[Nature Comms] Scalable high yield exfoliation for monolayer nanosheets

 

Scalable high yield exfoliation for monolayer nanosheets

https://www.nature.com/articles/s41467-022-35569-8

A Nature Comms paper is published. Happy New Year!

Effect of particle shape on raceway size: an extensive study

 

Effect of particle shape on raceway size and pressure drop in a blast furnace: Experimental, numerical and theoretical analyses

Reference

Wei, G., Zhang, H., An, X. and Hou, Q., 2022. Effect of particle shape on raceway size and pressure drop in a blast furnace: Experimental, numerical and theoretical analyses. Advanced Powder Technology, 33, 103455.

Highlights

•

Raceway size and pressure drop are investigated by physical experiments employing different non-spherical particles.

•

Influence of aspect ratio on the raceway evolution mechanisms is discussed by using CFD-DEM.

•

Theoretical predictive model of raceway size is improved by considering the effect of particle shape.

1434 Google Scholar citations

All my publications received another 200 more citations with an H-index of 18. 

One Highly Cited Paper in Energy & Environmental Science (Impact Factor: 38.532)

Y. Xia, Q.F. Hou, H. Jubaer, Y. Li, Y. Kang, S. Yuan, H.Y. Liu, M.W. Woo, L. Zhang, L. Gao, H.T. Wang, X.W. Zhang. Spatially isolating salt crystallisation from water evaporation for continuous solar steam generation and salt harvesting, Energy & Environmental Science, 12 (2019) 1840-1847. (Highly Cited Paper)

PS: After I wrongly updated the previous post in the series (GS =1203, Jan 2021), I found it is better to update the same post and modify the post date.

<Don’t be a prig in peer review> and my thoughts

Read this article from Nature today. I do have some thoughts to share as I have reviewed 300+ times for international journals and published 60+ refereed journals (approximately received 120+ reviews). These points should be helpful for authors seeking publications. One might also feel overloaded with reviewer requests.

You should keep the timeframe requested by a Journal when you accept a request. The following points could be considered when you provide a referee report.

• Proper training for peer-review

I received such training when I did my Ph.D. at UNSW Australia with Professor Aibing Yu. The document provided by the Americal Physical Society is very helpful. The following are the Guidelines provided by Physical Review E (https://journals.aps.org/pre/referees/guidelines-for-referees).

Guidelines for Referees

Referees play a crucial role in evaluating manuscripts submitted to the Physical Review journals. Physical Review editors work closely with referees to apply the acceptance criteria stringently and to act promptly in accepting or rejecting manuscripts. Your active collaboration as a referee is central to the success of the journals.

Invitation to Review

The email invitation to review includes links to accept or decline. Before you accept, please ensure that the manuscript content is close enough to your area of expertise to allow you to provide useful input and a prompt review. If that is not the case, please decline; your suggestions for alternate reviewers are welcomed.

Confidentiality

All materials associated with the review process are confidential, including the manuscript, Supplemental Material, author-provided material, referee reports, and other correspondence. These materials must remain confidential when you consult with colleagues or invite them to write a joint report. We ask that you include the names and contact information of any colleagues who help in writing the report. When you are reviewing a manuscript, please do not initiate discussions with the author(s); instead, please contact the editors with your inquiry.

It is vitally important for reviewers to disclose any conflicts of interest to the editors. Please let them know if you have a direct competitive, collaborative, or other relationship with an author that could preclude your objective evaluation of the manuscript. It is unethical for you to use the content of a manuscript sent to you for review for your own scientific purposes. The Physical Review journals are members of the Committee on Publication Ethics and follow its guidelines.

Reviewing the Manuscript and Writing the Report

The following guidelines are an aid to help when reviewing the manuscript. Read the referral letter carefully; there may be editor comments and questions, and/or reference material and previous correspondence sent with the referral. When writing your report, use clear, simple wording and avoid overly negative or polemical comments.

We suggest dividing your review into three parts: (I) Comments intended for both the author(s) and the editors; (II) Recommendation; (III) Comments to the editors only.

