Numerical Study of Sediment Erosion Analysis in Francis Turbine
Round 1
Reviewer 1 Report
The reviewer wants to thank the authors for their paper and has to apologise for the delay of the review. He/she has focused on the clear version and try to see it as a new and separate submission. There are some points/suggestions, which should be addressed by the authors:
- General comment I: The reviewer is not fully convinced that sustainability is the correct journal. He/she would suggested water. But nevertheless, it would help, if the authors cite comparable paper in the journal.
- Abstract: Please add the software ANSYS-CFX in the abstract as well as in the key-words
- Line(L) 47-54: the reviewer would suggest the following additional literature references. Management of reservoir sedimentation https://doi.org/10.1016/j.ijsrc.2016.06.001and https://doi.org/10.1080/00221686.2016.1225320; negative impact of fine sediment in the reservoir causing a blockage of the intake https://doi.org/10.3390/w10081066; and massive problem with bigger objects as presented in the paper https://doi.org/10.1016/j.engfailanal.2010.09.039
- L88 variable W should be mentioned in the text
- L100, 104 112 citation not correct. Why do the authors change the style in the paper? Please check for further comparable errors.
- There are to section 2.1. This part should be reorganised and maybe the general part can be included in the introduction / general part and the CFX specific into the next section 3.
- L146: Please delete the first sentence. 3D-modelling is widely used and …
- L161: no, grid independence and convergence are something complete different. The numerical simulation can have a very good convergence, which just indicates that the error of the numerical solution is small. The grid independence test shows, that the space discretisation has no effect on the solutions, which means that the mesh is fine enough to cover the flow phenomena. Please clarify this in the text!
- L 163: porotype turbine? Explain this please.
- General comment II: The author should explain in a clear overview at the beginning which scale is used (model, nature experiment, nature big) and also a clear overview which model is switch on in which section and why also only some GV-angles / concentrations are further investigated. A clear story/path/ development is missing and makes it hard to read the paper.
- Why are there two Figure 3?
- Table 2 presents the results of which mesh No in Table 3?
- Table 2: Ok y+ min and max are mentioned but it is crucial where the max value occurs. Starting with the used models: Does those have some guidelines or best practice values for y+? Is the inflation layer hold constant for the mesh test or also change? In a next step it should be proven, that the results of the erosion model are also independent of the mesh and especially of the inflation layer.
- L206 and 220 both lines mention the pressure. This is a relative pressure, correct? Which reference pressure was used? Especially for cavitation models those is often set to 0 Pa, so that the Absolute Pressure == Pressure. But with a choice of 0 Pa at the outlet, this would lead to a full cavitation at the boundary. If the RevPres is bigger, the reviewer is concerned if the cavitation model correctly identifies the cavitation zones. Was this tested?
- Table 4: References?
- Figure 5: did the authors take those pictures themselves?
- Section 4: at the beginning of this section the author should briefly introduce the following results and the logical path through it as well as a test matrix to see which combination was applied for which model combination.
- L280: all or some other conditions? Please clarify this. Similar L325
- L290: Location (1) in Figure 6(a), at the moment it is confusing.
- General comment II: are those numerical simulations with the additional models conducted as a restart? Did the authors have to change something (timestep?) Did the convergence criterion change?
- Figure 8: the particle inflow rat is the input und the erosion rate is the result? Please change the axis. And a grid would be useful and at the moment the reviewer can only guess the correct inflow rate. Why not using 10,30,50,70 ?
- Figure 8 II: which GV angle
- Figure 12: please also present the original efficiency.
- L 372/373 and again L405: the values are not clear. Can you include this in a graph?
- Are the results of the additional models also independent of the chosen grid?
- Nomenclature is not complete. SSU, KIMM, n , \alpha, E, R .... please check it!
The reviewer sees the potential and the efforts of the research work but the presentation needs some further work. At the moment, a critical reader could argue that you just switched on some additional models and finished. Please highlight the concept and novelty of the paper. A clear guidance for the reader would make it far easier to understand it. He/she is looking forward to read the corrected version.
Author Response
Dear Professor,
Greetings.
As per your recommendations/suggestions, we tried to put point-by-point response in the revised manuscript. Could you please find herewith the enclosed point-by-point response for your ready reference.
Regards
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is my third review on this paper. The manuscript is much improved but I still check that the Authors did not apply uncertainty propagation and did not use the proper number of figures in expressing, e.g., the efficiency in Table 4. An experimental efficiency 0f 93.292% means an accuracy to the fifth digit which is by far not reliable in fluid mechanics (it is in physics of particles). In a similar way the efficiency of the simulated results cannot be accurate to the fifth digit, because the code itself is not so accurate.
I suggest to the Authors a thorough application of the criteria for error propagation, see, e.g., the methodology applied in DOI: 10.1007/s10652-014-9369-9 for complex systems, eventually with the application of a Monte Carlo method as in DOI: 10.1017/jfm.2015.405. It is not enough to write down eqs 14 and 15, there must be coherence between the output of the error propagation and the figures and the plots.
This is a major flaw: uncertainty analysis is not merely an exercise, but must control the flow chart of the data interpretation.
Author Response
Dear Professor,
Greetings.
As per your recommendation, we tried to put point-by-point response in the revised manuscript. Could you please find herewith the enclosed point-by-point response for your ready reference.
Regards
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The reviewer wants to thank the authors for their corrections. There are some points, which have to be worked on.
