Experimental and OLGA Modeling Investigation for Slugging in Underwater Compressed Gas Energy Storage Systems

Round 1

Reviewer 1 Report

In this paper, compressed gas energy storage (UW-CGES) is an interesting topic for different applications. And when the author added the simulation studies for validation of the results of its experiments, they made this manuscript valuable for publication in this journal and its writing in good language. However, before publication, I suggest the authors answer these questions.

1-      In the abstract section, the authors need to add the main outcomes as a number, percentages…. etc.

2-      In the abstract section, what is mean OLGA model? I suggest writing the full name.

3-      For me as a reader, it's unclear how to store the energy! Kindly, could the author explain this methodology in simple words?

4-      Is it possible to make a graphical abstract to show the ideas and how they connect together, to clarify the steps of this work?

5-      Figure#1 in page#2, the words are not clear.

6-      In the introduction section, the author needs to show their work's novelty since there are a number of studies that have been done on the same title.

7-      The author used OLGA software to simulate their experiments while the CFD can do so and more!

8-      Figure#4 in the Z column is an inclined zero or symbol? Clarify

9-      Figures #5, and 27, the labels and numbers are not clear.

10-  Can we use non-distractive techniques such as Non-Invasive Gamma-Ray Techniques for diagnosing the flow movements and slugging in the pipes?

 Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The below suggestions will enhance the study's overall quality and provide a clearer understanding of slug flow formation in pipelines and its sensitivity to pressure fluctuations.

Ø  Incorporate specific quantitative results and key findings to highlight the research's significance and impact.

Ø  Expand the review to encompass a wider range of relevant studies and provide a deeper critical analysis of existing literature on slug flow formation and its sensitivity to pressure fluctuations.

Ø  Provide detailed information about the experimental setup and OLGA simulation, including instrument calibration and data analysis methodology. Justify parameter choices based on real-world scenarios.

Ø  Conduct a thorough statistical analysis of experimental and simulation data to strengthen validity. Interpret results comprehensively and discuss broader implications.

Ø  Address potential limitations and their impact on validity. Acknowledge sources of error and suggest future research areas to fill gaps in knowledge and improve techniques.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

This article demonstrated an investigation into the phenomenon of slugging in underwater compressed ga senergy storage (UW-CGES) systems. The authors conducted experiemtns and OLGA simulations to study the formation process of slug flow in pipelines. The study identified three distinct stages of slug flow: grwoth, ejection, and backflow. The results demonstrated a high level of consistency between experimental and simulation data, providing insights into the relationship betwen pressure and slug flow formation. The finding contribute to the understanding of UW-CGES pipelines' operational status and support safe operation. 

(1) However, the methodology of simulation, including the OLGA simulation, has the limitations of the study. Authors also did not compare with previous work and performe statistical analysis. 

(2) The paper identifies three stage of slug flow byt doe not provide a comprehesive description or visual representation. Due to the lack of detail, it will be unclear about the dynamics involved in each stage. 

Moderate editing of English language required

Author Response

Please refer to the attachment

Author Response File: Author Response.pdf