Comments intended for both the author(s) and the editors:

• Briefly summarize the manuscript. The summary could include a statement on the key results and how they add to the field.
• Assess the originality and significance of the results.
• Assess the technical quality and scientific rigor of the manuscript.
• Is the work well executed and technically correct?
• Are the models or approximations used sufficiently justified?
• Are the main conclusions or claims well supported?
• Is the section for which this manuscript is being considered (Regular Article, Rapid Communication, or Comment) the right venue for this work? Be aware that some sections have length limits.
• If submitted as a Rapid Communication, does the work’s quality and importance justify the special handling associated with the section?
• Assess the manuscript’s presentation.
• Are the title and abstract informative, concise, and clear?
• Is the manuscript well organized and clearly written?
• Is the description of the technical content sufficiently comprehensive?
• Are the references to the literature appropriate and adequate?
• Does the content of the manuscript justify its length? Please be specific as to how and where the manuscript could be expanded or shortened.
• Are the figures and tables clear, useful, and suitably summarized in the captions? Is there duplication from previous publications?
• Assess the content and quality of the Supplemental Material. Is the information included supplemental or essential for understanding the manuscript? Should any of it be included in the main text?

Recommendation:
Your report should include a recommendation to accept, revise and reconsider, or reject the manuscript. Please provide reasons for your recommendation.

Comments intended for the editors only:
When submitting your report, you will be presented with a table of checkboxes where you can summarize your overall view of the manuscript for the editors. Here you can indicate your recommendation on accepting or rejecting the manuscript, and, if appropriate, suggest that the paper be transferred to another Physical Review journal or submitted elsewhere. This section is where you may include confidential remarks for the editor. These comments may include your thoughts on why the paper is right or wrong for the particular journal, reasons behind your recommendation, or other information you feel would be useful.

• Critical, but kind and courteous

One published paper should enrich the knowledge pool. Critical is important for scientific publication. You certainly do not want to waste your time searching for useful points from many trash papers. Thus, a reviewer is asked to evaluate the originality of a paper and the significance of the results. One often compares the contributions from different papers and judges the originality and the significance. Thus a comprehensive and unbiased literature review is necessary and helpful.

A referee, when question the originality, should provide evidence supported comments, e.g., with published papers with similar claims.

The presentation often comes after the originality and significance. This depends on the journal policy. Some journals will reject such low-quality papers straight away. A responsible referee will give opportunities for authors to revise once the paper passed the screening of the journal's editorial office. However, personally, I do not have positive attitude to a poorly-presented paper. The authors should try to provide a better presentation through a few rounds of revision. 

• Constructive, not subjective

A reviewer should provide tangible comments objectively so that the authors know how to response. Regarding this aspect, the authors are suggested to take a second thought of the critical comments provided, do not just feel annoyed. Ofter, a reviewer's comment is based on your manuscript, and there is a high possibility that some points were not clear.

A reviewer should avoid untangible and subjective comments, particularly on personality.

Summary 

Some key rules should be followed for conducting peer review. However, I know it is hard to be 100% objective. That is why scientific journals often provide opportunities for the authors to provide a Reply for some rounds.

Try to provide kindly critical, evidence-based, and science promoting comments!

Reference

https://www.nature.com/articles/d41586-020-02512-0?utm_source=twitter&utm_medium=social&utm_content=organic&utm_campaign=NGMT_USG_JC01_GL_Nature

1001 Google Scholar citations

1001 Google Scholar citations

All my publications received 1000+ citations with an H-index of 17. Since the citation number increases rapidly, I will update for every 200 more citations.

Newly published papers

List of papers in 2020 up to now. You may also find my full publications here.

