Performance Investigation of the Immersed Depth Effects on a Water Wheel Using Experimental and Numerical Analyses
Round 1
Reviewer 1 Report
The paper describes experiments and CFD simulations on a water wheel.
It is interesting and it may have potentiality, although a major review is suggested.
1) I think that the Authors neglected the importance of some of their interesting results, simply showing few figures, while, if they would have been more commented, they would be extremely useful from a scientific point of view. For example, Fig.12 shows an aspect very important, quite neglected by the Authors. While the immersed ratio increases, the stream water wheel gradually becomes an hydrostatic pressure machine HPM. In the stream type, the kinetic energy is mainly used, and only a little of potential energy (Fig.12a), while in the HPM (Fig.12d) the kinetic energy upstream is very low, and the head difference (i.e. the potential energy, or the hydrostatic pressure) is used to drive the wheel. Therefore, in the latter case, Eq.2 loses its meaning, because the kinetic energy is very low and negligible with respect to the potential energy, that means that at the denominator of eq.2 there should be 9810*Q*H, where H is the head difference and Q the flow rate. Therefore, in order to have a coefficient that is valid in both situations, I suggest to use the Bernoulli theorem at the denominator of eq.2. This transition is scientifically important, but neglected by the Authors. It is the very novelty of the paper, and, if not discussed and generalized, the paper has not any novelty and would not be a scientific paper. See the following review paper that discusses this aspect ""Stream water wheels as renewable energy supply in flowing water: Theoretical considerations, performance assessment and design recommendations".
2) In "Stream water wheels as renewable energy supply in flowing water: Theoretical considerations, performance assessment and design recommendations", it was highlighted that there are some open gaps in the scientific literature on this kind of wheels. In which gap does this research fit in? I think that the gap that the Authors have to cover (in addition to point 1)), is the optimal efficiency and number of blades at different blockage (or immersion) ratios, aspect that is well explained in the suggested reference and that should be considered, otherwise the novelty and importance of the paper would not be clear.
Points 1 and 2 are the two open gaps that the authors partially investigated, but mostly neglected. The paper can not be accepted as scientific paper without analyzing these topics, that are the very important gaps, and that the authors partially discussed.
3) English: I started to correct the English, but when I found several errors, I decided to stop. I suggest the manuscript to be reviewed by an English expert or by the MDPI language service. Some sentences (see for example the abstract) are very long and unclear. Please, revise the English.
4) Undershot instead of undershoot, overshot instead of overshoot.
5) If there are not head differences, the wheel is not an undershot type, but a stream water wheel. See the previous reference.
6) line 40: this is an example of sentence with bad English "because of its advantages with clean、renewable and abundant"
7) line 54: why? Overshot wheels do not need a curved shroud below them, like undershot and breastshot, thus they are apparently simpler....
8) line 57: why "alternative"?
9) Line 60: the undershot wheel uses mainly the potential energy. It is the stream water wheel that uses the kinetic energy, see ref.15, and it can become an HPM at high blockage ratios.
10) line 73: in ref.17, the optimal number of blades was 48, not 16, and a general equation was identified to generalize the results
11) line 82: he did not test the Zuppinger type, but a stream wheel with blades similar to the Zuppinger type
12) Line 84: like in ref.15, where the Sagebien wheel (straight blades) performed better than the Zuppinger type
13) Line 93: these results have been confirmed in Experimental Analysis of Effect of Canal Geometry and Water Levels on Rotary Hydrostatic Pressure Machine
14) line 107: the k-omega model was also confirmed and used in ref.17
15) lines 128-134: example of very long and confusing sentence. Furthermore, it is a stream water wheel, because there is not a drop in the channel bed.
16) line 153: add the mesh dimensions in mm and boundary layer mesh
17) Chapter 3: the error on the efficiency/power measurement should be estimated also
18) line 231: "experimented considering natural environment" not clear
19) why straight blades were used? As it can be seen in Fig.5, downstream water is uplift and a power loss is generated. Diagonal blades should be used, like in the hydrostatic pressure machine HPM. Add comments on this aspect.
20) Fig.5: it is not clear if the upstream and downstream water levels are different, like in the HPM, or if are the same, like in stream water wheels.
21) Angle instead of angel
23) As the immersion increases, the blockage ratio increases and the upstream level increases, transforming the stream water wheel into an hydrostatic pressure machine. In the hydrostatic pressure machine, the wheel rotates not due to the kinetic energy, that is very small due to the high upstream water level, but due to the hydrostatic pressure related to the upstream-downstream head difference. This aspect should be better investigated, that is scientifically important, representing a transition between two kinds of wheels.
24) Practical suggestions for the design should be drawn, and results compared with literature. Results should be generalized, as in the suggested reference, finding trends and similarity with other researches.
25) Nomenclature: add units
Author Response
Response to Reviewer 1 Comments
Thank you for your comments concerning our manuscript entitled “Performance investigation of the immersed depth effects on water wheel using experimental and numerical analyses” (Manuscript Number: Water-733907). Those comments are all valuable and very helpful for revising and improving the paper to a better scientific level, as well as the important guiding significance to our researches. The authors have studied comments carefully and would like to make suitable revisions for the present manuscript.
The main responds to the reviewers’ comments are as follows, please note that all revisions are highlighted using the "Track Changes" function in Microsoft Word and some revisions are highlighted with yellow color.
Point 1: I think that the Authors neglected the importance of some of their interesting results, simply showing few figures, while, if they would have been more commented, they would be extremely useful from a scientific point of view. For example, Fig.12 shows an aspect very important, quite neglected by the Authors. While the immersed ratio increases, the stream water wheel gradually becomes an hydrostatic pressure machine HPM. In the stream type, the kinetic energy is mainly used, and only a little of potential energy (Fig.12a), while in the HPM (Fig.12d) the kinetic energy upstream is very low, and the head difference (i.e. the potential energy, or the hydrostatic pressure) is used to drive the wheel. Therefore, in the latter case, Eq.2 loses its meaning, because the kinetic energy is very low and negligible with respect to the potential energy, that means that at the denominator of eq.2 there should be 9810*Q*H, where H is the head difference and Q the flow rate. Therefore, in order to have a coefficient that is valid in both situations, I suggest to use the Bernoulli theorem at the denominator of eq.2. This transition is scientifically important, but neglected by the Authors. It is the very novelty of the paper, and, if not discussed and generalized, the paper has not any novelty and would not be a scientific paper. See the following review paper that discusses this aspect ""Stream water wheels as renewable energy supply in flowing water: Theoretical considerations, performance assessment and design recommendations".
Response 1: The authors are very grateful for reviewer’s suggestions. The water wheel is gradually similar to a HPM as increase of immersed depth, the transition is really scientifically important and need to be researched in the near future. There is no shroud below the wheel to reduce bottom leakages for this wheel in this manuscript, in the latter case, the water level increases main because of the growth of the immersed depth, also kinetic energy is very low and potential energy is seen as the main part, however, they are all converted from the kinetic energy at the inlet, so the eq.2 still conform to Bernoulli theorem. "Stream water wheels as renewable energy supply in flowing water: Theoretical considerations, performance assessment and design recommendations", this paper has significant significance and present the guidelines for stream water wheel, we have cited it now.
Point 2: In "Stream water wheels as renewable energy supply in flowing water: Theoretical considerations, performance assessment and design recommendations", it was highlighted that there are some open gaps in the scientific literature on this kind of wheels. In which gap does this research fit in? I think that the gap that the Authors have to cover (in addition to point 1)), is the optimal efficiency and number of blades at different blockage (or immersion) ratios, aspect that is well explained in the suggested reference and that should be considered, otherwise the novelty and importance of the paper would not be clear.
