Optimization of the Circular Experimental Channel for PIV Measurements of Internal Aerodynamic Cases

Round 1

Reviewer 1 Report

The paper is generally well-prepared and can be accepted after minor revision.

An actual photo of the experimental setup is to be presented.

The data acquisition system is to be presented with more details.

Figures 8 to 11 have low resolution.

It will be interesting to present the streamlines.

The paper is to be checked against misprint and grammatical mistakes.

Author Response

Dear reviewer,

I would like to start by thanking you for your helpful review.

Here are the comments on each of your points:

• The actual photo of the experimental arrangement has been added as Figure 7b.
• Information about the data acquisition system has been expanded.
• Figures 8 to 11 (in the new order 8, 9, 10, and 12) have been better arranged, and the resolution has been increased.
• Streamlines added (Figure 13).
• Multiple people and Grammarly software have been used to check misprints and grammatical mistakes.

I hope we have met your expectations.

Best regards,
Jaroslav Pulec and co-authors

Reviewer 2 Report

The authors performed an experimental work to optimize a circular experimental channel for PIV

measurements of internal aerodynamic cases.

The paper can be accepted after addressing the following comments:

1.      The title of Fig. 2 should be more precise.

2.      The English level is relatively low, it should be improved.

3.      A photograph of the experimental setup should be added.

4.      What are the uncertainties relative to the presented results.

5.      What is the interest of the BP filter?

6.      A nomenclature should be added.

7.      An introductive paragraph should be added to the section ‘’results and discussion’’

8.      More details about the pre-processing should be provided

Author Response

Dear reviewer,

I would like to start by thanking you for your helpful review.

Here are the comments on each of your points:

• The Figure 2 title has been refined.
• Other reviewers rated the level of English as "Moderate English changes required" or "English language and style are fine/minor spell check required," and it is not entirely clear what is meant by your comment. However, the manuscript has been checked by several independent people as well as grammar software. We will ask for an external corrector in the next round if it is still insufficient.
• The photo of the experimental arrangement has been added as Figure 7b.
• The uncertainty analysis has been added through Figure 14 and commentary in the text.
• The purpose of using the BP filter was commented on in more detail in Section 3.
• The nomenclature has been included at the end of the manuscript.
• The introductive paragraph in the "results and discussion" section has been added.
• More details on pre-processing have been written in Section 6.

I hope we have met your expectations.

Best regards,
Jaroslav Pulec and co-authors

Reviewer 3 Report

The manuscript presents a study on the optimization of the circular experimental channel for PIV measurements. The analysis focuses on the optimization of circular experimental setup in terms of methods and preparation, it is based on previously conducted research (why not included in the previous or future work with that setup?) made by the authors and utilizes information from the literature. It is already well known that matte black spraying it’s extremely effective to obtain better results during PIV measurements, however the investigation of different surface modifications could be interesting.

It is not clear which optimization obtained from the “optimization” claimed in the title following the results and the conclusions.

The methods are basic, and the cases analyzed are limited. The methods, data utilized and results sections sufficiently clear, the results section and the conclusions need improvement. The paper could benefit from an extension of the case studied, the calibration and a clear explanation or utilization of the “optimization” resulted from this work.

Review summary: The research is clear in most sections; the sections are sufficiently described and detailed. The paper topic is interesting, even if it is limited to a restricted audience of experts. The methods, procedures and presentation of the study and results are sufficient. Minor revision required prior the acceptance of the work.

Hereafter some points that needs to be revised:

·         Abstract: emphasize the results from the optimization performed.

·         Section 5: revise from 175 to 185, somehow trivial to understand. From row 207 to 210, are there any evidence that it does not affect the nature of the flow.

·         Section 6:

o   Improve the quality of Figures 8 and 9 (i.e. increase dpi)

o   Row 272, why it has not been performed a calibration with a finer marker grid?

·         Conclusions: please expand the conclusion section following more tests or better explain the potential optimization for further research based on the achieved results of this work.

Hereafter, some recent works that can be useful for the revision of this study in terms of similar experiments, limitations, and validations:

o   https://doi.org/10.1007/s00348-022-03529-z

o   https://doi.org/10.1080/01457632.2022.2034084

o   https://doi.org/10.1016/j.ijheatfluidflow.2022.109049

o   https://doi.org/10.1051/epjconf/202226401020

Author Response

Dear reviewer,

I would like to start by thanking you for your helpful review.

Here is a comment on each of your points:

• Optimization results were emphasized in the abstract.
• Section 5: Information in rows 175 to 185 (in the unedited manuscript) has been partially "dissolved" in the introduction in the description of reference [20]. The information about the shape of the pipe before and after the measured section is irrelevant in this section. The measurements were made under identical flow conditions; only the straight section was replaced by a modified one. This information has been added to Section 6.
• The quality of figures 8, 9, 10, and 12 has been improved.
• Row 272 (in the unedited manuscript): Information on the reason for calibration with "an insufficiently fine" target was added at the end of section 6. The reason is that the focal point of the work was the elimination of reflections, not distortion. Moreover, such a wide calibrated area is fully sufficient in terms of the requirements for the results in work related to the development of the ultrasonic flowmeter in reference [20]. Therefore, it was not necessary to perform finer calibration even in this "optimization" study.
• The conclusion was expanded to include your recommended options for future research.

I hope we have met your expectations.

Best regards,
Jaroslav Pulec and co-authors

Round 2

Reviewer 2 Report

After revision, the paper can be accepted for publication.