[1] Y. L. Wu, Q. F. Hou, A. B. Yu. Linking discrete particle simulation to continuum properties of the gas fluidization of cohesive particles. AIChE Journal In Press (2020) e16944.
[2] Y. L. Wu, Q. F. Hou, K. J. Dong, A. B. Yu. Effect of packing method on packing formation and the correlation between packing density and interparticle force. Particuology 48 (2020) 170-181.
[3] L. Massaro Sousa, M. C. Ferreira, Q. F. Hou, A. B. Yu. Feeding Spent Coffee Grounds into Reactors: CFD Modeling of a Non-Mechanical Spouted Bed Type Feeder. Waste Management 109 (2020) 161-170.
[4] L. Massaro Sousa, M. C. Ferreira, Q. F. Hou, A. B. Yu. Feeding Spent Coffee Ground Powders with a Non-Mechanical L-valve: Experimental Analysis and CFD Simulation. Powder Technology 360 (2020) 1055-1066.
[5] F. Marchelli, Q. F. Hou, B. Bosio, E. Arato, A. B. Yu. Comparison of different drag models in CFD-DEM simulations of spouted beds. Powder Technology 360 (2020) 1253-1270.
[6] X. Li, Q. F. Hou, K. J. Dong, R. P. Zou, A. B. Yu. Promote cohesive solid flow in a screw feeder with new screw designs. Powder Technology 361 (2020) 248-257.
[7] Q. F. Hou, Z. Y. Zhou, J. S. Curtis, A. B. Yu. Statistical analysis of monodispersed coarse particle motion in a gas-fluidized bed. Powder Technology 363 (2020) 107-111.
[8] Q. F. Hou, D. Y. E, S. B. Kuang, A. B. Yu. A Transient Discrete Element Method-Based Virtual Experimental Blast Furnace Model. Steel Research International (2020) 2000071.
[9] Q. F. Hou, D. Y. E, S. B. Kuang, A. B. Yu. A process scaling approach for CFD-DEM modelling of thermochemical behaviours in moving bed reactors. Fuel Processing Technology 202 (2020) 106369.
[10] M. L. He, N. Wang, Q. F. Hou, M. Chen, H. Y. Yu. Coalescence and sedimentation of liquid Iron droplets during smelting reduction of converter slag with mechanical stirring. Powder Technology 362 (2020) 550-558.
[11] J. X. Cui, Q. F. Hou, Y. S. Shen. CFD-DEM study of coke combustion in the raceway cavity of an ironmaking blast furnace. Powder Technology 362 (2020) 539-549.
[12] J. Azmir, Q. F. Hou, A. B. Yu. CFD-DEM study of the effects of food grain properties on drying and shrinkage in a fluidised bed. Powder Technology 360 (2020) 33-42.
[13] S. Arifuzzaman, K. J. Dong, Q. F. Hou, H. P. Zhu, Q. H. Zeng. Explicit contact force model for superellipses by Fourier transform and application to superellipses packing. Powder Technology 361 (2020) 112-123.

Read this Nature paper about airborne particles if you care about your every breath

NEWS AND VIEWS  13 MAY 2020

Airborne particles might grow fast in cities

By Hugh Coe

Nanoscale particles have been observed to form and grow in the atmospheres of many cities, contradicting our understanding of particle-formation processes. Experiments now reveal a possible explanation for this mystery.

(发展中国家必经之路吗？）

Article

Rapid growth of new atmospheric particles by nitric acid and ammonia condensation

Wang, M. et al. Nature 581, 184–189 (2020).

New-particle formation is a major contributor to urban smog1,2, but how it occurs in
cities is often puzzling3. If the growth rates of urban particles are similar to those found in
cleaner environments (1–10 nanometres per hour), then existing understanding
suggests that new urban particles should be rapidly scavenged by the high concentration
of pre-existing particles. Here we show, through experiments performed under
atmospheric conditions in the CLOUD chamber at CERN, that below about +5 degrees
Celsius, nitric acid and ammonia vapours can condense onto freshly nucleated particles
as small as a few nanometres in diameter. Moreover, when it is cold enough (below −15
degrees Celsius), nitric acid and ammonia can nucleate directly through an acid–base
stabilization mechanism to form ammonium nitrate particles. Given that these vapours
are often one thousand times more abundant than sulfuric acid, the resulting particle
growth rates can be extremely high, reaching well above 100 nanometres per hour.
However, these high growth rates require the gas-particle ammonium nitrate system to
be out of equilibrium in order to sustain gas-phase supersaturations. In view of the strong
temperature dependence that we measure for the gas-phase supersaturations, we
expect such transient conditions to occur in inhomogeneous urban settings, especially
in wintertime, driven by vertical mixing and by strong local sources such as traffic. Even
though rapid growth from nitric acid and ammonia condensation may last for only a few
minutes, it is nonetheless fast enough to shepherd freshly nucleated particles through
the smallest size range where they are most vulnerable to scavenging loss, thus greatly
increasing their survival probability. We also expect nitric acid and ammonia nucleation
and rapid growth to be important in the relatively clean and cold upper free troposphere,
where ammonia can be convected from the continental boundary layer and nitric acid is
abundant from electrical storms4,5.

