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\n  \n 2023\n \n \n (1)\n \n \n
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\n \n\n \n \n \n \n \n \n Particle size segregation and diffusion in saturated granular flows: Implications for grain sorting in debris flows.\n \n \n \n \n\n\n \n Cui, K. F.; Zhou, G. G.; Jing, L.; Xie, Y.; and Lu, X.\n\n\n \n\n\n\n In Pirulli, M.; Leonardi, A.; and Vagnon, F., editor(s), E3S Web of Conferences, volume 415, pages 01003, 2023. \n \n\n\n\n
\n\n\n\n \n \n \"ParticlePaper\n  \n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
\n 
@inproceedings{cui_particle_2023,\n\ttitle = {Particle size segregation and diffusion in saturated granular flows: {Implications} for grain sorting in debris flows},\n\tvolume = {415},\n\turl = {https://www.e3s-conferences.org/10.1051/e3sconf/202341501003},\n\tdoi = {10.1051/e3sconf/202341501003},\n\tabstract = {Sorting of rocks, boulders, and silt/sand-sized particles according to their size is a characteristic feature of debris flow deposits and is an active process during flow which significantly affects the mobility. The degree at which size sorting occurs in debris flows depends on the relative magnitudes of granular processes such as particle size segregation and diffusion. Since debris flows are fluid-saturated phenomena, accurate modelling of size sorting requires the understanding of the influence of fluids on these processes, which have not been systematically studied. Here, we present simulation results and the associated empirical expressions for particle size segregation and diffusion which take into account fluid effects due to buoyant and drag forces. These expressions are developed through scaling analysis of data obtained from coupled granular-fluid simulations of saturated bi-disperse mixtures under simple shear. We further show that using these scaling relationships, an existing segregation-diffusion continuum equation can be extended to model particle sorting in debris flows with various types of fluids.},\n\tjournal = {E3S Web of Conf.},\n\tbooktitle = {{E3S} {Web} of {Conferences}},\n\tauthor = {Cui, Kahlil Fredrick and Zhou, Gordon G.D. and Jing, Lu and Xie, Yunxu and Lu, Xueqiang},\n\teditor = {Pirulli, M. and Leonardi, A. and Vagnon, F.},\n\tyear = {2023},\n\tpages = {01003}\n}\n\n\n
\n
\n\n\n
\n Sorting of rocks, boulders, and silt/sand-sized particles according to their size is a characteristic feature of debris flow deposits and is an active process during flow which significantly affects the mobility. The degree at which size sorting occurs in debris flows depends on the relative magnitudes of granular processes such as particle size segregation and diffusion. Since debris flows are fluid-saturated phenomena, accurate modelling of size sorting requires the understanding of the influence of fluids on these processes, which have not been systematically studied. Here, we present simulation results and the associated empirical expressions for particle size segregation and diffusion which take into account fluid effects due to buoyant and drag forces. These expressions are developed through scaling analysis of data obtained from coupled granular-fluid simulations of saturated bi-disperse mixtures under simple shear. We further show that using these scaling relationships, an existing segregation-diffusion continuum equation can be extended to model particle sorting in debris flows with various types of fluids.\n
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\n  \n 2021\n \n \n (1)\n \n \n
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\n \n\n \n \n \n \n \n \n Exploring shear-induced segregation in controlled-velocity granular flows.\n \n \n \n \n\n\n \n Jing, L.; Ottino, J. M.; Lueptow, R. M.; and Umbanhowar, P. B.\n\n\n \n\n\n\n In Aguirre, M.; Luding, S.; Pugnaloni, L.; and Soto, R., editor(s), EPJ Web of Conferences, volume 249, pages 03012, 2021. \n \n\n\n\n
\n\n\n\n \n \n \"ExploringPaper\n  \n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
\n 
