Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Please refer to the attached document.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Manuscript Number: water-3932649
Title: Internal flow characteristics and modal analysis of an ultra-low 2specific speed pump as turbine3
The work presents a study on the evaluation of internal flow characteristics of PAT for its design optimization and stable operation.
The paper presents a comprehensive literature review, and the fundamentals for model understanding are well established.
Some fundamental points could be reviewed:
1)
Fig. 10 and Fig. 11 show different behavior.  Would the authors explain these results?
2)
In view of the primary objective of the paper, that is, providing theoretical guidance for its design optimization and stable operation, could the authors offer design criteria using entropy generation and the DMD technique?
3)
Considering that PAT, at the present moment, are not designed, this concerns the pump design.  How is the direction for the use of the presented methodology?
Some points could be reviewed to increase the paper quality:
1)
The term USSPAT is used in the article without a definition.  When it appears for the first time, it should be defined.
2)
Please provide the physical units for the variable n, Q, and H in Eq. (30).
3)
Please provide the experimental uncertainties in Fig. 6.
4)
Please provide a figure with the clear position of the pressure sensor employed to measure pressure pulsations.
To format considerations:
1)
Position Fig. 1 appropriately in the available space.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This paper combines CFD and experimental approaches to study the internal flow characteristics and modal analysis of an ultra-low specific speed pump as a turbine. The originality of the paper is clear, the technical approach is well-defined, and the research methods are reasonable. Overall, the quality is good; however, some details could be further improved. I recommend minor revisions for acceptance. Specific suggestions are as follows:

(1)In the abstract (lines 20-25), it is recommended to add clearly quantifiable conclusions based on these research results.

(2)Some keywords are not very appropriate, such as "ultra-low specific speed pump as turbine"—the phrase is too long and may hinder retrieval. "Numerical simulation" is too broad and needs further refinement.

(3)At line 124, although the main innovation point is identified, the current research value should be further clarified.

(4)Abbreviations like USSPAT should be spelled out fully when first introduced in the text. Although abbreviations are provided later, this section requires a comprehensive check throughout the manuscript.

(5)The last paragraph of Chapter 1 should include an introduction to the overall structure of the paper.

(6)Chapter 2 should include an expanded introduction to relevant fluid mechanics theories such as the Navier-Stokes (N-S) equations. The section 2.1 on the SST turbulence model could be condensed.

(7)Section 3.2 needs to provide detailed grid parameters, especially clearly describing Y+ values at the walls.

(8)Section 3.3 should include a figure showing the overall computational model, with boundaries in each region clearly labeled.

(9)Section 3.4 should incorporate an error analysis of the experimental results.

(10)Some Equations in section 4.1 would be better placed in Chapter 2 as foundational explanations supporting the paper; they should not be in this section unless they are part of your original contribution.

(11)For Figure 19 (cloud diagram), the variables depicted need to be clearly specified. Additionally, some figures in the text lack units.

(12)It is recommended to add clearly quantifiable results in the conclusions.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf