Experimental & Computational Fluid Dynamics Study of the Suitability of Different Solid Feed Pellets for Aquaculture Systems
, Karel Petera 2,†, Petr Císař 1, Vlastimil Stejskal 3 and Mohammadmehdi Saberioon 1,4,*Round 1
Reviewer 1 Report
In general, I think it is worthy of publishing. Some points should be included in the manuscript in order to improve the publication.
- The presentation of the literature could be improved. The authors analyze a lot of papers. A better classification and a comparative analysis between them would be useful.
- The authors should describe in more detail the experimental setup and the experimental procedure.
- The discussion section is relatively weak in the present form and should be strengthened with more details and justifications.
- In the conclusion section, the authors summarize the main points of their study. The authors should explain the contribution of their results in comparison to the results of other researchers.
Author Response
Dear Reviewer 1,
We highly appreciate your thorough review of our manuscript. The authors have modified the manuscript accordingly. The authors also answered the reviewer's comments as below :
In general, I think it is worthy of publishing. Some points should be included in the manuscript in order to improve the publication.
(1) The presentation of the literature could be improved. The authors analyze a lot of papers. A better classification and a comparative analysis between them would be useful.
Answer: As the reviewer recommended, the authors improved the introduction and added the comparative analysis of the literature.
(2) The authors should describe in more detail the experimental setup and the experimental procedure.
Answer: At the end of section 2.3, more details about measuring the settling velocity were added, including accuracy estimation.
(3) The discussion section is relatively weak in the present form and should be strengthened with more details and justifications.
Answer: The discussion has improved in the revised version of the manuscript.
(4) In the conclusion section, the authors summarize the main points of their study. The authors should explain the contribution of their results in comparison to the results of other researchers.
Answer: As mentioned in the conclusion, this manuscript is the first study dealing with identifying the pellets' properties and correct settings of the model in CFD solvers. Therefore, authors cannot perform any comparison between results from this study and previous research in literature.
Reviewer 2 Report
Authors presented analysis on the motion of solid feed pellets in a fish tank. Experimental data and CFD analysis using ANSYS Fluent software were used. The effective density of feed pellets in water was determined. Paper gives interesting results; however, some sections must be improved. Below comments to improve the manuscript:
Bring some quantitative results and the main finding into the abstract. Numbers are required for better understanding of the work.
Please provide scientific novelty of your paper in the end of Introduction.
The originality shall be justified by highlighting that the manuscript contains sufficient contributions to the new body of knowledge.
In the Introduction section, the authors need to clearly state what knowledge gap their work will fill compared to the literature review. Complete the introduction.
Have you carried out uncertainty analysis?
The accuracy of the measuring equipment must be provided.
CFD model validation must be presented.
Deeper explanation and discussion must be given for results analysis.
Revise Conclusions: quantitative results must be also presented.
Author Response
Dear Reviewer 2,
Thank you for a thorough review of our manuscript. Following your comments, we have made revisions to all identified areas. The authors answer to your comments also listed as below :
Authors presented analysis on the motion of solid feed pellets in a fish tank. Experimental data and CFD analysis using ANSYS Fluent software were used. The effective density of feed pellets in water was determined. Paper gives interesting results; however, some sections must be improved. Below comments to improve the manuscript:
(1) Bring some quantitative results and the main finding into the abstract. Numbers are required for better understanding of the work.
Answer: The authors added some quantitative results into the abstract, illustrating how pellets' residence time differs with the injection position at the liquid surface and the maximum difference between the studied two types of pallets.
We put some quantitative results into the abstract, illustrating how the residence time of pellets differs with the position of the injection at the liquid surface, and what is the maximum difference between the studied two types of pellets.
(2) Please provide scientific novelty of your paper in the end of Introduction.
Answer: The description of the scientific novelty of our study has been improved (see the end of section 1. Introduction).
(3) The originality shall be justified by highlighting that the manuscript contains sufficient contributions to the new body of knowledge.
Answer: The authors added the following sentences in both Introduction and Conclusion in order to highlight that the manuscript contains sufficient contributions to the new body of knowledge.
(4) In the Introduction section, the authors need to clearly state what knowledge gap their work will fill compared to the literature review. Complete the Introduction.
Answer: The knowledge gap highlighted in the Introduction.
(5) Have you carried out uncertainty analysis?
Answer: Concerning CFD accuracy, the grid convergency index was evaluated as 11.6% for the mesh size 420 000 used in our simulations (based on average velocities in three horizontal planes). Concerning uncertainty analysis, when measuring the settling velocity of particles cannot be done as the feed pellets cannot be used repeatedly.
