Table of Contents

1 Introduction 1

1.1 Adhesive Particle Flow 1

1.2 Example Systems 2

1.3 Collision and Agglomeration of Particles in Turbulence 4

1.4 Migration of Microparticles in an Electrostatic Field 6

1.5 Deposition of Microparticles and Clogging Phenomenon 9

1.6 Discrete Element Methods for Adhesive Particles 12

1.7 A Road Map to Chaps. 2–6 13

References 14

2 A Fast Discrete Element Method for Adhesive Particles 17

2.1 Introduction 17

2.2 Discrete Element Method for Adhesive Particles 18

2.3 Critical Sticking Velocity for Two Colliding Particles 20

2.3.1 Temporal Evolution of the Collision Process 22

2.3.2 Prediction of the Critical Sticking Velocity 25

2.3.3 Effect of Particle Size 29

2.4 A Fast Adhesive DEM 31

2.4.1 Accelerating Adhesive DEM Using Reduced Stiffness 31

2.4.2 Modi?ed Models for Rolling and Sliding Resistances 34

2.5 Determination of Parameters in Adhesive DEM 36

2.5.1 An Inversion Procedure to Set Parameters in Adhesive DEM 36

2.5.2 Comparison Between Experimental and DEM Results 39

2.6 Test on Packing Problem 40

2.6.1 Packing Fraction and Coordination Number 43

2.6.2 Local Structure of Packings 45

2.6.3 Interparticle Overlaps and Normal Forces 46

2.7 Summary 48

References 49

3 Agglomeration of Microparticles in Homogenous Isotropic Turbulence 51

3.1 Introduction 51

3.2 Methods 52

3.2.1 Fluid Phase Calculation 52

3.2.2 Equation of Motion for Solid Particles 53

3.2.3 Multiple-time Step Framework 54

3.2.4 Simulation Conditions 55

3.2.5 Identi?cation of Collision, Rebound and Breakage Events 57

3.2.6 Smoluchowski’s Theory 59

3.3 Collision Rate, Agglomerate Size and Structure 60

3.4 Effect of Stokes Number 62

3.5 Exponential Scaling of Early-Stage Agglomerate Size 62

3.6 Agglomeration Kernel and Population Balance Modelling 64

3.7 Effect of Adhesion on Agglomeration 65

3.8 Effect of Adhesion on Breakage of Agglomerates 68

3.9 Formulation of the Breakage Rate 68

3.10 Agglomerate Size Dependence of the Breakage Rate 76

3.11 Role of Flow Structure 76

3.12 Conclusions 78

References 79

4 Migration of Cloud of Low-Reynolds-Number Particles with Coulombic and Hydrodynamic Interactions 81

4.1 Introduction 81

4.2 Formulation of Problem 81

4.3 Effect of Coulomb Repulsion on Cloud Shape 84

4.3.1 Cloud Shape 84

4.3.2 Effect of Fluid Inertia 87

4.3.3 Stability of the Cloud 88

4.4 Evolution of Particle Cloud Under Strong Repulsion 91

4.4.1 Scaling Analysis and Continuum Description 91

4.4.2 Prediction of Cloud Size and Migrating Velocity 93

4.4.3 Discussion 97

4.5 Summary 98

References 99

5 Deposition of Microparticles with Coulomb Repulsion 101

5.1 Introduction 101

5.2 Models and Methods 102

5.2.1 Simulation Conditions 102

5.2.2 Forces on Particles 103

5.2.3 Average-Field Calculation for Coulomb Interactions

in 2D Periodic System 103

5.3 Effects of Coulomb Interaction on Packing Structure 106

5.4 Scaling Analysis of the Interparticle Force 109

5.5 Governing Parameters for the Packing Structure 112

5.6 Phase Diagram 115

5.7 Summary 117

References 118

6 Deposition of Charged Micro-Particles on Fibers: Clogging Problem 119

6.1 Introduction 119

6.2 Models and Method 120

6.2.1 Simulation Conditions: Two Fiber System 120

6.2.2 Gas Phase Simulation 121

6.2.3 Solid-Phase: Discrete-Element Method (DEM) 122

6.2.4 Governing Parameters 123

6.3 Clogging/Non-clogging Transition 124

6.4 Measurement of Particle Capture Ef?ciency 127

6.4.1 Repulsion Effect: The Critical State 128

6.4.2 Structure Effect 130

6.5 Summary 133

References 134

7 Conclusions and Perspective 135

7.1 Conclusions 135

7.2 Future Work 137

References 138