A Review on the Some Issues of Multiphase Flow with Self-Driven Particles
Round 1
Reviewer 1 Report
The manuscript presented a review on some issues of multiphase flow with self- 2 driven particles. The topic can be matched with the journal scope and the manuscript is well-written. The conclusions and propositions are appropriately organized. However,
-English should be enhanced throughout the manuscript to eliminate grammatical errors and misprints. For example, the second sentence of the abstract is too long, and many other errors can be found.
-Moreover, as the manuscript is a review paper, from a technical point of view, authors should consider new references as well. However, in the reference list, the references related to 2020 are fewer, and there cannot be seen any reference for 2021.
-The type of manuscript mentioned before the title shall be changed into “Review”. This is not an "Article".
Author Response
See Attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Manuscript Ref: applsci-1261583
Review Report
Article title: A Review on the some issues of multiphase flow with self- driven particles
In this article, a review on some issues of multiphase flow with self-driven particles is given. The paper is well presented. The authors are made this manuscript selected for good work and I find a lot of interesting information included here. Following revisions are suggested:
- More relevant literature may be added to strengthen and similar work in the Introduction section.
- In the abstract but also in the manuscript, the word “squirmer” is repeated too many times in the same sentence or on the same phrase.
- Line 250-252 “For example, 250 Bacillus subtilis forms polar clusters [55]. Bacteroides dendritic moves along the narrow, 251 long and high density zone [56]. Tubulin-dynamin forms vortex arrays [57]. Escherichia 252 coli forms long range array [58] (as shown in Figure 12).” I recommend to the authors to make a single sentence from all these sentences.
- In general, there are some grammatical mistakes, which should be carefully corrected.
Author Response
See Attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
Review on the paper "A Review on the some issues of multiphase flow with self-driven particles" by Liu and Lin
This article review on some issues of self-driven particles in fluids.
Four topics were summarized (1) interactions between self-driven/passive particles (2) aggregation of squirmers (3) the viscoelastic effects (4) axisymmetric squirmers
Although the topic sounds interesting, the article fails to give any insights mainly due to unclear writing and lack of clarifications of important underlying basic physics.
Each section enlists some examples and topics but fails to give any insights.
In my opinion, it should be substantially re-written for significant improvement (not simply major revision). Therefore, my decision is rejection.
The below summarizes some of the suggestion points which the authors must consider in re-writing.
(1) All the figures need more description and proper copy right declaration.
(2) Section 1 needs more citations in each example mentioned.
(3) Section 1 must be re-written more clearly that the suggested topics should be aligned with the four topics in later sections sections.
(4) Is the examples in section 2 related to the condition where the fluctuation-dissipation theorem is not satisfied? If so, why and how?
(5) what is hydrodynamic efficiency? The term needs to be clarified.
(6) In Section 4, the definition of Deborah number is different from conventional definition. The definition or physical meaning in the specific situation must be clarified.
(7) In section 6, for example of (3), basically, the paragraph just enlists all the rheological properties, which is unnecessary. It is suggested to propose a fewer number of important properties and describe why.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
The authors review some issues of multiphase flow with self-driven particles. This review could be timely and useful to the community if the following comments are well addressed.
- The reason why the authors are interested in these 4 issues for reviewing the recent studies of multiphase flows with self-driven particles is unclear to me. In addition, it is also not clear why the authors emphasize multiphase flow in the title and introduction parts. However, most studies they review are in the single fluid phase.
- Could the authors provide more comments on the main challenge and limitations of current investigations on hydrodynamics on active matters? What could be the future directions?
- Scientists have put increasing effort into computational studies on hydrodynamic interactions of active matters. Could the authors shed light on the computational efforts on each issue?
- The figure captions in this review could be more informative by including some details on the main findings. Some figures seem low quality to me. For example, Figure 11d still has its original markers.
Author Response
see attachment.
Author Response File: 
Author Response.docx
Round 2
Reviewer 3 Report
A second review on “A Review on the some issues of multiphase flow with self- driven particles” by Liu and Lin.
Although the authors modified some parts of this manuscript based on my comments, the overall quality is still not in the level enough for publication. Review papers should give summarizes existing and previous works on a topic to explain the current state of understanding of the topic or give any insights on the topic. The paper simply lists some related works and gives vague explanation. Let me give comments on Introduction only.
Introduction should clarify: what is "self-driven particle" by explaining its general mechanism.
“internal force together with some influence of fluid and external force” is very vague. More details should be given. There must be many different mechanisms. However, there should be a way to generalize/classify those mechanisms.
Lne19-24: Sentences in this paragraph sound awkward. I can see that the authors would like to bring an attention of self-driven particle by comparing to passive particles but it should be improved. There are different types of multiphase flows such as bubble flows. As I mentioned above, concepts of passive and self-driven particles must be clarified.
Line25-35: In terms of the definition/generalization/classification of self-driven particle, what types of mechanism (what are external forces and what are interactions to cause particle motion?) do those natural self-driven particles have must be explained. Additionally, reference for Figure1c is missing. Copyright permission must be given, which is a fundamental thing you should observe when you write a review paper. It is recommended to see other review papers.
Line 36-42: References for Figure2abs as well as copy right permission must be provided. This paragraph must be re-written in a similar way as I suggested for the previous paragraph.
Line 46-62: This paragraph is trying to classify some features of self-driven particles but the classification is vague.
Line 48-50: Grammatically incorrect. Your writing reads as Brownian motion cannot satisfy fluctuation-dissipation theorem, which is incorrect. Theoretically, passive-particle flow is also in non-equilibrium state.
Line 50-53: This needs more clarification of why that interaction causes non-equilibrium.
Line 54-56: Not even a sentence.
Line 56-57: Of course, there are various forces. However, those forces also drive passive particles. Classify those forces in terms of self-driven mechanisms. Otherwise, this enlistment is meaningless.
Line 57-61: Are any of those abnormalities related to the non-equilibrium nature in Line 50-53? Or to the force types in Line 56-57? If so, these abnormalities cannot be classified as the third feature. Otherwise, it should be classified in a different way.
Line 61-62: Is it related to the non-equilibrium nature in Line 50-53?
Line 63-85 explains the importance of the studies on self-driven particles and aspects of related researches. However, the classification is poor. Additionally, citations for each example must be given.
The context of Line 64-67 and the examples listed in Line 67-69 do not match. It is unclear how the hydrodynamic interaction is related to the natural selection.
The context of Line 70-75 (nature-inspired design) and the Line75-78 (application in some other areas) do not match.
Line 86-92 suddenly came out of nowhere. It seems like explaining some mechanisms of natural self-driven particle. It can be explained in Line 25-35 or overall arrangement should be improved.
Line 93-104 is not enough justification of the structure of this manuscript (why those four topics were chosen and organized in that way).
Author Response
This is just a review paper. Different people can review it from different perspectives.
Reviewer 3 requires that every term should be explained, e.g. "what is "self-driven particle", just like popular science books. In fact, papers are for professionals.
Reviewer 4 Report
The authors have properly addressed my comments. However, they do need to pay attention to the tone in the response letter in the future.