@inproceedings{jing_exploring_2021,\n\ttitle = {Exploring shear-induced segregation in controlled-velocity granular flows},\n\tvolume = {249},\n\tissn = {2100-014X},\n\turl = {https://www.epj-conferences.org/10.1051/epjconf/202124903012},\n\tdoi = {10.1051/epjconf/202124903012},\n\tabstract = {Particle segregation in geophysical and industrial granular flows is typically driven by gravity and shear. While gravity-induced segregation is relatively well understood, shear-induced segregation is not. In particular, what controls segregation in the absence of gravity and the interplay between shear- and gravity-driven segregation remain unclear. Here, we explore the shear-induced segregation force on an intruder particle in controlled-velocity granular flows where the shear profile is systematically varied. The shear-induced segregation force is found to be proportional to the shear rate gradient, which effectively pushes the large intruder from lower to higher shear rate regions. A scaling law is developed for the segregation force that is accurate over a wide range of overburden pressures and shear rates, and hence inertial numbers.},\n\tbooktitle = {{EPJ} {Web} of {Conferences}},\n\tauthor = {Jing, Lu and Ottino, Julio M. and Lueptow, Richard M. and Umbanhowar, Paul B.},\n\teditor = {Aguirre, M.A. and Luding, S. and Pugnaloni, L.A. and Soto, R.},\n\tyear = {2021},\n\tpages = {03012}\n}\n\n
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\n\n\n
\n Particle segregation in geophysical and industrial granular flows is typically driven by gravity and shear. While gravity-induced segregation is relatively well understood, shear-induced segregation is not. In particular, what controls segregation in the absence of gravity and the interplay between shear- and gravity-driven segregation remain unclear. Here, we explore the shear-induced segregation force on an intruder particle in controlled-velocity granular flows where the shear profile is systematically varied. The shear-induced segregation force is found to be proportional to the shear rate gradient, which effectively pushes the large intruder from lower to higher shear rate regions. A scaling law is developed for the segregation force that is accurate over a wide range of overburden pressures and shear rates, and hence inertial numbers.\n
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\n  \n 2018\n \n \n (2)\n \n \n
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\n \n\n \n \n \n \n \n Coupled fluid-particle modeling of submerged granular collapse.\n \n \n \n\n\n \n Jing, L.; Yang, G. C.; Kwok, C. Y.; and Sobral, Y. D.\n\n\n \n\n\n\n In Giovine, P.; Mariano, P. M.; and Mortara, G., editor(s), Micro to MACRO Mathematical Modelling in Soil Mechanics, of Trends in Mathematics, pages 187–194, 2018. Springer International Publishing\n \n\n\n\n
\n\n\n\n \n\n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n \n \n \n \n \n \n\n\n\n
\n 
@inproceedings{jing_coupled_2018,\n\tseries = {Trends in {Mathematics}},\n\ttitle = {Coupled fluid-particle modeling of submerged granular collapse},\n\tisbn = {978-3-319-99474-1},\n\tabstract = {We perform coupled fluid-particle modeling to understand the collapse of underwater granular columns in comparison with dry cases, with a variety of initial aspect ratios. Our results show that the submerged collapse leads to a shorter runout and thicker front due to the resistance provided by the ambient fluid. An interesting process of vortex formation is observed in the fluid as particles turn into a shear flow. At high aspect ratios, the vortex in water can significantly modify the surface morphology of the final deposit due to the fluid inertia developed on the surface of the granular layer.},\n\tbooktitle = {Micro to {MACRO} {Mathematical} {Modelling} in {Soil} {Mechanics}},\n\tpublisher = {Springer International Publishing},\n\tauthor = {Jing, L. and Yang, G. C. and Kwok, C. Y. and Sobral, Y. D.},\n\teditor = {Giovine, Pasquale and Mariano, Paolo Maria and Mortara, Giuseppe},\n\tyear = {2018},\n\tkeywords = {Granular collapse, CFD-DEM, Submerged granular flow},\n\tpages = {187--194}\n}\n\n\n
\n
\n\n\n
\n We perform coupled fluid-particle modeling to understand the collapse of underwater granular columns in comparison with dry cases, with a variety of initial aspect ratios. Our results show that the submerged collapse leads to a shorter runout and thicker front due to the resistance provided by the ambient fluid. An interesting process of vortex formation is observed in the fluid as particles turn into a shear flow. At high aspect ratios, the vortex in water can significantly modify the surface morphology of the final deposit due to the fluid inertia developed on the surface of the granular layer.\n
