Effect of geometric base roughness on size segregation

L. Jing; C. Y. Kwok; Y. F. Leung; Y. D. Sobral

doi:10.1051/epjconf/201714003056

Effect of geometric base roughness on size segregation

L. Jing
, C. Y. Kwok
, Y. F. Leung
, Y. D. Sobral

Research output: Journal Publications and Reviews › RGC 21 - Publication in refereed journal › peer-review

4 Citations (Scopus)

Abstract

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. © The Authors, published by EDP Sciences, 2017.

Original language	English
Article number	03056
Journal	EPJ Web of Conferences
Volume	140
DOIs	https://doi.org/10.1051/epjconf/201714003056
Publication status	Published - 30 Jun 2017
Externally published	Yes
Event	8th International Conference on Micromechanics on Granular Media, Powders and Grains 2017 - Montpellier, France Duration: 3 Jul 2017 → 7 Jul 2017

Bibliographical note

Publication details (e.g. title, author(s), publication statuses and dates) are captured on an “AS IS” and “AS AVAILABLE” basis at the time of record harvesting from the data source. Suggestions for further amendments or supplementary information can be sent to [email protected].

Funding

The work was supported by Research Grants Council of Hong Kong (Grant No. RGC/GRF 17203614), and the Research Institute for Sustainable Urban Development at The Hong Kong Polytechnic University, and FAP-DF, Brazil. This research is conducted in part using the research computing facilities and advisory services offered, by Information Technology Services, the University of Hong Kong.

Publisher's Copyright Statement

This full text is made available under CC-BY 4.0. https://creativecommons.org/licenses/by/4.0/

RGC Funding Information

RGC-funded

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title = "Effect of geometric base roughness on size segregation",

abstract = "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 Ra, which combines both factors for any arbitrary bumpy base comprising equally-sized spheres. It is shown in mono-disperse flows that as Ra increases, a transition occurs from slip (Ra < 0.51) to non-slip (Ra > 0.62) conditions. This work focuses on such a phase transition in bi-disperse flows, in which Ra 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 Ra evolves with the progress of segregation. Consistent with the slip/non-slip transition in mono-disperse flows, basal sliding arises at low values of Ra and the development of segregation might be affected; when Ra increases to a certain level (Ra > 0.62), non-slip condition is respected. This work extends the validity of Ra to bi-disperse flows, which can be used to understand the geometric boundary effect during segregation. {\textcopyright} The Authors, published by EDP Sciences, 2017.",

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AU - Jing, L.

AU - Kwok, C. Y.

AU - Leung, Y. F.

AU - Sobral, Y. D.

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N2 - 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 Ra, which combines both factors for any arbitrary bumpy base comprising equally-sized spheres. It is shown in mono-disperse flows that as Ra increases, a transition occurs from slip (Ra < 0.51) to non-slip (Ra > 0.62) conditions. This work focuses on such a phase transition in bi-disperse flows, in which Ra 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 Ra evolves with the progress of segregation. Consistent with the slip/non-slip transition in mono-disperse flows, basal sliding arises at low values of Ra and the development of segregation might be affected; when Ra increases to a certain level (Ra > 0.62), non-slip condition is respected. This work extends the validity of Ra to bi-disperse flows, which can be used to understand the geometric boundary effect during segregation. © The Authors, published by EDP Sciences, 2017.

AB - 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 Ra, which combines both factors for any arbitrary bumpy base comprising equally-sized spheres. It is shown in mono-disperse flows that as Ra increases, a transition occurs from slip (Ra < 0.51) to non-slip (Ra > 0.62) conditions. This work focuses on such a phase transition in bi-disperse flows, in which Ra 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 Ra evolves with the progress of segregation. Consistent with the slip/non-slip transition in mono-disperse flows, basal sliding arises at low values of Ra and the development of segregation might be affected; when Ra increases to a certain level (Ra > 0.62), non-slip condition is respected. This work extends the validity of Ra to bi-disperse flows, which can be used to understand the geometric boundary effect during segregation. © The Authors, published by EDP Sciences, 2017.

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Effect of geometric base roughness on size segregation

Abstract

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