Response 2: The authors are very grateful for reviewer’s suggestions. In line 108-110, we have added that "So this paper is concentrated on studying different immersed depths effect on water wheel’s performance and flow characteristics through numerical simulations. This research conducted the experiments at immersed depth of 0.8m based on a real-size model. ", It is covered as Blockage Effect in "Stream water wheels as renewable energy supply in flowing water: Theoretical considerations, performance assessment and design recommendations". Also, the guidelines were presented in this paper, we have cited it now in line 88 as ref.37.
Point 3: English: I started to correct the English, but when I found several errors, I decided to stop. I suggest the manuscript to be reviewed by an English expert or by the MDPI language service. Some sentences (see for example the abstract) are very long and unclear. Please, revise the English.
Response 3: The authors are very sorry for our negligence. We have corrected irrelevant details in abstract. Also we have edited the manuscript extensively. All revisions are highlighted using the "Track Changes" function in Microsoft Word and and some revisions are highlighted with yellow color.
Point 4: Undershot instead of undershoot, overshot instead of overshoot.
Response 4: The authors are very sorry for our negligence. We have corrected those words in this paper.
Point 5: If there are not head differences, the wheel is not an undershot type, but a stream water wheel. See the previous reference.
Response 5: The authors are very grateful for reviewer’s suggestions. The undershot waterwheels are adapted to a lower head than others, sometimes they can be used for stream, so we called those water wheels as undershot water wheels improperly. However, the stream water wheels are more accurate obviously. We have corrected relevant mistakes.
Point 6: line 40: this is an example of sentence with bad English "because of its advantages with clean、renewable and abundant"
Response 6: The authors are very sorry for our negligence. We have edited the manuscript extensively. The sentence was corrected as "hydropower resources are valued by all over the world for its clean、renewable and abundant characteristics" in line 30. And, all revisions are highlighted using the "Track Changes" function in Microsoft Word and and some revisions are highlighted with yellow color.
Point 7: line 54: why? Overshot wheels do not need a curved shroud below them, like undershot and breastshot, thus they are apparently simpler....
Response 7: The authors are very grateful for reviewer’s suggestions. The authors think overshot water wheels are complicated because of applying to high heads based on requiring specially terrains, those terrains may be difficult to find. It maybe unclear, we have corrected relevant sentences in line 43-45. The sentences are corrected as "The overshot water wheels, which are recognized as the most effective traditional water wheels, they mainly make use of potential of water and are suitable for high heads".
Point 8: line 57: why "alternative"?
Response 8: The authors mean it is less effective than overshot water wheels, breast-shot water wheels are alternative if it requires relatively high efficiency without suitable terrain. It maybe unclear, we have corrected relevant sentences in line 46-47. The sentences are corrected as "The breast-shot water wheels are regards as a less effective than overshot water wheels and are mainly applied in smaller heads than overshot waterwheels".
Point 9: Line 60: the undershot wheel uses mainly the potential energy. It is the stream water wheel that uses the kinetic energy, see ref.15, and it can become an HPM at high blockage ratios.
Response 9: The authors are very sorry for our negligence. In ref.9, it said the undershot wheel for the exploitation of very small head differences was originally designed as an impulse wheel, employing the kinetic energy of the flow. However the authors ignore the most efficient shape for these wheels uses mainly the potential energy, we have corrected relevant sentences in line 48-49. The sentence is corrected as "The undershoot water wheels which are suitable for very low heads, are mainly employed potential energy of the water ".
Point 10: line 73: in ref.17, the optimal number of blades was 48, not 16, and a general equation was identified to generalize the results
Response 10: The authors are very sorry for our negligence in ref.17, we have corrected the relevant sentences in line 59-61. The sentence is corrected as "the results showed optimized shape had a more complicated design and those water wheels with 48-blades showed much higher efficiency than others".
Point 11: line 82: he did not test the Zuppinger type, but a stream wheel with blades similar to the Zuppinger type
Response 11: The authors are very sorry for our negligence, the stream wheel is used for tidal energy extraction in ref.20, we have corrected the relevant sentences in line 69-71. The sentences are corrected as " Manh Hung Nguyen et al. [20] compared the different performances with three blade shapes (straight, curved and the similar to Zuppinger type) through numerical experiments for a stream wheel".
Point 12: Line 84: like in ref.15, where the Sagebien wheel (straight blades) performed better than the Zuppinger type
Response 12: The authors are very sorry for our negligence. In line 72-73, the authors have cited this paper in this article and added some statements. We have added those "in addition, the same conclusion were made by Emanuele Quaranta et al. [15] ".
Point 13: Line 93: these results have been confirmed in Experimental Analysis of Effect of Canal Geometry and Water Levels on Rotary Hydrostatic Pressure Machine
Response 13: The authors are very grateful for reviewer’s suggestions. In line83-85, the authors have cited this paper in this manuscript and make some statements. We have added those "The similar experiments were conducted by Ilaria Butera et al [31], for a better performance, they suggested minimum distance between canal wall and the side of the wheel should be 0.3 times the width of the wheel".
Point 14: line 107: the k-omega model was also confirmed and used in ref.17
Response 14: The authors mean these recommendations are not final conclusions, because a good turbulent model is based on actual conditions. It may cause some unclear in manuscript, the authors have corrected the relevant sentences in line 100. We have added those "but it did not constitute a final conclusion".
Point 15: lines 128-134: example of very long and confusing sentence. Furthermore, it is a stream water wheel, because there is not a drop in the channel bed.
Response 15: The authors are very sorry for our negligence, we have edited the manuscript extensively. We have corrected relevant sentences in Line 115-119. The sentences are corrected as "The real-size stream water wheel is an 8-blades wheels with a straight type considered manufacture, the water level in river is 2.2m, the distance is 13m from gate to the center of water wheels, the distance between side walls is 11.4m, in order to make full use of kinetic energy, the water wheel is designed with wheel breadth of 11.0m, outer diameter D of 2.9m, the hub diameter d of 0.16m, side clearance of 0.2m. "
Point 16: line 153: add the mesh dimensions in mm and boundary layer mesh
Response 16: The authors are very grateful for reviewer’s suggestions, we have added some details according to reviewer’s suggestions in line 138-140. We have added those "In this case, flow domain’s mesh dimensions range between 0.23m to 0.12m and wheel domain’s mesh dimensions range between 0.12m to 0.07m, local mesh refinements were generated near blades". In addition, we have added the details of blades in figure 1.
Point 17: Chapter 3: the error on the efficiency/power measurement should be estimated
Response 17: The authors are very grateful for reviewer’s suggestions, the output and rotational speeds were measured by the GBM Power Station Control Center manufactured by GBM Co. Ltd, the water wheel is connected with axis of permanent magnet generator. The permanent magnet generator has very high efficiency and the high torque was generated by waterwheel, so maximum err on the power measurement is estimated within 2%. In line 226, we have added those "maximum err on the power measurement is estimated within 2%".
Point 18: line 231: "experimented considering natural environment" not clear
Response 18: The authors are very grateful for reviewer’s suggestions. Although it has been proved that environments effects may be minimal, we still afraid it may cause local ersion because of big waterwheel. It may cause some unclear in manuscript, the authors have corrected the relevant sentences in line 215. We have corrected the relevant sentences as "The case was experimented at immersed depth of 0.8m."