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\n \n\n \n \n \n \n \n \n Effect of particle size segregation in debris flow deposition: A preliminary study.\n \n \n \n \n\n\n \n Jing, L.; Kwok, F. C. Y.; Zhao, T.; and Zhou, J.\n\n\n \n\n\n\n In Farid, A.; and Chen, H., editor(s), Proceedings of GeoShanghai 2018 International Conference: Geoenvironment and Geohazard, pages 73–80, Singapore, 2018. Springer Singapore\n \n\n\n\n
\n\n\n\n \n \n \"EffectPaper\n  \n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
\n 
@inproceedings{farid_effect_2018,\n\taddress = {Singapore},\n\ttitle = {Effect of particle size segregation in debris flow deposition: {A} preliminary study},\n\tisbn = {9789811301278 9789811301285},\n\tshorttitle = {Effect of particle size segregation in debris flow deposition},\n\turl = {http://link.springer.com/10.1007/978-981-13-0128-5_9},\n\tabstract = {To understand the effect of size segregation in the depositional process of debris flows, both flume experiments at the laboratory scale and numerical simulations using the discrete element method (DEM) are performed. A variety of particle size distributions with coarse and fine particles are adopted. It is found that larger particles tend to reach the front of the final deposits, while small particles are accumulated at the tail of the flows. Quantitative agreement is achieved in the DEM simulations, where rolling resistance and geometric roughness at boundaries are adopted to account for the effect of particle shape. With the DEM results, the effect of segregation on the runout distance is studied from the perspective of energy dissipation. The progress of segregation is analyzed in detail, which revealed that segregation occur slowly while the flow is propagating rapidly over the slopes; it becomes significant during the deposition stage, where more large particles are found near the surface. The effect of segregation in debris flow deposition can help better predict the runout distance and impact pressure, which is crucial in the assessment and mitigation of debris flow-related natural hazards.},\n\tlanguage = {en},\n\turldate = {2018-05-15},\n\tbooktitle = {Proceedings of {GeoShanghai} 2018 {International} {Conference}: {Geoenvironment} and {Geohazard}},\n\tpublisher = {Springer Singapore},\n\tauthor = {Jing, Lu and Kwok, Fiona C. Y. and Zhao, Tao and Zhou, Jiawen},\n\teditor = {Farid, Arvin and Chen, Hongxin},\n\tyear = {2018},\n\tdoi = {10.1007/978-981-13-0128-5_9},\n\tpages = {73--80}\n}\n\n
\n
\n\n\n
\n To understand the effect of size segregation in the depositional process of debris flows, both flume experiments at the laboratory scale and numerical simulations using the discrete element method (DEM) are performed. A variety of particle size distributions with coarse and fine particles are adopted. It is found that larger particles tend to reach the front of the final deposits, while small particles are accumulated at the tail of the flows. Quantitative agreement is achieved in the DEM simulations, where rolling resistance and geometric roughness at boundaries are adopted to account for the effect of particle shape. With the DEM results, the effect of segregation on the runout distance is studied from the perspective of energy dissipation. The progress of segregation is analyzed in detail, which revealed that segregation occur slowly while the flow is propagating rapidly over the slopes; it becomes significant during the deposition stage, where more large particles are found near the surface. The effect of segregation in debris flow deposition can help better predict the runout distance and impact pressure, which is crucial in the assessment and mitigation of debris flow-related natural hazards.\n
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\n  \n 2017\n \n \n (2)\n \n \n
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\n \n\n \n \n \n \n \n \n Effect of geometric base roughness on size segregation.\n \n \n \n \n\n\n \n Jing, L.; Kwok, C. Y.; Leung, Y. F.; and Sobral, Y. D.\n\n\n \n\n\n\n In EPJ Web of Conferences, volume 140, pages 03056, 2017. \n \n\n\n\n
