Eulerian–Eulerian Modeling of Multiphase Flow in Horizontal Annuli: Current Limitations and Challenges
Round 1
Reviewer 1 Report
This article is a review one. Review articles need to be easy to understand even for non-experts. The following comments are written from this view point.
- In scientific and technical papers, equations are written in Italic style, not Roman style. In this paper, most of equations are written in Roman. Furthermore, many equations are written in the bold font and some in the fine font. The same font as the text written in fine font should be used for equations.
- According to Line 376 – 378, both terms SMa and Ma contain the drag force. Why is the effect of drag force is considered apart ? In this connection, the concrete forms of SMa and Ma should be given.
- Eq.(6): The expression of the numerator “fraction of “ is strange. Some word should be after the preposition “of”.
- Line 457: The word ”collision efficiency” appears suddenly after “collision frequency”. What is the collision efficiency ?
- Line 458: uci is defined as “critical eddy velocity”. What is the “critical” eddy velocity ?
- Line 467: V is defined as particle size (volume). Another symbol d is used for particle size in this paper. Usually the symbol V is used for volume. What does the word “(volume)” mean ? Is it “diameter equivalent to a sphere of the same volume” ? It causes confusion to attach “(volume)” to V. The reviewer suggests that the symbol d with subscript v, that is “dv”, should be used instead of V.
- Eq.(11): This expression is very simple when considering the complexity of collision frequency with the random nature of the eddies motion. How is this equation derived ? Assumptions must have been used. What assumptions have been used to derive the equation?
- Line 481 – 485: The three steps are explained in words. In addition to the words, it is better to attach a figure that illustrates these steps.
- Line 580: It is advisable to attach a figure that illustrates Sij (collision cross-sectional area).
- Eq.(15): The reference related to this equation is Rotta[93]. The reference [93] is a book dealing with single phase turbulence, not multiphase flow. It is strange that the equation deduced from single phase turbulence analysis contains bubble size.
- Eq.(16): What is Q ? Subscript 1 and 2 are supposed to correspond to location, but they need to be explained.
- Line 520: Ul is explained to be the liquid circulation velocity. The present reviewer is not familiar the expression “circulation velocity” Is it local velocity? If the word “circulation velocity” is common in the field of multiphase flow, the reviewer withdraws this comments.
- The title of Section 6 is “Limitations and ……”, but this section is actually concluding remarks. It is better to change the section title to “Concluding remarks”. At the beginning of this section or after the first sentence, put a sentence like “In this section, limitations and challenges in the study of annular flow are listed.” This sentence is an example. The authors should consider more suitable sentence.
Careless mistakes are found. Examples are shown below.
- Ref.[79]: The name of the 2nd author is Hibiki, but this name is spelled Habiki (Line 392, 394,399) in the text. Which is correct?
- Ref.[93]: Misspelling is found in the title of the book. Turbulenre -> Turbulente. This book is written in German. Thus, It is better to put a word such as “(German)” at the end of reference description.
- Ref.[97]: As above, it is better to put the word “(in Japanese)” at the end of reference [97].
- If there are references written in a language different from English, the original language with bracket should be put as in the case of Ref.[79] and [97].
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The current study reviews the existing models developed to predict two-phase flow in annuli flow. The authors analyzed various empirical correlations and numerical models of two-phase flow through pipelines. They also compared the model predictions with the experimental data and finally discussed the limitations in the current numerical models.
In my view, the paper is very well-written and makes a significant contribution to multiphase flow prediction in annuli with extensive applications in the oil and gas industry.
With appropriate consideration to the suggested comments, as well as other reviewers' comments, I find this paper appropriate for publication in the Processes journal.
Here are some minor comments:
- 1: I would recommend adding an explanation in the caption of the figure on what U_SL and U_SG stand for.
- Some equations in the text are inserted as a low-quality text. Such as Eqs. 11-13. I would recommend improving the quality of the text throughout the manuscript.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Please see attached file
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript has been properly improved.