Point 19: why straight blades were used? As it can be seen in Fig.5, downstream water is uplift and a power loss is generated. Diagonal blades should be used, like in the hydrostatic pressure machine HPM. Add comments on this aspect
Response 19: The authors are very grateful for reviewer’s suggestions. The blade type was straight considered the manufacture, also we were lack of experience early. We will further our design in the future. We have added some details according to reviewer’s suggestion in line 115-116. The sentence is corrected as "The stream water wheel is an 8-blades wheel with a straight type considered manufacture".
Point 20: Fig.5: it is not clear if the upstream and downstream water levels are different, like in the HPM, or if are the same, like in stream water wheels.
Response 20: The upstream and downstream water levels are different, also the water level at different cases is different, the water level is discussed in Chapter 4.
Point 21: Angle instead of angel
Response 21: The authors are very sorry for our negligence, we have corrected relevant sentences. Also, we have edited the manuscript extensively.
Point 23: As the immersion increases, the blockage ratio increases and the upstream level increases, transforming the stream water wheel into an hydrostatic pressure machine. In the hydrostatic pressure machine, the wheel rotates not due to the kinetic energy, that is very small due to the high upstream water level, but due to the hydrostatic pressure related to the upstream-downstream head difference. This aspect should be better investigated, that is scientifically important, representing a transition between two kinds of wheels.
Response 23: The authors are very grateful for reviewer’s suggestions. The suggestions are really scientifically important. We will further our research in the near future for a water wheel with an optimal designed blade. In line 290-292, we have added some explanation as "In addition, the water wheel gradually becomes a HPM as growth of immersed depth, the transition is still need to be researched".
Point 24: Practical suggestions for the design should be drawn, and results compared with literature. Results should be generalized, as in the suggested reference, finding trends and similarity with other researches.
Response 24: The authors are very grateful for reviewer’s suggestions. Line 373-374, in conclusion, the suggestion is drawn as "It suggests that immersed depth with a radius ration of 82.74% can be applied for a much better performance".
Line 378-379, we have added some contents as "The water wheels mainly work at a low TSR for different cases, the result is consistent with ref.31".
Line 88-89, the guidelines was presented in ref. 37, we have added relevant the contents as "Emanuele Quaranta [37] presented the guidelines for stream water wheel.", in addition, the plan to be draw, we have added these contents as "the water wheel gradually becomes a HPM as growth of immersed depth, the transition is still need to be researched" in line 383-384.
Point 25: Nomenclature: add units
Response 25: The authors are very sorry for our negligence, we have corrected relevant mistakes.
The authors tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the all changes but all revisions are highlighted using the "Track Changes" function in Microsoft Word and some revisions are highlighted with yellow color..
We appreciate for Editors/Reviewers’ warm work honestly.
Once again, thank you very much for your comments and suggestions.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for Authors:
Manuscript ID water-733907
Title: Performance investigation of the immersed depth effects on water wheel using experimental and numerical analyses
The manuscript is a study about the performance and flow characteristics is investigated for undershoot water wheels suited for low and ultra-low heads in open channel.
This subject is particularly important due to the vast advance in this technology in the last years and the promising results of the current work. The method described in the present paper is simple but at the same time very useful. The scientific content could be higher but it is suitable for a high quality journal such as WATER. Some minor issues have to be addressed.
The objectives of the paper are not clearly described I recommend to the author to remark in a deeper way the reason and applications of the current investigation and to innovation/novelty/improvement with respect to other studies. The author have to show the originality of the present work.
The abstract is well written and organized; however, I consider too long and too many irrelevant details. Please, reduce the extension of the abstract.
INTRODUCTION: The introduction is well written and structured. A deep review of the state of the art is acutely described and explained. Line 68: the authors add 7 references with little explanations, please elaborate more. The same for line 89.
Figure 2 is nice for the mesh independency study. But I recommend to the aiuthors, the use of the Grid Convergence Index GCI of Roache , P. J. , 1998, “Verification and Validation in Computational Science and Engineering ,” Hermosa Publishers, Albuquerque, or the Richardson extrapolation method used in: Computational Modeling of Gurney Flaps and Microtabs by POD Method, Energies, Vol 11 DOI: 10.3390/en11082091
Paragraph of lines 118-125: this paragraph is too long, please define here clearly the main goals of the study.
Please, show also more pictures and parameters about the mesh (orthogonality, skewness, cell aspect ratio etc.)
Are equations 3, 5 7 8 and 9 necessary to include in the current paper? Are they a novelty? Have those equation been developed by the authors?
Section 5: Conclusion. They are well numbered and described in an exhaustive way. They are also well supported by the results. The objectives of the paper has to be included and shown before the conclusion, not in the conclusions.
Extensive English grammar and style revision is required!!!!
Author Response
Response to Reviewer 2 Comments
Thank you for your comments concerning our manuscript entitled “Performance investigation of the immersed depth effects on water wheel using experimental and numerical analyses” (Manuscript Number: water-733907). Those comments are all valuable and very helpful for revising and improving the paper to a better scientific level, as well as the important guiding significance to our researches. The authors have studied comments carefully and would like to make suitable revision for the present manuscript.
The main responds to the reviewers’ comments are as follows, please note that all revisions are highlighted using the "Track Changes" function in Microsoft Word and some revisions are highlighted with yellow color.
Point 1: The objectives of the paper are not clearly described, I recommend to the author to remark in a deeper way the reason and applications of the current investigation and to innovation/novelty/improvement with respect to other studies. The authors have to show the originality of the present work.
Response 1: The authors are very grateful for reviewer’s suggestions. This paper is concentrated on studying different immersed depths effects on water wheel’s performance and flow characteristics, we have made some revisions in Line 108-110, we have added some details as "So this paper is concentrated on studying different immersed depths effect on water wheel’s performance and flow characteristics through numerical simulations. This research conducted the experiments at immersed depth of 0.8m based on a real-size model."
Point 2: The abstract is well written and organized; however, I consider too long and too many irrelevant details. Please, reduce the extension of the abstract.
Response 2: The authors are very grateful for reviewer’s suggestions. We have corrected irrelevant details and make some revisions in Abstract.
Point 3: INTRODUCTION: The introduction is well written and structured. A deep review of the state of the art is acutely described and explained. Line 68: the authors add 7 references with little explanations, please elaborate more. The same for line 89.
Response 3: Lin68, all those references were from Emanuele Quaranta et al., they mainly researched performance of breast-shot and overshot water wheels coupling with different blade shapes, inflow configurations, and numbers of blades through simulations and experiments, also analysed the reasons of efficiency loss for overshot and breast-shot water wheels theoretically, they have an extensive study for breast-shot and overshot water wheels, the only main results are introduced in this manuscript. Line 89, those reference conducted a lot of researches for breast-shot and undershot water wheels, however, those researches cannot have a generalized conclusions, we have added some explanations as "those researches cannot have a generalized conclusions" in line 79.
Point 4: Figure 2 is nice for the mesh independency study. But I recommend to the aiuthors, the use of the Grid Convergence Index GCI of Roache , P. J. , 1998, “Verification and Validation in Computational Science and Engineering ,” Hermosa Publishers, Albuquerque, or the Richardson extrapolation method used in: Computational Modeling of Gurney Flaps and Microtabs by POD Method, Energies, Vol 11 DOI: 10.3390/en11082091
Response 4: The authors are very grateful for reviewer’s suggestions. Those methods are very nice for scientific researches, however, we need to study the methods in those paper, this methods will be adapted to in our next researches. We have added some details as "In this case, flow domain’s mesh dimensions range between 0.23m to 0.12m and wheel domain’s mesh dimensions range between 0.12m to 0.07m, local mesh refinements were generated near blades" in line 138-140.
