modelling of the discharge process
2.2.3.4. Concluding remarks
2.2.4. A comparative analysis on granular material flow through
a space-wedged, plane-wedged and flat-bottomed hopper
2.2.4.1. Mathematical model. Basic assumptions
2.2.4.2. Computational results
2.2.4.3. Concluding remarks
2.3. Quantitative predictions of granular materiał flow in a bin: a comparison
of the computational results to the experimental data
2.3.1. Introduction
2.3.2. Experimental investigation
2.3.2.1. Setup and measurements
2.3.2.2. Material properties
2.3.3. Computational investigations
2.3.3.1. The input data and assumptions
2.3.3.2. Presentation of computational analysis
2.3.3.3. Results of the stress analysis
2.3.3.4. Results of the wali pressure analysis
2.3.3.5. Particle velocity distributions within the bin
2.3.3.6. Results of the outflow analysis
2.3.3.7. Concluding remarks
2.3.4. Discussion on the scale effects

Bibliography

Appendix 1

Appendix 2

Appendix 3

Appendix 4

 

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