（不是应该由中国科学家领衔吗？；），还好有中国单位参与 ：））

Feeding Spent Coffee Grounds into Reactors: TFM Simulation of a Non-Mechanical Spouted Bed Type Feeder

Link for 50 days' free access https://authors.elsevier.com/a/1b2ZF,LlFP9xwn

Feeding Spent Coffee Grounds into Reactors:

TFM Simulation of a Non-Mechanical Spouted Bed Type Feeder

Lucas Massaro Sousa^{1, 2}, Maria C. Ferreira², Qinfu Hou^[1]*and Aibing Yu^{1, 3}

¹ARC Research Hub for Computational Particle Technology, Chemical Engineering Department, Monash University, Clayton, VIC 3800, Australia

²Drying Center for Pastes, Suspensions, and Seeds, Chemical Engineering Department, Federal University of São Carlos, P.O. Box 676, 13565-905 São Carlos, Brazil

³Centre for Simulation and Modelling of Particulate Systems, Southeast University−Monash University Joint Research Institute, Suzhou 215123, PR China

* Corresponding author. E-mail address: qinfu.hou@monash.edu

ABSTRACT

Due to the increasing coffee production, Spent Coffee Grounds’ (SCGs) generation has grown dramatically, hence appropriate management of this solid biomass waste is imperative. SCGs can be used as feedstocks for renewable energy and fuel generation provided that a stable feeding of powders to reactors is maintained. Recently, a non-mechanical spouted bed feeder proved itself an excellent alternative in feeding SCGs to a pilot-scale circulating fluidized bed reactor. Nonetheless, further studies are necessary for the feeder’s implementation in commercial applications. Here the feeding of SCGs with the spouted bed feeder is addressed by using Computational Fluid Dynamics. Firstly, a Two-Fluid Model (TFM) is validated against experimental data, and then the effects of five operating and design parameters were analyzed aiming at improving the handling of SCGs. The solids flowrate (W_S) in the reactor could be stably controlled from 4 to 30 g/s depending on the settings. The feeder performance is enhanced by operating it under high gas flowrate (Q), high entrainment length (z), and high mass of solids in the feeder (H_S). Using feeders with low cone angle (γ) or reactors with large diameter (D_R) increases W_S, which is appealing for the operation of medium-to large-scale units. The proposed TFM is a cost-effective tool for implementing spouted bed feeders in commercial applications. With the feeder coupled to the process, SCGs are treated continuously in the reactor for energy generation, thus reducing the disposal problems associated with this waste and improving the management of SCGs globally.

Keywords: feeding device; spent coffee grounds; two-fluid model; spouted bed; CFD.

A Transient Discrete Element Method-Based Virtual Experimental Blast Furnace Model

Hou, Q.F., E, D.Y., Kuang, S.B., Yu, A.B., 2020. A Transient Discrete Element Method-Based Virtual Experimental Blast Furnace Model. Steel Research International, 2000071. https://doi.org/10.1002/srin.202000071

A Transient Discrete Element Method‐Based Virtual Experimental Blast Furnace Model

Qinfu Hou  Dianyu E  Shibo Kuang  Aibing Yu

Abstract

Intensive heat and mass transfer between continuum fluids and discrete particulate materials occur in the current working‐horse blast furnace (BF) ironmaking process. To optimize the operation, its energy efficiency and sustainability, discrete particle models are very helpful when they are incorporated with flow, heat and mass transfer, and chemical reaction models. Herein, a transient discrete element method‐based virtual BF model is developed through scaling. The scaled model simulates the process significantly faster and makes it practical to track the whole process of iron ore reduction from burden charge to the cohesive zone (CZ). The model is applied to an experimental BF and the predictions are tested against available experimental results and those of computational fluid dynamics models. The results demonstrate that the scaled virtual BF model can reasonably predict in‐furnace flow state, temperature distribution, iron ore reduction, and the characteristics of the CZ. The particle‐scale BF model provides detailed information of particle motion, temperature, and chemical reactions, enabling fundamental understanding and further optimization and control of the process. The scaled BF model can be extended to study the effects of raw material properties and operation parameters on BF performance.

