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Particle Methods for Modelling Granular Material Flow
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials. (Solid Mechanics)ORCID iD: 0000-0001-5206-6894
2019 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Partikelmetoder för modelleringav granulära flöden (Swedish)
Abstract [en]

Granular materials are very abundant in nature and are often used in industry, wherethe dynamics of granular material ow is of relevance in many processes. There arestrong economic and environmental incentives for increased eciency in handling andtransporting granular materials. Despite being common, the mechanical behaviour ofgranular materials remains challenging to predict and a unifying theory describing granularmaterial ow does not exist. If the ambition is an ecient industrial handling ofgranular materials, increased knowledge and understanding of their behaviour is of utmostimportance. In the present thesis, particle-based numerical methods are used formodelling granular material ow. In this context, particle-based methods refer to the useof particles as a discretization unit in numerical methods. Particle-based modelling canbe divided in two main approaches: discrete and continuum. In a discrete approach, eachphysical particle in the granular mass is modelled as a discrete particle. Newton's secondlaw of motion combined with a contact model governs the behaviour of the granular mass.In a continuum approach, the granular material is modelled using a constitutive law relatingstresses and strains. As a discrete approach, the discrete element method (DEM) isused and as a continuum approach the smoothed particle hydrodynamics (SPH) methodand the particle nite element method (PFEM) are used. Furthermore, an experimentalmethodology able to capture the ow behaviour of granular materials is developed. Themethodology is based on digital image correlation and it is used to obtain the in-planevelocity eld for granular material ow. This thesis covers experimental measurementsand numerical modelling of granular material ow in a number of applications. In paperA, an experimental powder lling rig is used to study the ow of sand. With thisrig, a methodology for obtaining the in-plane velocity eld of a granular material ow isdeveloped. This methodology is applied in paper B, to quantify the ow of a tungstencarbide powder. The powder is modelled using the SPH method, with good agreementto experimental results. In paper C, the ow of potassium chloride fertilizers is modelledusing the SPH method, and in Paper D the PFEM is explored for modelling of granularmaterial ow. The numerical models are validated against experimental results, suchas in-plane velocity eld measurements. In paper E, coupled nite element, DEM andPFEM models are used to model the physical interactions of grinding media, slurry andmill structure and in a stirred media mill. The ndings in the present thesis support theestablishment of particle-based numerical methods for modelling granular material owin a number of dierent applications. Furthermore, a methodology for calibration andvalidation of numerical models is developed.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019.
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-73199ISBN: 978-91-7790-332-1 (print)ISBN: 978-91-7790-333-8 (electronic)OAI: oai:DiVA.org:ltu-73199DiVA, id: diva2:1296317
Public defence
2019-05-16, E231, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2019-03-15 Created: 2019-03-14 Last updated: 2019-04-26Bibliographically approved
List of papers
1. Experimental methodology for study of granular material flow using digital speckle photography
Open this publication in new window or tab >>Experimental methodology for study of granular material flow using digital speckle photography
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2016 (English)In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 155, p. 524-536Article in journal (Refereed) Published
Abstract [en]

Granular material flow occurs in many industrial applications, and the characteristics of such flow is challenging to measure. Therefore, an experimental method that captures the flow behavior at different loading situations is desired.

In this work, experimental measurements of granular material flow with digital speckle photography (DSP) are carried out. The granular flow process is recorded with a high-speed camera; the image series are then analyzed using the DSP method. This approach enables field data such as displacement, velocity, and strain fields to be visualized during the granular material flow process. Three different scenarios were studied: free surface flow in a fill shoe, flow without a free surface in a fill shoe, and the rearrangement of material in a cavity. The results showed that it is possible to obtain field data of the motion of particles for all three scenarios with the DSP technique. The presented experimental methodology can be used to capture complex flow behavior of granular material.

National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-59694 (URN)10.1016/j.ces.2016.09.010 (DOI)000385600400045 ()2-s2.0-84987642035 (Scopus ID)
Note

Validerad; 2016; Nivå 2; 2016-10-12 (andbra)

Available from: 2016-10-12 Created: 2016-10-12 Last updated: 2019-03-14Bibliographically approved
2. Study of Powder Filling Using Experimental and Numerical Methods
Open this publication in new window or tab >>Study of Powder Filling Using Experimental and Numerical Methods
2016 (English)Conference paper, Published paper (Refereed)
Abstract [en]

This work covers both experimental measurements and numerical modelling of powder filling. Experimental measurements with digital speckle photography (DSP) are used to study powder flow during die filling. DSP measurements are realized by recording the powder filling process with a high speed video camera. The image series are then evaluated using an image correlation technique. By this, velocity and strain field data during the filling process can be visualised. DSP measurements are also supporting the development of a numerical model of the process. In this work the smoothed particle hydrodynamics (SPH) method is used to model the powder filling process. The numerical results are similar compared to the DSP measurements when comparing velocity fields during powder filling. The SPH model is further used to evaluate the density distribution after filling. Experimental measurements combined with simulation are powerful tools to increase the knowledge of the powder filling process.