Point 5: Please, show also more pictures and parameters about the mesh (orthogonality, skewness, cell aspect ratio etc.)
Response 5: The authors are very grateful for reviewer’s suggestions, We have some details as "In this case, flow domain’s mesh dimensions range between 0.23m to 0.12m and wheel domain’s mesh dimensions range between 0.12m to 0.07m, local mesh refinements were generated near blades" in line 138-140. Also, we have added the details of blades in figure 1.
Figure 1. Geometric model and grids of wheel domain
Point 6: Are equations 3, 5 7 8 and 9 necessary to include in the current paper? Are they a novelty? Have those equation been developed by the authors?
Response 6: The authors are very grateful for reviewer’s suggestions, those equations are not developed by authors, they are included in order to clarify the methods in this manuscript.
Point 7: Section 5: Conclusion. They are well numbered and described in an exhaustive way. They are also well supported by the results. The objectives of the paper have to be included and shown before the conclusion, not in the conclusions.
Response 7: The authors are very grateful for reviewer’s suggestions, we have added the purpose of this manuscript at Line 108-110. We have added some details as "So this paper is concentrated on studying different immersed depths effects on water wheel’s performance and flow characteristics through numerical simulations. This research conducted the experiments at immersed depth of 0.8m based a real-size model. The optimal immersed depth is identified. The results are expected to enhancing design and knowledge for undershoot and stream water wheels".
Point 8: Extensive English grammar and style revision is required!
Response 8: The authors are very grateful for reviewer’s suggestion. We have edited the manuscript extensively. All revisions are highlighted using the "Track Changes" function in Microsoft Word and some revisions are highlighted with yellow color.
The authors tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the all changes but all revisions are highlighted using the "Track Changes" function in Microsoft Word and some revisions are highlighted with yellow color.
We appreciate for Editors/Reviewers’ warm work honestly.
Once again, thank you very much for your comments and suggestions.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The paper was improved, but it was quite difficult to revise it because line numbers do not correspond to those written by Authors in the cover letter. For the next turn of review, I kindly ask to update them.
The Authors answered to my comments, but simply adding few lines in the manuscript, and without deeply considering them. I again suggest a major review hoping that the Authors will consider them in a comprehensive way, otherwise, if the paper remains as it is, it will give only isolated results that are not generalized and that can not be used in future researches, without adding scientific value. I am confident that the Authors will consider my comments, because they are studying an interesting topic that could give high scientific value.
Point 1: this should be discussed in the paper. Furthermore, when the immersed ratio becomes high, the wheel starts to operate based on the head difference, hence based on the potential energy (head difference, i.e. hydrostatic pressure). Therefore, if eq.2 is used, the Cp would become very high, because the term wM is very high (due to the hydrostatic force), but the kinentic energy at the denominator is extremely low, and results on Cp are hence not right. Therefore, I suggest that at the denominator of eq.2 the kinetic energy is used only for ratio a/D very low (see point 24). Therefore, I suggest to use not 0.5*rho*A*v3, but 0.5*rho*A*v3+rho*g*Q*deltaH, where Q=flow rate and deltaH=difference in water levels upstream-downstream
Point 7: also undershot and breastshot wheels mainly use the potential energy, differently from floating/stream wheels that mainly use the kinetic energy
Point 9: The undershoot water wheels which are suitable for very low heads, are mainly employed potential energy of the water ". I suggest to add a “,” after “wheels, and write “employ” instead of “are mainly employed”. Then, undershot instead of undershoot
Point 10: "the results showed optimized shape had a more complicated design and those water wheels with 48-blades showed much higher efficiency than others".
48 blades was the optimal number only for the wheel investigated in that paper, and this number is not valid in general. Therefore, results were generalized in order to provide equations that are valid in general, and that give the optimal number of blades (that can be different from 48) based on the hydraulic and geometric conditions. Specify better.
Point 15: “The real-size stream water wheel is an 8-blades wheels” to be modified into “…8-blades wheel”, without the “s”. Sometimes authors write water wheels, sometimes water wheel, and it is not clear if there are more wheels or one.
Point 16: add the value of y+ at the blade wall, and I suggest to take a reference length (like the wheel diameter), and also to present mesh dimensions both in mm (or m), as already rightly done, and as normalized to this reference length.
Point 17: all this description and justification should be also added in the manuscript, as for the other comments
Point 19: add this comment (my and your answer) in the manuscript for a better understanding
Point 23: in the manuscript, a clear definition of immersed ratio, or radius ratio, that is used throughout the manuscript, should be included by means of a proper equation. Furthermore, such a high radius ratio (82.74%) is very high: does it mean that the wheel is already in the field of the hydrostatic pressure machine (HPM) rather than in the stream wheel operation? Since Authors are investigating a transition phenomenon (very interesting and that needs more research), I suggest to define the immersed ratio as a/D, where a is the immersed length of the blade, and D the wheel diameter. This means that when a/D=0, the wheel does not interact with water (power equal to 0), and when a/D around 0.5, the upstream water level is at the level of the hub and the wheel is similar to an hydrostatic pressure machine. For each value of this ratio, the ratio a/h should also be added, where h is the downstream water depth. Indeed, the performance of stream wheels depend both on a/D (that means how much of the wheel interacts with water), and a/h that is the blockage ratio, a very useful parameter used also in hydrokinetic turbines (see refs. 35 and 37). In this paper, a/D changes, while a/h seems quite constant, but this should be specified, because future researches can investigate different a/h ratios and compare results with this paper.
Obviously, results here obtained at a certain a/h are valid in this specific case of a/h (where the water depth is very similar to the blade length). For example, if the flow depth would be 10 m (stream wheels in deep flow), an immersed ratio a/D=0.5 would not generate appreciable increase in the upstream water level. As you can see, all of my comments highlight as this research is dealing with a complex topic with different hints and scientific suggestions, but all of these comments are not deeply considered and discussed by the Authors.
I think that 2 radius ratio (or immersed ratio, depending on which definition the authors decide to use) should be identified: the first is when the wheel operates in the stream wheel operation, hence when the upstream water level remains below the hub. The optimal immersed ratio is that gives the optimal efficiency (or Cp, that in eq.2 should be explicitly defined power coefficient). The second optimal ratio is for operation as HPM: depending on upstream water level (hence depending on a/D) the power coefficient will have an optimal value at a certain value of a/D. In Butera et al. (2020), different upstream water levels were tested, and results should be compared.
line 60: undershot instead of undershoot
Fig 6: very important and useful figure, but in the legend also the immersed ratio (a/D) should be included for each value of immersed depth
line 513: remove “J E F S D”
Result generalization: Authors should compare their optimal a/D with other studies (that investigated a/D at a/h values different from this paper), giving useful insights about how a/D optimal is affected by a/h.
lines 393-397: results should be presented also in a normalized way as a function of a/D and a/h
."The water wheels mainly work at a low TSR for different cases, the result is consistent with ref. 31": quantitative values should be written and clear comparisons
Author Response
Thank you for your comments concerning our manuscript entitled “Performance investigation of the immersed depth effects on water wheel using experimental and numerical analyses” (Manuscript Number: Water-733907). Those comments are all valuable and very helpful for revising and improving the paper to a better scientific level, as well as the important guiding significance to our researches. The authors have studied comments carefully and would like to make suitable revisions for the present manuscript.