\n\n\n\n \n \n \"EffectPaper\n  \n \n\n \n \n doi\n  \n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
\n 
@inproceedings{jing_effect_2017,\n\ttitle = {Effect of geometric base roughness on size segregation},\n\tvolume = {140},\n\turl = {https://doi.org/10.1051/epjconf/201714003056},\n\tdoi = {10.1051/epjconf/201714003056},\n\tabstract = {The geometric roughness at boundaries has a profound impact on the dynamics of granular flows. For a bumpy base made of fixed particles, two major factors have been separately studied in the literature, namely, the size and spatial distribution of base particles. A recent work (Jing et al. 2016) has proposed a roughness indicator $R_a$, which combines both factors for any arbitrary bumpy base comprising equally-sized spheres. It is shown in mono-disperse flows that as $R_a$ increases, a transition occurs from slip ($R_a$ < 0.51) to non-slip ($R_a$ > 0.62) conditions. This work focuses on such a phase transition in bi-disperse flows, in which $R_a$ can be a function of time. As size segregation takes place, large particles migrate away from the bottom, leading to a variation of size ratio between flow- and base-particles. As a result, base roughness $R_a$ evolves with the progress of segregation. Consistent with the slip/non-slip transition in mono-disperse flows, basal sliding arises at low values of $R_a$ and the development of segregation might be affected; when $R_a$ increases to a certain level ($R_a$ > 0.62), non-slip condition is respected. This work extends the validity of $R_a$ to bi-disperse flows, which can be used to understand the geometric boundary effect during segregation.},\n\turldate = {2017-07-16},\n\tbooktitle = { {EPJ} {Web} of {Conferences}},\n\tauthor = {Jing, L. and Kwok, C. Y. and Leung, Y. F. and Sobral, Y. D.},\n\tyear = {2017},\n\tpages = {03056}\n}\n\n
\n
\n\n\n
\n The geometric roughness at boundaries has a profound impact on the dynamics of granular flows. For a bumpy base made of fixed particles, two major factors have been separately studied in the literature, namely, the size and spatial distribution of base particles. A recent work (Jing et al. 2016) has proposed a roughness indicator $R_a$, which combines both factors for any arbitrary bumpy base comprising equally-sized spheres. It is shown in mono-disperse flows that as $R_a$ increases, a transition occurs from slip ($R_a$ < 0.51) to non-slip ($R_a$ > 0.62) conditions. This work focuses on such a phase transition in bi-disperse flows, in which $R_a$ can be a function of time. As size segregation takes place, large particles migrate away from the bottom, leading to a variation of size ratio between flow- and base-particles. As a result, base roughness $R_a$ evolves with the progress of segregation. Consistent with the slip/non-slip transition in mono-disperse flows, basal sliding arises at low values of $R_a$ and the development of segregation might be affected; when $R_a$ increases to a certain level ($R_a$ > 0.62), non-slip condition is respected. This work extends the validity of $R_a$ to bi-disperse flows, which can be used to understand the geometric boundary effect during segregation.\n
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\n \n\n \n \n \n \n \n \n Basal effect in mono- and bi-disperse chute flows.\n \n \n \n \n\n\n \n Jing, L.; Kwok, C. Y.; Leung, Y. F.; and Sobral, Y. D.\n\n\n \n\n\n\n In Li, X.; Feng, Y.; and Mustoe, G., editor(s), Proceedings of the 7th International Conference on Discrete Element Methods, volume 188, pages 671–678, Singapore, 2017. Springer Singapore\n \n\n\n\n
\n\n\n\n \n \n \"BasalPaper\n  \n \n\n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
\n 
@inproceedings{li_basal_2017,\n\taddress = {Singapore},\n\ttitle = {Basal effect in mono- and bi-disperse chute flows},\n\tvolume = {188},\n\tisbn = {978-981-10-1925-8 978-981-10-1926-5},\n\turl = {http://link.springer.com/10.1007/978-981-10-1926-5_69},\n\turldate = {2017-01-20},\n\tbooktitle = {Proceedings of the 7th {International} {Conference} on {Discrete} {Element} {Methods}},\n\tpublisher = {Springer Singapore},\n\tauthor = {Jing, Lu and Kwok, C. Y. and Leung, Y. F. and Sobral, Yuri D.