Effect of the Curvature Radius on Single-Droplet Dynamic Characteristics within a Concave-Wall Jet

Round 1

Reviewer 1 Report

General Comments : This paper examines the effects of curvature radius on the dynamics of a single droplet within a concave-wall jet, specifically focusing on the hydrocyclone's centrifugal force field and droplet deformation. The authors use both numerical simulation and experimental data to investigate these effects. Here are some critical, to-the-point scientific comments on the paper:

1. he paper details an experimental setup involving a water jet system, CCl4 droplets generator, and real-time image acquisition system. However, more information about the specific conditions under which the experiments were conducted (e.g., droplet size, jet velocity, temperature) would enhance the reproducibility of the study.

2. The validation of the numerical simulations with experimental data is commendable. It would be beneficial to have more details on the validation process, including any discrepancies between the simulations and experimental results and how these were addressed.

3. The study's focus on normalized interfacial energy (γ) and stretching performance is innovative. However, a more detailed analysis of how these parameters are affected by other factors, such as fluid viscosity or temperature, would be insightful.

4. The paper discusses the pressure distribution inside the droplet and its relation to the curvature radius (R0). It would be beneficial to expand on how these pressure variations impact the overall stability and breakup mechanism of the droplet, especially in different fluidic environments.

5. The study identifies three stages of droplet behavior (free-falling, spreading at the jet boundary, and breakup). It would be interesting to see a more detailed phase analysis, especially regarding the transition criteria between these stages.

6. The paper presents percentage increases in the maximum γ value with the increase of R0. A more comprehensive statistical analysis, including error margins and the significance of these changes, would strengthen the study's conclusions.

7. While the study provides theoretical insights, its practical applications, particularly in the design of liquid-liquid heterogeneous phase separation equipment, are not deeply explored. A section discussing potential industrial applications and design implications would be valuable.

English correction need 

Author Response

First of all, we are grateful to the reviewer. We can see that the reviewer has a deep theoretical study about multiphase flow, and it is our honor to obtain your review and help. The suggestions from the reviewer helped improve our study and theoretical foundation.

Thank you very much for reviewing the manuscript. The centrifugal force field was formed by rotating flow in a hydrocyclone. The trajectory of the discrete droplet was closed to the concave-wall under the action of centrifugal force and gravity. The paper expected to accurately describe the dynamic characteristics of discrete droplets in concave-wall jet to explain the mechanism of enhanced heterogeneous separation. Your suggestions were very helpful for us to improve the quality of the paper. We cherish this opportunity very much and made a serious revision to the paper according to your suggestion. It is possible that some questions were not answered very deeply and do not meet your requirements due to our inadequate level. Sincerely hope that the reviewer can give us the opportunity to make further modifications. Thanks again for your review and help.

Author Response File: Author Response.pdf

Reviewer 2 Report

-Add more literature related to jet flow and CFD. Also describe the models used by previous researchers.

-literature gap is not stated clearly.

-Add references to the governing equations.

-Discuss about the model based on which you have taken the dimension. Where is their application and what problem you are addressing related to them?

-Boundary conditions are taken on what basis?

-For meshing, convergence test is necessary. Discuss about them before choosing a mesh size.

-Figs. should be clear and big. Contours should be clearly visible.

-Plots should be bigger.

-Add convergence of your results with previous studies.

-Add some Future scope.How your studies can be extended?

Author Response

Thank you very much for taking the time to review this manuscript. We appreciate your clear and detailed feedback and hope that the explanation has fully addressed all of your concerns. 

It is possible that some questions were not answered very deeply and do not meet your requirements due to our inadequate level. Sincerely hope that the reviewer can give us the opportunity to make further modifications. Thanks again for your review and help.

Author Response File: Author Response.pdf

Reviewer 3 Report

I will not comment on the simulation setup for lack of familiarity with Ansys software.

The research in its simulational and experimental parts appears sound. The Authors show that their simulation does present results consistent with experiment, however I believe this could warrant further discussion. As the point of conducting simulations is to obtain results without the necessity of an experiment, it would be good if it was showed the simulation can well stand in for it. As it is now, Figure 4 might be slightly misleading as it is tempting to see the simulation as somehow peculiarly attuned to Droplet 3 spanwise, and then wonder why is it not the same for streamwise. Perhaps it could be remedied by presenting the experimental data as an average "path" within a range of uncertainty in which simulated data is also contained.

Pressure field distribution (Figure 9) is seemingly presented without simulated data, even if it would have been welcome, if possible.

These issues however do not constitute enough for me to demand revision.

Author Response

Thank you for the reviewers’ comments concerning our manuscript entitled “Effect of curvature radius on single droplet dynamic characteristic within concave-wall jet”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet approval.

It is possible that some questions were not answered very deeply and do not meet your requirements due to our inadequate level. Sincerely hope that the reviewer can give us the opportunity to make further modifications. Thanks again for your review and help.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

All comments are addressed 

Ok 

Reviewer 2 Report

All the revisions are ok