The main responds to the reviewers’ comments are as follows, please note that all revisions are highlighted using the "Track Changes" function in Microsoft Word and some revisions are highlighted with yellow color.
Point 1: this should be discussed in the paper. Furthermore, when the immersed ratio becomes high, the wheel starts to operate based on the head difference, hence based on the potential energy (head difference, i.e. hydrostatic pressure). Therefore, if eq.2 is used, the Cp would become very high, because the term wM is very high (due to the hydrostatic force), but the kinentic energy at the denominator is extremely low, and results on Cp are hence not right. Therefore, I suggest that at the denominator of eq.2 the kinetic energy is used only for ratio a/D very low (see point 24). Therefore, I suggest to use not 0.5*rho*A*v3, but 0.5*rho*A*v3+rho*g*Q*deltaH, where Q=flow rate and deltaH=difference in water levels upstream-downstream.
Response 1: The authors are very grateful for reviewer’s suggestions. We have seriously checked the cases and manuscript benefit from the reviewer’s suggestions. The stream wheel gradually becomes a RHPM because of the increasing of upstream water level, the kinetic energy is very low in front of the wheel, the potential energy is mainly used to drive the wheel, the eq.2 is loses its meaning just as the reviewer’s suggetions, so the eq.2 maybe caused some errs, after serious consideration, we think the eq.3 can better represent the power input, the eq.3 is cited in ref. 31, eq.3 is computed taking into account both the potential and kinetic components, also it is totally conform to Bernoulli theorem, so we decide to make a revision about how to calculate the Cp. As the reviewer’s suggestions, we cited the eq.3 in ref.31, it is really useful. The revisions are presented as follow in line 148-154.
"However, the stream wheel may gradually become a RHPM as growth of upstream water level, so the Cp should be defined as follow for RHPM [31]:
Where, = the swept area of the blades submerged in water (m^2 ), blade height (m), rotational speeds (rad/s), 9810 , and upstream and downstream water levels, and mean water velocities upstream and downstream, The velocities were calculated from the center of the water wheel to a distance of 2D. "
In addition, all the responses and revisions are seriously considered by authors, the contents are deleted or added in order to clearly expressing the meaning and improving the manuscript according the reviewer’s suggestions, we appreciate for editors and reviewers’ warm work honestly.
Those all revisions are highlighted using the "Track Changes" function in Microsoft Word, also, those revisions are highlighted with yellow color. However, in case of the line numbers do not correspond to those written by Authors in the cover letter (it may be caused by Microsoft Word Version), so the printscreen for some main revisions are presented.
Point 7: Also undershot and breastshot wheels mainly use the potential energy, differently from floating/stream wheels that mainly use the kinetic energy
Response 7: The authors are very grateful for reviewer’s suggestions. We have made some revisions benefit from reviewer’s suggestions, the summarized revisions are presented as Point 9.
Point 9: The undershoot water wheels which are suitable for very low heads, are mainly employed potential energy of the water ". I suggest to add a “,” after “wheels, and write “employ” instead of “are mainly employed”. Then, undershot instead of undershoot.
Response 9: The authors are very grateful for reviewer’s suggestions. Combined with Point 8 and Point 9, we make some revisions in line 41-41 benefit from reviewer’s suggestions. In line 44-41, after "four main kinds of water wheels models are overshot, breast-shot, undershot and stream [9-11] " in manuscript, we firstly introduce that different water wheels use kinetic energy or potential energy as presented "The stream wheels mainly uses kinetic energy, and the others mainly make use of potential of water" in line 41-42, after that, we introduced something about heads, efficiency and so on for different water wheels. In addition, in order to keep consistent with the manuscript’s structure, after line 43-44, we have deleted those contents about utilization of energy for water wheels. Those deleted contents can be found using "Track Changes" function in Microsoft Word. Also, the authors are very sorry for our negligence, we have corrected the spelling mistakes.
The printscreen for some main revisions are presented.
Point 10: "the results showed optimized shape had a more complicated design and those water wheels with 48-blades showed much higher efficiency than others".
48 blades was the optimal number only for the wheel investigated in that paper, and this number is not valid in general. Therefore, results were generalized in order to provide equations that are valid in general, and that give the optimal number of blades (that can be different from 48) based on the hydraulic and geometric conditions. Specify better.
Response 10: The authors are very sorry for our negligence, the generalized results are usually more important, thank to reviewer’s suggestions, in order to specify the results, we have added some relevant contents, the specific contents are presented as "furthermore, the equations about optimal number of blades were generalized based on the hydraulic and geometric conditions" in line 60-61.
The printscreen for some main revisions are presented.
Point 15: “The real-size stream water wheel is an 8-blades wheels” to be modified into “…8-blades wheel”, without the “s”. Sometimes authors write water wheels, sometimes water wheel, and it is not clear if there are more wheels or one.
Response 15: The authors are very sorry for our negligence, we have reviewed the manuscript again and corrected the relevant contents that manuscript cannot express meaning clearly.
Point 16: add the value of y+ at the blade wall, and I suggest to take a reference length (like the wheel diameter), and also to present mesh dimensions both in mm (or m), as already rightly done, and as normalized to this reference length.
Response 16: The authors are very grateful for reviewer’s suggestions. Y+ is a very important value in numerical simulation, thank to reviewer’s suggestions, the relevant contents about Y+ are presented " also, Y+, a non-dimensional wall distance, is about 34 at the blades." in line 138-141. Furthermore, thanks to reviewer’s suggestion, relative values of mesh dimensions are presented in order to specify the mesh dimensions, the reference length is the wheel diameter, those relative values usually are important for calculation, in line 138-141, those details are presented as" So this number of the elements is chosen for different cases. In this case, flow domain’s mesh dimensions range between 0.23m (0.021D) to 0.12m (0.011D) and wheel domain’s mesh dimensions range between 0.12m (0.011D) to 0.07m (0.006D)," .
The printscreen for some main revisions are presented.
Point 17: all this description and justification should be also added in the manuscript, as for the other comments
Response 17: The authors are very grateful for reviewer’s suggestions. In line 239-240, the relevant contents are presented as "The permanent magnet generator has very high efficiency and the high torque was generated, the maximum err on the power measurement is estimated within 2% ". In addition, we have made some reversions in manuscript for other comments.
The printscreen for some main revisions are presented.
Point 19: add this comment (my and your answer) in the manuscript for a better understanding
Response 19: The authors are very grateful for reviewer’s suggestions. The comment has significant significance for future research, in line 114-115, the relevant contents are presented as "The real-size stream water wheel is an 8-blades wheel with a straight type considered simple manufacture, diagonal blades will be designed for a better performance in the next researches."
The printscreen for some main revisions are presented.
Point 23: in the manuscript, a clear definition of immersed ratio, or radius ratio, that is used throughout the manuscript, should be included by means of a proper equation. Furthermore, such a high radius ratio (82.74%) is very high: does it mean that the wheel is already in the field of the hydrostatic pressure machine (HPM) rather than in the stream wheel operation? Since Authors are investigating a transition phenomenon (very interesting and that needs more research), I suggest to define the immersed ratio as a/D, where a is the immersed length of the blade, and D the wheel diameter. This means that when a/D=0, the wheel does not interact with water (power equal to 0), and when a/D around 0.5, the upstream water level is at the level of the hub and the wheel is similar to an hydrostatic pressure machine. For each value of this ratio, the ratio a/h should also be added, where h is the downstream water depth. Indeed, the performance of stream wheels depend both on a/D (that means how much of the wheel interacts with water), and a/h that is the blockage ratio, a very useful parameter used also in hydrokinetic turbines (see refs. 35 and 37). In this paper, a/D changes, while a/h seems quite constant, but this should be specified, because future researches can investigate different a/h ratios and compare results with this paper.