},\n\teditor = {Li, Xikui and Feng, Yuntian and Mustoe, Graham},\n\tyear = {2017},\n\tpages = {671--678},\n\tabstract = {\n\tThe basal condition for granular chute flows is assumed rough and non-slip in experimental and numerical studies. In mono-disperse flows, a rough base is usually constructed by gluing/fixing a layer of particles that is similar or identical to the flowing particles. However, the base condition is not so clear in bi-disperse flows, where size segregation changes the relative basal roughness. In this paper, basal effect is studied in both mono- and bi-disperse chute flows. Different size ratios are adopted to understand how size segregation affects the basal condition and velocity profile in the steady, fully developed state. It is found that considerable sliding may arise as large particles stay in contact with the base, and it may affect the development of segregation. The velocity profile at the steady state is different due to the occurrence of segregation. In addition, sensitivity analyses show that the basal effect is independent of the sample size and contact parameters.\n\t}\n}\n\n
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\n The basal condition for granular chute flows is assumed rough and non-slip in experimental and numerical studies. In mono-disperse flows, a rough base is usually constructed by gluing/fixing a layer of particles that is similar or identical to the flowing particles. However, the base condition is not so clear in bi-disperse flows, where size segregation changes the relative basal roughness. In this paper, basal effect is studied in both mono- and bi-disperse chute flows. Different size ratios are adopted to understand how size segregation affects the basal condition and velocity profile in the steady, fully developed state. It is found that considerable sliding may arise as large particles stay in contact with the base, and it may affect the development of segregation. The velocity profile at the steady state is different due to the occurrence of segregation. In addition, sensitivity analyses show that the basal effect is independent of the sample size and contact parameters. \n
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\n  \n 2016\n \n \n (1)\n \n \n
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\n \n\n \n \n \n \n \n \n Experimental and numerical study of depositional mechanism of mudflow.\n \n \n \n \n\n\n \n Jing, L.; Kwok, C. Y.; Leung, Y. F.; Zhang, Z.; and Dai, L.\n\n\n \n\n\n\n In Feng, X.; and Yue, Z. Q., editor(s), Proceedings of International Geotechnics Symposium cum International Meeting of CSRME 14th Biennial National Congress, Hong Kong, 2016. \n \n\nBest Paper Award for Young Researchers.\n\n
\n\n\n\n \n \n \"ExperimentalSlides\n  \n \n\n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
\n 
@inproceedings{jing_experimental_2016,\n\taddress = {Hong Kong},\n\ttitle = {Experimental and numerical study of depositional mechanism of mudflow},\n\turlSlides = {http://www.igscsrm.hku.hk/pdf/presentedpdfs/Paper28-Jing.pdf},\n\tabstract = {\n\t\t<p>Mudflows tend to deposit after a rapid evolution on the steep channel down hillside. The large runout distance and deposit area are crucial concerns of geotechnical and geological engineers. In the rheological point of view, mudflows are non-Newtonian viscoplastic fluids which behave like a solid until submitted to a higher stress than the yield strength. Upon yielding, flow takes place and the flow behavior is described by viscosity. How viscosity and yield stress control the deposition of mudflows remains yet unclear due to the difficulties of performing large-scale experiments and scaling over a wide range of length scales.</p>\n\t\t<p>In this work, scaling of rheological parameters are proposed in a dimensional analysis. It is successfully used in numerical simulations to bridge the depositional behaviors of mudflows at different scales. The numerical modeling with Bingham and Herschel-Bulkley models are validated against small-scale flume experiments. The depositional mechanism of mudflows is associated with yield stress and viscosity. It is found that a deposition of slurry relevant to natural mudflows has the following features: (i) fast runout and stoppage due to relatively low viscosity; (ii) elongated shape due to fast runout (more stream-wise spreading than lateral spreading); (iii) remains stuck on the channel and steep edges due to high yield stress; (iv) flat deposit surface due to the effect of yield stress.</p>},\n\tbooktitle = {Proceedings of {International} {Geotechnics} {Symposium} cum {International} {Meeting} of {CSRME} 14th {Biennial} {National} {Congress}},\n\tauthor = {Jing, L. and Kwok, C. Y. and Leung, Y. F. and Zhang, Z. and Dai, L.},\n\teditor = {Feng, Xiating and Yue, Zhongqi Quentin},\n\tyear = {2016},\n\tbibbase_note = {<span style="color: #66afff">Best Paper Award for Young Researchers.</span>}\n}\n