National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-60482 (URN)
Conference
World PM2016 Congress & Exhibition, Hamburg, October 9-13 2016
Available from: 2016-11-16 Created: 2016-11-16 Last updated: 2019-03-14Bibliographically approved
3. Experimental and numerical study of potassium chloride flow using smoothed particle hydrodynamics
Open this publication in new window or tab >>Experimental and numerical study of potassium chloride flow using smoothed particle hydrodynamics
2018 (English)In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 116, p. 88-100Article in journal (Refereed) Published
Abstract [en]

Materials in granular form are widely used in industry and in the society as a whole. Granular materials can have various behaviours and properties. An accurate prediction of their flow behaviour is important to avoid handling and transportation issues. In this study, the flow behaviour of dry potassium chloride (KCl) in granular form was investigated experimentally and simulated numerically. The aim was to develop numerical tools to predict the flow of KCl in transportation and handling systems and granular material flow in various industrial applications. Two experimental setups were used to quantify the flow of KCl. In the first setup, the collapse of an axisymmetric granular column was investigated. In the second setup, digital image correlation was used to obtain velocity field measurements of KCl during the discharge of a flat-bottomed silo. The two experiments were represented numerically using two-dimensional computational domains. The smoothed particle hydrodynamics method was used for the simulations, and a pressure-dependent, elastic-plastic constitutive model was used to describe the granular materials. The numerical results were compared to the experimental observations, and an adequate qualitative and quantitative agreement was found for the granular column collapse and the silo discharge. Overall, the simulated flow patterns showed adequate agreement with the experimental results obtained in this study and with the observations reported in the literature. The experimental measurements, in combination with the numerical simulations, presented in this study adds to the knowledge of granular material flow prediction. The results of this study highlights the potential of numerical simulation as a powerful tool to increase the knowledge of granular material handling operations.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-62669 (URN)10.1016/j.mineng.2017.11.003 (DOI)000424172900012 ()
Note

Validerad;2018;Nivå 2;2018-01-25 (andbra)

Available from: 2017-03-24 Created: 2017-03-24 Last updated: 2019-03-14Bibliographically approved
4. The particle finite element method for transient granular material flow: modelling and validation
Open this publication in new window or tab >>The particle finite element method for transient granular material flow: modelling and validation
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2020 (English)In: Computational Particle Mechanics, ISSN 2196-4378Article in journal (Refereed) Epub ahead of print
Abstract [en]

The prediction of transient granular material flow is of fundamental industrial importance. The potential of using numerical methods in system design for increasing the operating efficiency of industrial processes involving granular material flow is huge. In the present study, a numerical tool for modelling dense transient granular material flow is presented and validated against experiments. The granular materials are modelled as continuous materials using two different constitutive models. The choice of constitutive models is made with the aim to predict the mechanical behaviour of a granular material during the transition from stationary to flowing and back to stationary state. The particle finite element method (PFEM) is employed as a numerical tool to simulate the transient granular material flow. Use of the PFEM enables a robust treatment of large deformations and free surfaces. The fundamental problem of collapsing rectangular columns of granular material is studied experimentally employing a novel approach for in-plane velocity measurements by digital image correlation. The proposed numerical model is used to simulate the experimentally studied column collapses. The model prediction of the in-plane velocity field during the collapse agrees well with experiments.

Place, publisher, year, edition, pages
Springer, 2020
Keywords
Particle finite element method, Transient granular material flow, Constitutive modelling, Strain-rate-dependent strength, Digital image correlation
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-73197 (URN)10.1007/s40571-020-00317-6 (DOI)000515975800001 ()
Available from: 2019-03-14 Created: 2019-03-14 Last updated: 2020-03-13
5. A novel approach for modelling of physical interactions between slurry, grinding media and mill structure in wet stirred media mills
Open this publication in new window or tab >>A novel approach for modelling of physical interactions between slurry, grinding media and mill structure in wet stirred media mills
2020 (English)In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 148, article id 106180Article in journal (Refereed) Published
Abstract [en]

Wet comminution is an important process in the mineral processing industry. Modelling of wet comminution in stirred media mills requires the simultaneous modelling of grinding media, a moving internal stirrer, and slurry. In the present study, a novel approach for modelling the physical interactions between slurry, grinding media and mill structure in a stirred media mill is presented. The slurry is modelled with the particle finite element method (PFEM). The grinding media is modelled using the discrete element method (DEM) and the mill structure is modelled using the finite element method (FEM). The interactions between slurry, grinding media and mill structure are modelled by two-way couplings between the PFEM, the DEM and the FEM models. The coupled model of the present study is used to predict the motion of slurry and grinding media, and to calculate the power draw during wet comminution in a pilot scale horizontal stirred media mill. Furthermore, the model is used to compare a Newtonian and a non-Newtonian model of the slurry, where the non-Newtonian model is used to capture experimentally observed shear-thinning. The coupled PFEM-DEM-FEM model preserves the robustness and efficiency of each of the methods and it gives the possibility to use large time increments for the fluid, greatly reducing the computational expense. The coupled model of the present work provide information on the complex dynamics of slurry and grinding media. The numerical model is shown to be a useful tool for increasing the knowledge and understanding of wet comminution in stirred media mills.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Particle finite element method, Discrete element method, Coupled models, Stirred media mills
National Category
Applied Mechanics Metallurgy and Metallic Materials
Research subject
Mineral Processing; Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-73198 (URN)10.1016/j.mineng.2019.106180 (DOI)
Note

Validerad;2020;Nivå 2;2020-02-04 (johcin)

Available from: 2019-03-14 Created: 2019-03-14 Last updated: 2020-02-04Bibliographically approved

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