Obviously, results here obtained at a certain a/h are valid in this specific case of a/h (where the water depth is very similar to the blade length). For example, if the flow depth would be 10 m (stream wheels in deep flow), an immersed ratio a/D=0.5 would not generate appreciable increase in the upstream water level. As you can see, all of my comments highlight as this research is dealing with a complex topic with different hints and scientific suggestions, but all of these comments are not deeply considered and discussed by the Authors.
I think that 2 radius ratio (or immersed ratio, depending on which definition the authors decide to use) should be identified: the first is when the wheel operates in the stream wheel operation, hence when the upstream water level remains below the hub. The optimal immersed ratio is that gives the optimal efficiency (or Cp, that in eq.2 should be explicitly defined power coefficient). The second optimal ratio is for operation as HPM: depending on upstream water level (hence depending on a/D) the power coefficient will have an optimal value at a certain value of a/D. In Butera et al. (2020), different upstream water levels were tested, and results should be compared.
Response: The authors are very grateful for reviewer’s suggestions. In order to clear the meaning of immersed radius ration, we add the diagram in fig.3. In our research, we are concentrated on studying different immersed depths effect on water wheel’s performance, it means the optimal immersed depth is expected to be ensured in a stream that the water level between upstream and downstream is very low or equal when it is not equipped with wheel, based on this, we want to ensure the immersed depth when the wheel have a better performance, so the immersed radius ratio h/r is defined in line 220-221, the immersed depth h is the controlled variable and is our objective in our researches, meanwhile, our all results is about the relationship between the immersed depth and water level, output, efficiency, velocity and so on. However the variable like the downstream water level, it changes mainly because of the changes of immersed depth, its change certainly is related with the wheel’s performance, but downstream water level is depend on immersed depth in this research, it is not a controlled variable in this research (the difference is that the upstream water level or upstream water level is a controlled variable in ref.31), so all results that we generalized are contents about the different immersed depths. Also the point about blockage ratio has the high scientific value, however, it should be conducted much more researches to specific the different blockage ratios effect on wheel’s performance, our objective is to research different immersed depth effect on wheel’s performance, although the blockage ratio has high scientific value as reviewer’s suggestions, we still cannot give valid results about the blockage ratio.
In line 220-221, the define of immersed radius ration are presented as "In addition, the immersed radius ration was defined as h/r, the h represents the immersed depth and r is D/2"
The printscreen for some main revisions are presented.
We have seriously checked the manuscripts benefit from the reviewer’s suggestions, we defined 2 different Cp according reviewer’s suggestions, the different Cp is defined according different upstream water level, the Cp in RHPM is used when the upstream water level is above the hub as the reviewer’s suggestion, in contrast, the Cp in stream wheel is used. However, we are more concentrate on the immersed depth effect on wheel’s performance, the transition is still need much more researches, the cases about transition need much more detail and cases to be calculated, so here we can give the generalized results about different immersed depth, the transition will be researched in the next research. The waterwheel is still need much more researches, because there are many factors may effect wheel’s performance. Benefit from the reviewer’s suggestions, we have made revisions in manuscripts.
Figure 3. Boundary condition and diagram of water wheel operation
Also, in order to clear the results, we have generalized the results for stream wheel and RHPM according the reviewer’s suggestion, however, we focus on the immersed depth effect on water wheel’s performance, so the details about transition from stream wheel to RHPM cannot be generalized in this research, we think that the details about transition need much more researches.
In line148-154, the define about Cp is present as "However, the stream wheel may gradually become a HPM as growth of upstream water level, so the Cp should be defined as follow for HPM [31]:
Where, = the swept area of the blades submerged in water ( ), blade height (m), rotational speeds (rad/s), 9810 , and upstream and downstream water levels, and mean water velocities upstream and downstream, The velocities were calculated from the center of the water wheel to a distance of 2D. "
The printscreen for some main revisions are presented.
In line 258-263, the main revisions about Cp are presented as "The different cases are researched at different immersed depths. The Cp is evaluated using Eq.2 when the upstream water level remains below the hub and Cp is evaluated using Eq.3 when the upstream water level remains above the hub. More specially, when the immersed radius ration is 68.96% (1.0m), the upstream water levels is varied around the center of hub at low rotational speeds, this immersed radius ration can be considered a transition from stream water wheel to HPM, here Cp is evaluated using Eq.2. The performance of Cp is shown as figure 6.".
The printscreen for some main revisions are presented.
line 60: undershot instead of undershoot
Response: The authors are very sorry for our negligence, we have corrected the spelling mistakes.
Fig 6: very important and useful figure, but in the legend also the immersed ratio (a/D) should be included for each value of immersed depth
Response: The authors are very grateful for reviewer’s suggestions. As the reviewer’s suggestions, we have defined a Cp for RHPM (Specific contents are presented in Response 1), and we have also made revisions in fig.6. The fig.6 is presented as follow in line 256.
Figure 6. Comparison of Cp among different immersed depth
line 513: remove “J E F S D”
Response: The authors are very sorry for our negligence, we have corrected the relevant contents in line 511.
The printscreen for some main revisions are presented.
Result generalization: Authors should compare their optimal a/D with other studies (that investigated a/D at a/h values different from this paper), giving useful insights about how a/D optimal is affected by a/h.
Response: The authors are very grateful for reviewer’s suggestions. This research is concentrated on studying different immersed depths effect on water wheel’s performance and flow characteristics through numerical simulations, Just like the reviewer’s suggestions, there still need much more researches about the transition, the blockage ratio and so on, however, the research is expected to ensure an optimal immersed depth for stream wheel (here they are all called the stream wheel ignored the transition), the upstream water level is elevated because of the growth of the immersed radius ration, the upstream level is not a controlled variable like ref.31, so we can give the results that the relationship between the water level ( ) and immersed radius ration. However, the blockage ratio (a/h) is still need much more researches, also the topic about the transition from stream wheel to RHPM, those suggestions are dealing with a complex topic like the reviewer’s suggestions, we think it has high scientific value, but it need much more researches about those topic to discuss they. We are very grateful for reviewer’s suggestions, the more researches need to be done in the future, also we will develop it in the next research. The optimal immersed depth is expected to be ensured in a stream that the water level between upstream and downstream is very low or equal when it is not equipped with wheel, the immersed radius ration (h/r) has some differences with ref.31 in this research, the h means the wheel’s blade immersed depth when the stream is not equipped with wheel, the h in ref.31 means the upstream water level, so we have generalized the results, in line 386-393, the generalized results are presented as"The water wheel’s performance is much better as the increasing of immersed radius ratio as stream wheel before immersed radius ration 68.96% (1.0m), after that, the water wheel at the immersed radius ratio of 82.76% (1.2m) perform the best performance as RHPM in all cases. The case at immersed radius of 82.74% shows the best performance, achieves a maximum efficiency of 18.05% at TSR 0.1984. The maximum efficiency is followed by 16.98% at the immersed radius ration 68.96%, 12.69% at the immersed radius ration 55.17%, and 8.6% at immersed radius ration 41.37% with all TSR 0.1984. It suggests that immersed depth at immersed radius ration of 82.74% can be applied for a much better performance.".
The printscreen for some main revisions are presented.