- Point 1: Maybe the reference to one or two paper in sustainability could help to show that it is the correct one.
- Point 7: Line old (Lo)146 new line (L) 153: Please delete the sentence: “Geometrical modeling is necessary for computer simulation; given the fact, a 3-D model of the Francis turbine model was made from the information provided. ” It is obvious that a 3D-model has to be made.
- L 110: Truscott,1972 … wrong citation. Please check the paper again!
- L 165: The sentence starting with “Because of the complex…” doesn’t make sense. It was not ideal in the first version but now it’s worse. General, grid and mesh are the whole discretization of the fluid domain. The reviewer assumes that it should be mesh elements or nodes? Please correct this complete section and previously read up a literature source for this to use the correct terminology.
- General comment II: The reviewer assumes that the authors didn’t understand the point. Please read it again and include in section 3. as 3.1 an overview, which allows the reader to understand the following steps by answering the questions. The concept of the paper has to be presented and this is a good opportunity to give the overview and explain why only some GV-angles and so on are further investigated.
- L 257: Is the caption for this figure missing? Please, also check the further captions.
- Point 12: Ok please include this in the caption.
- Point 13: please mention the changes and what was investigated. Only a reference or only a total number of elements is not enough as an answer to a question/ description in the paper.
- Point 14: When you have presented it at conferences, why is this not mentioned in the paper? Being famous doesn’t make you immune against mistakes and not getting questioned at a conference is not the same as a review. Please answer my questions and mention the reference pressure in the paper.
- Point 15: So those results are not presented previously and this is new? Is this correct? In this case, no further references are needed.
- Point 17: why didn’t the authors include such an overview.
- Point 18: No, it was not clear but now with the correction of the GV it is. Thank you for the corrections.
- Point 20: no restart ok. The reviewer is pretty sure that the ANSYS-CFX guidelines for cavitation is that you first run the model without the cavitation model until a stable condition is reached and after this the cavitation model is switched on. This is important, because a bad initial condition can cause vapour and make it hard to get a correct result.
- Point 21: Ok, which values is used for x and y is not a big thing, but it should be always clear in the caption what is the input and please check all graphs that the values of the axis are correctly set and allow to identify the run. For example, L 353 the particle inflow rate is 10,30,50,70, and the axis shows the values 20,40,60,80,100
- Is the efficiency in the Figure in Line 412 the same as in Line 415?
- Please delete the old figures completely. It is better just to mention in the response which are changed and it makes it less confusing.
The reviewer thanks the authors for their corrections and is looking forward to the corrected version of the paper.
Author Response
Dear Professor,
Greetings and good morning.
As per your recommendation/suggestion, the point-by-point response of the manuscript (Sustainability-441254) the enclosed herewith for your ready reference.
We tried our best to revise the manuscript.
Regards
Md Rakibuzzaman
Author Response File: Author Response.pdf
Reviewer 2 Report
I have now received the revised manuscript. Some improvements have been implemented, but the motivations of the authors to justify the absence of uncertainty analysis (two equations without application in data analysis are not enough) lack reliability.
Author Response
Dear Professor,
Greetings and good morning.
As per your recommendation/suggestion, the point-by-point response of the manuscript (Sustainability-441254) the enclosed herewith for your ready reference. We inserted the limitation of uncertainty in the manuscript.
We hope, your kind understanding will be highly appreciated in this regards.
Yours Sincerely,
Author Response File: Author Response.pdf
Round 3
Reviewer 1 Report
The reviewer wants to thank the authors for their corrections. Please provide a complete clear version of your paper (without the corrections marked – this can also be uploaded as a supplementary file) and check the following points:
- The captions of each figure should allow to understand the figure without reading the full text. In the current version some are green marked and it is not clear if they are deleted or changed. Please provide a clean version as well.
- Fig 3 Page 9: the vertical dotted line marks the used grid?
- Also check the Fig. 13 and 14. The reviewer assumes that the second should be a difference change?
- Yes, you did it like this and talked with Prof Satoshi Watanabe about this 5 days ago. And did he tell you to run from an initial condition without a restart with the cavitation model and use a reference pressure of 1 atm instead of the 0 atm, as used in the examples of CFX? The first one can lead to cavitation where nothing occurs based on a bad initial condition and the second one lead to the fact that the Absolute Pressure is not equal the Pressure which is calculated by the solver (Absolute Pressure = Reference Pressure + Pressure). CFX is a very reliable solver and the reviewer assumes that it automatically uses the Absolute Pressure but he/she is not sure. This has to be checked and at least be correctly explained in the text.
The reviewer is looking forward to the corrected version.
Author Response
Dear Professor,
Thanks and good evening.
The enclosed file is herewith provided the point-by-point responses for your ready reference.
We inserted captions of all figures. Also, we revised the manuscript to complete a clear version as per your recommendation.
Yours Sincerely
Author Response File: Author Response.pdf
Round 4
Reviewer 1 Report
The reviewer wants to thank the authors for their corrections. The quality of the paper has significantly increased. Please correct two points> (a) please chose a narrower y-axis limitation for Fig. 3 maybe [85,95] and (b) Fig 14 difference to what? – please clarify this in the caption. Thank you.
Author Response
Dear Professor,
Thanks a lot.
As per your suggestions, we revised Figure 3, and the caption is included in Figure 14. The enclosed file is herewith for your ready reference.
Yours Sincerely
Author Response File: Author Response.pdf