(6) The accuracy of the measuring equipment must be provided.
Answer: The only measurement equipment used in the study was the digital camera used for pellets diameter and settling time measurement.
The accuracy of the measurement of the diameter of the pellet is given by camera resolution and by the distance between the camera and the pellets. We added the text describing the accuracy in subsection 2.1.
The settling time was determined from the recorded movie with accuracy limited to one frame. The accuracy of the camera from the point of view of the diameter measurement can be calculated from the camera chip resolution and distance from the surface.
We added to the text an estimation of the accuracy concerning the settling velocity measurement (see the end of subsection 2.3).
(7) CFD model validation must be presented.
Answer : Figure-6 was added to the manuscript illustrating a comparison of simulation data (velocities) with experimental data [Hanak, 2016]. In total, differences in 24 points in the tank were evaluated, the average difference between the experimental and simulation data in all these points is 11%.
Concerning the validation of particle tracking, this is planned for our future work.
(8) Deeper explanation and discussion must be given for results analysis.
Answer : Discussion has improved
(9) Revise Conclusions: quantitative results must be also presented.
Answer : The conclusion has been improved, and as the reviewer recommended, quantitative results added
Reviewer 3 Report
The authors carried out physical experiment and CFD study of the trajectory of solid fish pellets in a cylinder. Both the experiment and the CFD study were well designed and presented. I do, however, have the following comments:
- The biggest assumption in the CFD study is that the pellets are completely passive and its existence does not affect the flow structure. I am aware that the authors have stated the limitation of this assumption. However, I would like to see a little bit more discussion of the effect of pellets, e.g., the effect of their settling on the turbulence structure, their agglomerates, etc., if they are not modeled as completely passive.
- Please provide a reference to Eqn. (5).
- Please explicitly specify if it is a 2D or 3D model. Looks like it's 3D. Please also show a 3D domain and mesh. How long did the simulation run? What are the grid sizes? How big is the time step? These information need to be presented explicitly.
- Line 119: 0.8 m2/s and 0.08 m2/s are flow rates, not velocities. Please correct.
- Figure 9: What is the definition of "position angle"? Please clarify.
Author Response
Dear Reviewer 3,
Thank you for a thorough review of our manuscript. Following your comments, we have made revisions to all identified areas. The authors answer to your comments also listed as below :
The authors carried out physical experiment and CFD study of the trajectory of solid fish pellets in a cylinder. Both the experiment and the CFD study were well designed and presented. I do, however, have the following comments:
(1) The biggest assumption in the CFD study is that the pellets are completely passive and its existence does not affect the flow structure. I am aware that the authors have stated the limitation of this assumption. However, I would like to see a little bit more discussion of the effect of pellets, e.g., the effect of their settling on the turbulence structure, their agglomerates, etc., if they are not modeled as completely passive.
Answer: The pellets are modeled as passive because of the nature of the fish feeding process. The amount of pellets used for the fish feeding in the RAS is insignificant from the point of view of the turbulence structure. The feeding is usually done several times per day with a small number of pellets. Therefore the effect of pellets settling to the flow field is very low. It was added to the discussion part.
(2) Please provide a reference to Eqn. (5).
Answer: Paul, E.L., Atiemo-Obeng, V.A., Kresta, S.M.: Handbook of Industrial Mixing, John Wiley \& Sons: New Jersey, 2004. added.
(3) Please explicitly specify if it is a 2D or 3D model. Looks like it’s 3D. Please also show a 3D domain and mesh. How long did the simulation run? What are the grid sizes? How big is the time step? This information need to be presented explicitly.
Answer: It is 3-D model which we added explicitly in the revised version of the manuscript and in the caption of Figure 5, where we also replaced the 2-D cross-section of the mesh by 3-D view to make it more clear. The authors also added the time of simulation to get the developed velocity field (70 minutes). The number of mesh elements (420 thousand) was already mentioned in the text, but it was also added to the caption of Figure 5. Because we have chosen the one-way coupling between the particles and fluid phase, the flow field was obtained in a steady-state simulation, and particle tracking was part of the postprocessing procedure where no time step needs to be specified.
(4) Line 119: 0.8 m2/s and 0.08 m2/s are flow rates, not velocities. Please correct.
Answer: As the reviewer mentioned, Units were miswritten; they should be m/s, therefore velocities (not flow rates), is corrected in the revised version.
(5) Figure 9: What is the definition of “position angle”? Please clarify.
Answer: As depicted in Figure 10 on the left, the position angle and reference to it were added to the Figure 9 caption.
Round 2
Reviewer 2 Report
Authors made needed revisions and improved manuscript according reviewers' comments.