In addition, the some useful topics are suggested in the next researches in line 402-404. The contents are presented as "In addition, the case at the immersed radius ration 68.96% is a transition from stream wheel to RHPM, after that case, the wheel becomes a RHPM, furthermore, the transition is still need to be more researches."
The printscreen for some main revisions are presented.
lines 393-397: results should be presented also in a normalized way as a function of a/D and a/h
Response: The authors are very grateful for reviewer’s suggestions. In line 386-393, the normalized results usually have significant significance, so we make normalized results as "The water wheel’s performance is much better as the increasing of immersed radius ratio as stream wheel before immersed radius ration 68.96% (1.0m), after that, the water wheel at the immersed radius ratio of 82.76% (1.2m) perform the best performance as RHPM in all cases. The case at immersed radius of 82.74% shows the best performance, achieves a maximum efficiency of 18.05% at TSR 0.1984. The maximum efficiency is followed by 16.98% at the immersed radius ration 68.96%, 12.69% at the immersed radius ration 55.17%, and 8.6% at immersed radius ration 41.37% with all TSR 0.1984. It suggests that immersed depth at immersed radius ration of 82.74% can be applied for a much better performance.".
The printscreen for some main revisions are presented.
"The water wheels mainly work at a low TSR for different cases, the result is consistent with ref. 31": quantitative values should be written and clear comparisons
Response: The authors are very grateful for reviewer’s suggestions. In line 396-398, we have made some revisions as "The water wheels mainly work at a low TSR for different cases, it is TSR<0.1984, also, the wheel has a higher efficiency at <0.2 (the TSR is equal to ) in ref.31, it can be said the results is consistent with each other." We believe they are very useful for improving our manuscript".
The printscreen for some main revisions are presented.
The authors tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the all changes but all revisions are highlighted using the "Track Changes" function in Microsoft Word and some revisions are highlighted with yellow color..
We appreciate for Editors and Reviewers’ warm work honestly.
Once again, thank you very much for your comments and suggestions.
Author Response File: Author Response.docx
Round 3
Reviewer 1 Report
The Authors answered to most of my comments and the paper was improved. I would like to suggest some comments to make the paper clear. The paper is approaching the final version to be considered for publication, but some points have to be addressed.
a) Equations 2 and 3 are both called equation 2.
b) Response 1: ok, but when eq.2 is used, the new result is called efficiency, not power coefficient (see ref.37). Power coefficient is used when the kinetic energy is used (eq.2), efficiency is used when all the head difference is used (eq.3). Specify this better after Eq.3.
c) Response 23: “Also the point about blockage ratio has the high scientific value, however, it should be conducted much more researches to specific the different blockage ratios effect on wheel’s performance”
The immersed depth is strictly related to blockage ratio, and Authors have already investigated also the wheel at different blockage ratio, but maybe they do not notice this.
The immersed depth is h/r, while the blockage ratio is h*b/(t*B), where b is the blade width (fixed), while t=undisturbed flow depth (fixed) and B=channel width (fixed). Therefore, implicitly, Authors have already investigated also the wheel at different blockage ratios. the value of t can be taken as equal to the downstream depth for more accuracy.
d) This suggestion is related to Fig.6: the optimal Cp is at TSR=0.2. The optimal Cp should be plotted versus immersed ratio in order to find how it increases, and then also versus the blockage ratio.
e) It would be interesting also to plot the immersed ratio versus the blockage ratio. Authors already have these data, thus they only need to better analyse them.
f) line 225: ratio instead of ration
g) Fig.3: h is the immersed depth. When the upstream water level is above the hub, the immersed depth is referred to the downstream water level (that is almost constant when the immersed depth changes) or to the upstream water level? Specify better.
h) Specify better when you passed from using eq.2 to eq.3. For example, the wheel passes from the stream type to the RHPM type when P_head/P_kin > X, where P_head is the power input related to the head difference h1-h2 (P_head=9810*Q*(h1-h2)), while P_kin is the kinetic energy as defined in eq.2. There is not a precise value of X, but, in a first approximation, I suggest to use X=1. Therefore, a table should be added with the following columns: immersed depth, immersed ratio, blockage ratio, X, and when X>1 this means that the wheel is more similar to an RHPM. I am open to discuss with Authors and also to know their point of view.
i) Fig.6 : I suggest to split it into Fig.6a and Fig.6b. In Fig.6a the Cp is calculated always with Eq.2, while in Fig.6b the Cp is calculated with eq.2 for X<1 and Eq.3 for X>1 (as the present Fig.6).
l) Fig.10 is in the reverse sense with respect to the other figures, and it must be adapted and presented as the other pictures
m) Specify that these tests refer to a specific blockage ratio, defined as h*b/(t*B), where h is the immersed depth, b is the blade width, t=undisturbed flow depth and B=channel width. Therefore, as the immersed ratio changes (h changes), also the blockage ratio changes. Therefore, Authors own a lot of results that are not well considered. There is not the need of future researches as they claim, because results are already shown, but not in a clear way.
Author Response
Response to Reviewer 1 Comments
Thank you for your comments concerning our manuscript entitled “Performance investigation of the immersed depth effects on water wheel using experimental and numerical analyses” (Manuscript Number: Water-733907). Those comments are all valuable and very helpful for revising and improving the paper to a better scientific level, as well as the important guiding significance to our researches. The authors have studied comments carefully and would like to make suitable revisions for the present manuscript.
The main responds to the reviewers’ comments are as follows, please note that all revisions are highlighted using the "Track Changes" function in Microsoft Word and some revisions are highlighted with yellow color.
Point a: Equations 2 and 3 are both called equation 2.
Response a: The authors are very grateful for reviewer’s suggestions. The main summarized revisions are presented as Point b.
In addition, in case of the line numbers do not correspond to those written by Authors in the cover letter (it may be caused by Microsoft Word Version), so the printscreen for some main revisions are presented.
Point b: Response 1: ok, but when eq.2 is used, the new result is called efficiency, not power coefficient (see ref.37). Power coefficient is used when the kinetic energy is used (eq.2), efficiency is used when all the head difference is used (eq.3). Specify this better after Eq.3.
Response b: The authors are very grateful for reviewer’s suggestions. We are very sorry for our negligence, although the both two parameters are used to evaluated to wheel’s performance, we ignored that the parameters had some differences at using different type energy like reviewer’s suggestions, we have made some revisions to clear the differences between those two parameters benefit from reviewer’s suggestions. In line 148-150, the relevant contents are presented as "The power coefficient is used when the kinetic energy is used, however, the stream wheel may gradually become a RHPM as growth of upstream water level. The efficiency is used when all the head differences are used, efficiency is defined as follow for RHPM [31,37]:".
The printscreen for main revisions are presented as follow.
Point c: Response 23: “Also the point about blockage ratio has the high scientific value, however, it should be conducted much more researches to specific the different blockage ratios effect on wheel’s performance”
The immersed depth is strictly related to blockage ratio, and Authors have already investigated also the wheel at different blockage ratio, but maybe they do not notice this.
The immersed depth is h/r, while the blockage ratio is h*b/(t*B), where b is the blade width (fixed), while t=undisturbed flow depth (fixed) and B=channel width (fixed). Therefore, implicitly, Authors have already investigated also the wheel at different blockage ratios. the value of t can be taken as equal to the downstream depth for more accuracy.