Relevant publications:

Hou, Q.F., E, D.Y., Kuang, S.B., Yu, A.B., 2020. A process scaling approach for CFD-DEM modelling of thermochemical behaviours in moving bed reactors. Fuel Processing Technology 202, 106369.

Hou, Q.F., E, D.Y., Kuang, S.B., Li, Z.Y., Yu, A.B., 2017. DEM-based virtual experimental blast furnace: A quasi-steady state model. Powder Technology 314, 557-566.

888 Google Scholar citations and 100 citations for a paper

888 Google Scholar citations and 100 citations for a paper

Recently published papers:

Y. L. Wu, Q. F. Hou, A. B. Yu. Linking discrete particle simulation to continuum properties of the gas fluidization of cohesive particles. AIChE Journal, In Press (2020).

Abstract

Discrete particle simulation can explicitly consider interparticle forces and obtain microscopic properties of the fluidized cohesive particles, but it is computationally expensive. It is thus pivotal to link the microscopic discrete properties to the macroscopic continuum description of the system for large scale applications. This work studies the fluidization of cohesive particles through the coupled computational fluid dynamics and discrete element method (CFD-DEM). First, discrete CFD-DEM results show the increased particle cohesion leads to the severe particle agglomeration which affects the fluidization quality significantly. Then, continuum properties are attained by a weighted time-volume averaging method, showing that tensile pressure becomes significant as particle cohesion increases. By incorporating the Rumpf correlation into the solid pressure equation, the tensile pressure could be predicted consistently with the averaged CFD-DEM results for different particle cohesion. Finally, those overall steady averaged properties of the bed are obtained for understanding the general macroscopic properties of the system.

Keywords: fluidization, CFD-DEM, averaging method, cohesive particle, agglomeration

Q. F. Hou, D. Y. E, S. B. Kuang, A. B. Yu. A process scaling approach for CFD-DEM modelling of thermochemical behaviours in moving bed reactors. Fuel Processing Technology In Press (2020).

Abstract

Intensive heat and mass transfer between continuum fluids and discrete particulate materials plays a critical role in many chemical reactors. The residence and chemical reactions of particulate materials could span over hours. To understand and improve the operation of these reactors, discrete particle models are very helpful and computationally demanding. Different to the previous coarse grain model in reducing computational cost by reducing total particle number with large representative particles, a scaling approach by changing process parameters and thus the time scale is established to significantly reduce computational cost for the combined computational fluid dynamics (CFD) and discrete element method (DEM) modelling of moving bed reactors. The scaled model is first derived based on the governing equations of mass, momentum and energy for two-phase flow and then applied to a moving bed reactor. The results in terms of flow, heat and mass transfer and chemical reactions with different time scaling factors demonstrate that two-order acceleration in terms of computational time can be achieved while reliably representing the same physical process. The possible use of the scaling approach to other systems is discussed. The scaling approach represents a critical step forward towards establishing virtual real-time thermochemical reactors with discrete particle models.