\n
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Mudflows tend to deposit after a rapid evolution on the steep channel down hillside. The large runout distance and deposit area are crucial concerns of geotechnical and geological engineers. In the rheological point of view, mudflows are non-Newtonian viscoplastic fluids which behave like a solid until submitted to a higher stress than the yield strength. Upon yielding, flow takes place and the flow behavior is described by viscosity. How viscosity and yield stress control the deposition of mudflows remains yet unclear due to the difficulties of performing large-scale experiments and scaling over a wide range of length scales.

In this work, scaling of rheological parameters are proposed in a dimensional analysis. It is successfully used in numerical simulations to bridge the depositional behaviors of mudflows at different scales. The numerical modeling with Bingham and Herschel-Bulkley models are validated against small-scale flume experiments. The depositional mechanism of mudflows is associated with yield stress and viscosity. It is found that a deposition of slurry relevant to natural mudflows has the following features: (i) fast runout and stoppage due to relatively low viscosity; (ii) elongated shape due to fast runout (more stream-wise spreading than lateral spreading); (iii) remains stuck on the channel and steep edges due to high yield stress; (iv) flat deposit surface due to the effect of yield stress.

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\n  \n 2015\n \n \n (1)\n \n \n
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\n \n\n \n \n \n \n \n \n Discrete element modelling of grain size segregation in bi-disperse granular flows down chute.\n \n \n \n \n\n\n \n Jing, L.; Kwok, C. Y.; and Leung, Y. F.\n\n\n \n\n\n\n In International Conference on Particle-Based Methods, Fundamentals and Applications, Barcelona, Spain, 2015. \n \n\n\n\n
\n\n\n\n \n \n \"DiscretePaper\n  \n \n\n \n\n \n link\n  \n \n\n bibtex\n \n\n \n  \n \n abstract \n \n\n \n\n \n \n \n \n \n \n \n\n  \n \n \n\n\n\n
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@inproceedings{jing_discrete_2015,\n\taddress = {Barcelona, Spain},\n\ttitle = {Discrete element modelling of grain size segregation in bi-disperse granular flows down chute},\n\turl = {http://hub.hku.hk/handle/10722/213642},\n\turldate = {2015-10-06},\n\tbooktitle = {International {Conference} on {Particle}-{Based} {Methods}, {Fundamentals} and {Applications}},\n\tauthor = {Jing, L. and Kwok, C. Y. and Leung, Y. F.},\n\tyear = {2015},\n\tabstract = {\n\tThree-dimensional DEM simulations of size segregation in granular flows down chute are presented. Different cubic bi-disperse samples are generated by pluviation, on the rough base formed by randomly placed particles. Periodic boundaries are applied to the flow direction and the two sides. Parametrical studies involving slope angle, width, volume fraction, and coefficient of friction are systemically performed. In all presented cases, steady, fully developed (SFD) state is achieved, where the kinetic energy and fractional volume distribution remain constant. From the macroscopic view, segregations are completed in the SFD state with slightly different extents and a thick layer of pure coarse grains appears on the top of the flow. The profiles of volume fractions are calculated and presented by shear layers. In addition, the trajectories of individual particles are tracked and analysed, showing clearly the contact conditions and shear history experienced by individual particles. It is found that the connectivity of small particles is generally at a lower level than that of the large ones, indicating a high probability of small particles dropping into voids under gravity is higher. On the other hand, the large particles experience a significant increase of connectivity as they migrate through the layer of small particles.\n\t}\n}\n\n