Response c: The authors are very grateful for reviewer’s suggestions. The immersed depth is strictly related to blockage ratio, actually those topics are always related to blockage ratio more or less once those topics involve the water level, immersed depth, practical stalled location and so on, those researches are certainly related to blockage ratio in manuscript, but we thought the length of a blade may need to be much longer with a blade can be nearly totally immersed to research the blockage ratio, so that the much more cases and details about the blockage ratio can be researched rather than the present blades, however, we are expected to ensure an optimal immersed depth for practical engineering (to some extent, it has some differences with blockage ratio in practical engineering), the immersed depth (immersed radius ratio) maybe more visualized when the wheel is required to be built and stalled at an optimal immersed depth considering the specific size. However, the blockage ratio has really significant significance and high scientific value like reviewer’s suggestions, it has more generalized significance. Like reviewer’s suggestions, the blockage ratio changes as the change of immersed depth, so in line 229-232, the define of blockage ratio are presented "In addition, the blockage ratio is used to specify the immersed radius ratio effect on wheel’s performance [35,37], the blockage ratio is defined as h*b/(t*B), where b is the blade width (11m), t is undisturbed flow depth (2.2m) and B= channel width (11.4m)."Also the Table included immersed depth, immersed ratio, blockage ratio and X, is presented, those parameters are presented in order to provide the details for others researchers and future researches. The main revisions are presented in Point h
The printscreen for some main revisions are presented as follow.
Point d: This suggestion is related to Fig.6: the optimal Cp is at TSR=0.2. The optimal Cp should be plotted versus immersed ratio in order to find how it increases, and then also versus the blockage ratio.
Response d: The authors are very grateful for reviewer’s suggestions. The represented of optimal Cp is good for manufacturing a serialization of products for different capacity and characterize the wheel’s characteristics. The figure for the optimal Cp is plotted versus immersed ratio in order to find how it increases benefit reviewer’s suggestions, the figure is presented as figure 6 (b).The topic about blockage ratio as response c presented, the table included some parameters such as blockage ratio are presented as table 2 to provide the details for others researchers and future researches, in line 284-286, some results are presented as " In addition, it can be found that the optimal is steady growth before the transition, however, after that, the optimal begins to increase at a lower rate until immersed radius ratio 82.76%."
The printscreen for some main revisions are presented as follow.
The figure 6 are presented in line 276-277.
Figure 6. The and optimal among different immersed radius ratios
The printscreen for some main revisions are presented as follow.
Point e: It would be interesting also to plot the immersed ratio versus the blockage ratio. Authors already have these data, thus they only need to better analyse them.
Response e: The authors are very grateful for reviewer’s suggestions. The blockage ratio changes as the change of immersed radius ratio, and they are only related to wheel’s specific size, the relationship between them should be functional, we are more concentrated on the topic about immersed depth, so the table about the immersed radius ratio and blockage ratio are presented as Table 2 for other researchers and future researches in line 267.
Table 2. The main characteristic parameter
The printscreen for some main revisions are presented as follow.
Point f: line 225: ratio instead of ration
Response f: The authors are very sorry for our negligence, we have seriously reviewed the manuscript again and corrected the relevant contents to improve the editing of English language. We are very grateful for reviewer’s suggestions.
Point g: Fig.3: h is the immersed depth. When the upstream water level is above the hub, the immersed depth is referred to the downstream water level (that is almost constant when the immersed depth changes) or to the upstream water level? Specify better.
Response g: The authors are very grateful for reviewer’s suggestions. After consideration, We also think it is unclear in manuscript like reviewer’s suggestions, the h is mean that it is referred to the immersed depth when wheel is stalled at an undisturbed flow depth and it is only related with the high between the installed location and free surface at undisturbed flow depth, in other words, the h represents the immersed depth when the stream is not equipped with wheel, in order to clarify it, in line 228-229 ,the revisions are presented as "the h represents the immersed depth when the stream is not equipped with wheel "
The printscreen for main revisions are presented as follow.
Point h: Specify better when you passed from using eq.2 to eq.3. For example, the wheel passes from the stream type to the RHPM type when P_head/P_kin > X, where P_head is the power input related to the head difference h1-h2 (P_head=9810*Q*(h1-h2)), while P_kin is the kinetic energy as defined in eq.2. There is not a precise value of X, but, in a first approximation, I suggest to use X=1. Therefore, a table should be added with the following columns: immersed depth, immersed ratio, blockage ratio, X, and when X>1 this means that the wheel is more similar to an RHPM. I am open to discuss with Authors and also to know their point of view.
Response h: The authors are very grateful for reviewer’s suggestions. The transition from stream wheel to RHPM still needs to be researched, but reviewer’s suggestions are regarded as very significant significance, a non-dimensional parameter X is defined benefit from reviewer’s suggestions, the parameter X is defined according the ratio of potential energy to kinetic energy like reviewer’s suggestions. In addition, the main characteristics parameters are presented as Table 2 for other researchers and future researches.
In line 160-166, the define of X are presented as" In order to specify the transition from stream wheel to RHPM, a non-dimensional parameter X is defined, means that the wheel is more similar to an RHPM, means that the wheel is more similar to an stream wheel, means that the wheel is the transition from stream wheel to RHPM, the is defined as follow:
Where, is the potential energy between upstream and downstream, is the is the kinetic energy"
The printscreen for main revisions are presented as follow.
The table 2 are presented as follow in line 267:
Table 2. The main characteristic parameter
The printscreen for main revisions are presented as follow.
Point i: Fig.6 : I suggest to split it into Fig.6a and Fig.6b. In Fig.6a the Cp is calculated always with Eq.2, while in Fig.6b the Cp is calculated with eq.2 for X<1 and Eq.3 for X>1 (as the present Fig.6).
Response i: The authors are very grateful for reviewer’s suggestions. The power coefficient Cp and efficiency are presented in figure 6, the more contents about figure 6 can be seen in Point d, the optimal Cp at different immersed radius ratio are presented as figure6 (b), the wheel’s performance is presented in figure 6 (a). The comparison Cp with different definitions maybe a scientific topic, but they are not our main topic.
Point l: Fig.10 is in the reverse sense with respect to the other figures, and it must be adapted and presented as the other pictures
Response l: The authors are very grateful for reviewer’s suggestions. In order to adapted the figures’ structure in manuscript, in line 344-345 ,we have make some versions to presented that the fig.10 in the same sense with respect to other figures benefit from reviewer’s suggestions.
The printscreen for the revisions is presented as follow.
Point m: Specify that these tests refer to a specific blockage ratio, defined as h*b/(t*B), where h is the immersed depth, b is the blade width, t=undisturbed flow depth and B=channel width. Therefore, as the immersed ratio changes (h changes), also the blockage ratio changes. Therefore, Authors own a lot of results that are not well considered. There is not the need of future researches as they claim, because results are already shown, but not in a clear way.
Response m: The authors are very grateful for reviewer’s suggestions. The topic about blockage ratio can be seen in Point c. In order to specify the blockage ratio, the specify definition are presented benefit from reviewer’s suggestions, in line 229-232, the relevant contents are presented as " In addition, the blockage ratio is used to specify the immersed radius ratio effect on wheel’s performance [35,37], the blockage ratio is defined as h*b/(t*B), where b is the blade width (11m), t is undisturbed flow depth (2.2m) and B= channel width (11.4m)."
The printscreen for the revisions is presented as follow.
The authors tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the all changes but all revisions are highlighted using the "Track Changes" function in Microsoft Word and some revisions are highlighted with yellow color.
We appreciate for Editors and Reviewers’ warm work honestly.
Once again, thank you very much for your comments and suggestions.
Author Response File: Author Response.docx