Keywords: CFD-DEM; Scaling; Heat and mass transfer; Chemical reaction; Moving bed reactor

[Paper in Press] Comparison of different drag models in CFD-DEM simulations of spouted beds

This is a paper published in Powder Technology with a short term visitor Filippo Marchelli from Italy.

https://doi.org/10.1016/j.powtec.2019.10.058

Comparison of different drag models in CFD-DEM simulations of spouted beds

Filippo Marchelli,^1,2 Qinfu Hou,²* Barbara Bosio,³ Elisabetta Arato³ and Aibing Yu^2,4

¹Faculty of Science and Technology, Free University of Bozen-Bolzano, 39100 Bolzano, Italy

²ARC Research Hub for Computational Particle Technology, Department of Chemical Engineering, Monash University, Clayton, VIC 3800, Australia

³Process Engineering Research Team, Department of Civil, Chemical and Environmental Engineering, University of Genova, 16145 Genova, Italy

⁴Center for Simulation and Modelling of Particulate Systems, Southeast University - Monash University Joint Research Institute, Suzhou 215123, PR China

*Corresponding author. Email: Qinfu.Hou@monash.edu

Abstract

Spouted beds are commonly simulated through the Computational Fluid Dynamics – Discrete Element Method approach. The choice of the drag model is still a matter of debate, as they feature peculiar operative conditions. In this work, we simulated two spouted beds containing Geldart-D particles. We tested seven drag models: three are classic models, while four are developed through advanced computational techniques. The results indicate that the key variable is the ratio between the operative and the minimum spouting gas velocity (u/u_ms). At u=u_ms only the Gidaspow model can always predict fluidisation, but at low u/u_ms values the Beetstra model is the best compromise. For higher values, the Rong and Di Felice models behave better, while the others overestimate the particles’ velocity. These results can be useful to identify the best performing model and show there is a need for more appropriate models for spouted beds.

Keywords: Eulerian-Lagrangian approach, fluidisation, gas-solid exchange coefficient, spouted bed, user-defined function.

Google Scholar citations 800+, H-index 15

Update: Another 100+ citations

[Paper Accepted] Feeding spent coffee ground powders with a non-mechanical L-valve: Experimental analysis and TFM simulation

https://doi.org/10.1016/j.powtec.2019.11.005

Feeding Spent Coffee Ground Powders with a Non-Mechanical L-valve: Experimental Analysis and TFM Simulation

Lucas Massaro Sousa^{1, 2}, Maria C. Ferreira², Qinfu Hou^[1]* and Aibing Yu^{1, 3}

¹ARC Research Hub for Computational Particle Technology, Chemical Engineering Department, Monash University, Clayton, VIC 3800, Australia

²Drying Center for Pastes, Suspensions, and Seeds, Chemical Engineering Department, Federal University of São Carlos, P.O. Box 676, 13565-905 São Carlos, Brazil

³Centre for Simulation and Modelling of Particulate Systems, Southeast University−Monash University Joint Research Institute, Suzhou 215123, PR China

ABSTRACT

A better understanding of feeding operations is pressing for value-added processing of waste biomass powders. This paper examines the feeding of Spent Coffee Grounds (SCGs) using a non-mechanical L-valve both experimentally and numerically. L-valve provides stable solids feeding, showing different flow regimes. Powders’ height in the standpipe must be monitored to guarantee smooth operations with the valve, and the data for SCGs differ significantly from those reported for glass and sand powders. A new correlation to predict the solids flowrate from simple pressure measurements was proposed for valve operating under high air flowrates. For low to medium air flowrates, a two-fluid model (TFM) was proposed and validated. The SCGs’ flowrate in the feeder was accurately predicted by the TFM and the correlation. Furthermore, key information for the design of L-valves was obtained from the TFM simulation. The findings are useful for producing renewable thermal energy and fuels with biomass SCGs.

Keywords: non-mechanical feeder; biomass; two-fluid model; friction packing limit; restitution coefficient

---

* Corresponding author. E-mail address: qinfu.hou@monash.edu (Qinfu Hou).

Outstanding Poster Award on our averaging method study in 1st International Conf on Energy and Environment

It is a great honor to receive an Outstanding Poster Award on our averaging method work.

Refs:

1. Q. F. Hou, Z. Y. Zhou, J. S. Curtis, A. B. Yu. How to generate valid local quantities of particle-fluid flows for establishing constitutive relations. AIChE Journal, 65 (2019) e16690.
2. Y. L. Wu, Q. F. Hou, A. B. Yu. Linking discrete particle simulation to continuum properties of the gas fluidization of cohesive particles. Submitted (2019).

