Numerical Simulations of Particle Motions at Continuous Rotational Speed Changes in Horizontal Rotating Drums

Round 1

Reviewer 1 Report

Comments for author File: Comments.doc

Author Response

Dear reviewers, thank you for your careful review of this manuscript. Your comments are of great significance for the revision and improvement of this manuscript, which has been carefully analysed by the author's team and refined by the manuscript. The author team has provided thoughtful responses to each of your review comments, as detailed in the word document.

Author Response File: Author Response.docx

Reviewer 2 Report

The motion of binary particles in horizontal rotating drums is investigated via the discrete element method. The simulations with different rotational speeds and drum shapes are carried out using the software EDEM. I suggest a major revision.

Comments:

(1)   The drums have a width of 8 mm. But the size of blue particles is 3 mm. Hence, only several particles exist in the direction of width. This seems unreasonable.

(2)   The rotational speed of the drum is shown in Fig. 2. But the rotational speeds such as 3.14 rad/s, 8.64 rad/s, 15.64 rad/s and 21.7 rad/s, are used in Figs. 3-5, 7-9. Where does the rotational speeds in Fig. 2 used? What is the relation between the rotational speed in Fig. 2 and those in other figures.

(3)   The rotational speed history in Fig. 2 is complicated especially after 25 s, which seems to the disadvantage of finding the particle motion behaviors and properties. Why is this rotational speed history used?

(4)   The particle sizes are 1 mm and 3 mm. Do the particle sizes conform with any distributions?

(5)   The coefficients of restitution and friction are related to two materials or structures. Hence the corresponding materials and structures should be point out clearly.

(6)   Hertz-Mindlin model have several types for discrete element interaction, such as with and without slip. What kind of Hertz-Mindlin model is used in this paper?

(7)   On Line 155, “Where” needs to be change to “where” without any space on its left.

(8)   Some figures, such as Figs. 8-11, are not clear enough. These figures need to be revised.

(9)   Clerical error, such as “rad/s2”. The reference number is not shown in correct form, and the necessary spaces and brackets are missing.

(10) Some important references are missing:

[1] Basinskas, G., Sakai, M. (2016). Numerical study of the mixing efficiency of a ribbon mixer using the discrete element method. Powder Technology, 287, 380-394.

[2] Gao, W., Liu, L., Liao, Z., Chen, S., Zang, M., & Tan, Y. (2019). Discrete element analysis of the particle mixing performance in a ribbon mixer with a double U-shaped vessel. Granular Matter, 21(1), 1-16.

(11) The authors state that “It is shown that the mixing of particles is improved at the rolling and cascading regime, and the segregation of particles can be found at the cataracting regime and centrifuging regime” in the conclusion. The mixing index is not calculated. I did not find a support for the conclusion. Please explain this clearly.

Author Response

Dear reviewers, thank you for your careful review of this manuscript. Your comments are of great significance for the revision and improvement of this manuscript, which has been carefully analysed by the author's team and refined by the manuscript. The author team has provided thoughtful responses to each of your review comments, as detailed in the word document

Author Response File: Author Response.docx

Reviewer 3 Report

The current work focuses on Numerical simulations of particle motions at continuous rotational speed change in horizontal rotating drums. Via DEM data, the motion of particles of transient characteristics is related to the variation of rotational speed, including both the velocity vector and particle velocity probability density. The number of contacts change indicates that the rolling regime exhibits the maximum number of contacts, and it decreases as the rotational speed increases.

The author’s great effort into the manuscript, but minor issues should be addressed. Extensive editing of English language and style required.

- The introduction doesn’t provide sufficient background and all relevant references are not included.

- The novelty of this work is not highlighted and the author's contribution was unclear compared to other previous works.

 -The first appearance of abbreviations should have a full definition e.g. DEM.

- Correct and make one system style for the numbering of references in the introduction.

- Correct the position of the legend of Fig.3 and Fig.4.

- All parameters in equation 1, should have full definitions in the text.

- Make one system style for references, sometimes starting with full name e.g, ref.2, and sometimes starting with abbreviation e.g. ref.1.

Author Response

Dear reviewers, thank you for your careful review of this manuscript. Your comments are of great significance for the revision and improvement of this manuscript, which has been carefully analysed by the author's team and refined by the manuscript. The author team has provided thoughtful responses to each of your review comments, as detailed in the word document

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The revised paper is much improved. Nevertheless I would like to see some additional results those I asked in ny second review.

Comments for author File: Comments.doc

Author Response

The author team has carefully read your review comments. Thank you for your careful review. Please refer to the word document for the comments.

Author Response File: Author Response.doc