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\n Three-dimensional DEM simulations of size segregation in granular flows down chute are presented. Different cubic bi-disperse samples are generated by pluviation, on the rough base formed by randomly placed particles. Periodic boundaries are applied to the flow direction and the two sides. Parametrical studies involving slope angle, width, volume fraction, and coefficient of friction are systemically performed. In all presented cases, steady, fully developed (SFD) state is achieved, where the kinetic energy and fractional volume distribution remain constant. From the macroscopic view, segregations are completed in the SFD state with slightly different extents and a thick layer of pure coarse grains appears on the top of the flow. The profiles of volume fractions are calculated and presented by shear layers. In addition, the trajectories of individual particles are tracked and analysed, showing clearly the contact conditions and shear history experienced by individual particles. It is found that the connectivity of small particles is generally at a lower level than that of the large ones, indicating a high probability of small particles dropping into voids under gravity is higher. On the other hand, the large particles experience a significant increase of connectivity as they migrate through the layer of small particles. \n
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\n \n\n \n \n \n \n \n A coupled CFD-DEM model for fluid-particle flows with free surface: formulation and validation.\n \n \n \n\n\n \n Jing, L.; Kwok, C. Y.; and Leung, Y. F.\n\n\n \n\n\n\n In Geomechanics from micro to macro, Cambridge; the UK, 2014. Taylor & Francis Group\n \n\n\n\n
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@inproceedings{jing_coupled_2014,\n\taddress = {Cambridge; the UK},\n\ttitle = {A coupled {CFD}-{DEM} model for fluid-particle flows with free surface: formulation and validation},\n\tisbn = {978-1-138-02707-7},\n\tlanguage = {English},\n\tbooktitle = {Geomechanics from micro to macro},\n\tpublisher = {Taylor \\& Francis Group},\n\tauthor = {Jing, Lu and Kwok, C. Y. and Leung, Y. F.},\n\tyear = {2014},\n\tabstract = {\n\tA coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) model is presented for fluid-particle flows with free fluid surface. The fluid flow is modeled by solving the locally averaged Navier-Stokes equations, and the particle motions are captured separately in the DEM. Fluid-particle interactions are taken into consideration by exchanging necessary information between the CFD and the DEM. A numerical solver, referred to as cfdemSolverVOF in this study, is developed to capture the dynamics of the free fluid surface within the CFD-DEM framework. This is achieved by applying an advection equation to solve the volume fraction of the liquid in each fluid cell, in the spirit of the Volume of Fluid (VOF) method. Different components of the developed numerical solver are verified and validated in the dam break case and sedimentation of particle tests. The numerical predictions agree well with the analytical/empirical solutions.\n\t}\n}\n\n
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\n A coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) model is presented for fluid-particle flows with free fluid surface. The fluid flow is modeled by solving the locally averaged Navier-Stokes equations, and the particle motions are captured separately in the DEM. Fluid-particle interactions are taken into consideration by exchanging necessary information between the CFD and the DEM. A numerical solver, referred to as cfdemSolverVOF in this study, is developed to capture the dynamics of the free fluid surface within the CFD-DEM framework. This is achieved by applying an advection equation to solve the volume fraction of the liquid in each fluid cell, in the spirit of the Volume of Fluid (VOF) method. Different components of the developed numerical solver are verified and validated in the dam break case and sedimentation of particle tests. The numerical predictions agree well with the analytical/empirical solutions. \n
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