[Paper accepted] Promote cohesive solid flow in a screw feeder with new screw designs

This paper provides solutions to mitigate the effect of bridging/arching for cohesive and noncohesive solid flow in a screw feeder in connection to our previous paper on the underlying mechanisms.

Q. F. Hou, K. J. Dong, A. B. Yu. DEM study of the flow of cohesive particles in a screw feeder. Powder Technology 256 (2014) 529-539.

https://qfhou.blogspot.com/2014/01/powder-technology-paper-online-dem.html

Promote cohesive solid flow in a screw feeder with new screw designs

Xin Li,^a Qinfu Hou,^a[1] Kejun Dong,^b Ruiping Zou^a and Aibing Yu^a,c

^aARC Research Hub for Computational Particle Technology, Department of Chemical Engineering, Monash University, Clayton, VIC 3800, Australia

^bCenter for Infrastructure Engineering, Western Sydney University, Penrith, NSW 2751, Australia

^cCenter for Simulation and Modelling of Particulate Systems, Southeast University - Monash University Joint Research Institute, Suzhou 215123, PR China

Abstract

Screw feeders are widely used in industries to transfer granular materials at relatively precise rates. Often, granular materials can have a certain level of cohesiveness which can significantly affect the transport among other factors. The critical mechanism that can stop granular flow is the formation of bridge or arching. In this work, novel screw designs are proposed to promote cohesive solid flows in a screw feeder. First, through a numerical model based on the discrete element method, it is demonstrated that the new designs are effective. Then, the underlying mechanism is analyzed both macroscopically in terms of particle flow pattern, velocity field and the motion of screw and microscopically in terms of temporal and spatial variations of contact force between particles. It is revealed that the new screw designs can induce a bulk perturbation to the granular material in the bin in addition to the existing local perturbation by the screw blade. Thus, the formation of bridge can be deterred, and the cohesive solid flow is promoted. It is suggested that such designs could also be effective to non-cohesive granular materials. Further study should be conducted to optimize the designs.

Keywords: screw feeder; cohesive granular materials; new screw blade design; perturbation

---

[1]Corresponding author. Email: qinfu.hou@monash.edu.

[Paper accepted] How to generate valid local quantities of particle-fluid flows for establishing constitutive relations

Q.F. Hou, Z.Y. Zhou, J.S. Curtis, A.B. Yu. How to generate valid local quantities of particle-fluid flows for establishing constitutive relations. AIChE Journal, Accepted (2019).

https://aiche.onlinelibrary.wiley.com/doi/10.1002/aic.16690

How to Generate Valid Local Quantities of Particle-fluid Flows for Establishing Constitutive Relations

Qinfu Hou,^1* Zongyan Zhou,¹ Jennifer S. Curtis² and Aibing Yu^1,3*

¹ARC Research Hub for Computational Particle Technology, Department of Chemical Engineering, Monash University, Clayton, VIC 3800, Australia

²College of Engineering, University of California at Davis, One Shields Ave, Davis, CA 95616, USA

³Centre for Simulation and Modelling of Particulate Systems, Southeast University - Monash University Joint Research Institute, Suzhou 215123, PR China

Abstract

There are continuum and discrete approaches to describe granular flows. A continuum approach relies on local average quantities which can be derived through an averaging method based on a discrete approach. But the selection of averaging domain and the validity of local quantities for constitutive relations are not well established, particularly for transient particle-fluid flows. Here, it is demonstrated that converged local quantities can be achieved on an averaging domain with proper spatial and temporal sizes. Furthermore, the relation between solid pressure and solid volume fraction is established, agreeing qualitatively to all the existing monotonic ones in the literature. But it is quantitatively different, showing a bifurcation at a high solid volume fraction, which is essentially linked to the variation of short and enduring contacts among particles with flow state and solid volume fraction. This bifurcation must be properly recognized in developing constitutive relations for granular materials.

Keywords: particle-fluid flow, fluidized beds, averaging method, constitutive relation, solid pressure

[The relations between solid pressure Ps and solid volume fraction εs in fluidized and moving beds. Scattered circle and triangular symbols are from the averaging method with Lt = 180 and Lp = 3. ]