Effects of Slotted Blades on the Hydrodynamic Performance of Horizontal Axis Tidal Turbines

Round 1

Reviewer 1 Report

In this study, slots were applied to horizontal axis turbine blades to analyze their effects on hydraulic performance. The effect of slot exit position and width, and slot length on hydraulic performance was analyzed through numerical analysis. Although structural design needs to be additionally considered to apply this technology, it will be applicable as an advanced technology for improving the hydrodynamic performance of turbines in the future. Based on the minor comments below, it is recommended that a revised version be published in the JMSE journal.

 

1. 4 page

Modify the equation because CP in Equation 4 is proportional to the cube of the velocity.

 

2. 5page

Based on the results of the grid dependence test, about 3.5 million grids were selected as the optimal grid, but a difference of 5% is considered a large error in evaluating the results. Rather, 5 million grids are judged to be a more reasonable grid size.

 

3. 5 page

An experiment was conducted to verify the reliability of numerical analysis. What was the reference standard for performing the experiment? Performance evaluation of the tidal current energy converter should be performed with reference to IEC TS 62600-200 or 202.

 

4. ‘4.3 Analysis of the passive fluid control mechanism of the slot’

What is the criterion for evaluating stall in numerical analysis?

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

General comments:

Very interesting paper. However, an overview of the characteristic changes of slot position and size as well as the extent of this investigation would be helpful to give an overview of the extent of the study (preferably before the experimental results are described).

The authors mentioned any papers in literature with similar investigations. Why are no result comparisons or references to literature findings mentioned in the analysis and results?

Also it would be helpful to know who the authors decided on the design tested in the study. Was this a random choice or did it stem from literature findings and if so, which ones

 

Specific comments:

Correct line 40 “slat”

Line 61-62 sentence structure should be corrected

Line 72 “ blockage due..” or “caused”

Line 91- Why was the slot applied here? Where did this design come from .

Line 112- An accurate method? It is a theoretical approximation. Recommend removing the word accurate. This is at most an acceptable replication of true conditions and if this is said a previous reference with accuracy of approximation should be quoted.

Line 126- this is a significant effect, why not 5 million? How was this deemed acceptable? Was any visual analysis done on the effects captured in a smaller mesh that may have been crucial to the study?

Line 129 , 157 replace “accuracy” to “acceptability” and define the tolerance

Line 129-130 sentence structure should be corrected

Line 213- sentence structure should be corrected

Line 228- why these values for exit width and length?

Line 134- define blockage ratio

Fix refs, should contain et al. if more than 1 author is referenced.

English language requires some improvements (with regard to sentence structure). 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

- The abstract should state briefly the purpose of the research, the principal results and major conclusions. An abstract is often presented separately from the article, so it must be able to stand alone.

- More suitable title should be selected for the figure 3 instead of “Installation drawing of turbine torque test device.”.

- The major defect of this study is the debate or Argument is not clear stated in the introduction session. Hence, the contribution is weak in this manuscript. I would suggest the author to enhance your theoretical discussion and arrives your debate or argument.

- Using the article entitled "Yamini et al. Hydraulic Performance of Seawater Intake System Using CFD Modeling", discuss regarding the formation of vortices at the entrance.

- It is mentioned that “The turbulence term of the RANS equation is simulated by the SST k-ω turbulence model, which has been widely used….”. The authors should explain the reason for choosing the turbulence model in the numerical model?

- The material and method divisions are not well done and not explain the details of the work. It is better to give necessary and important information. The method of doing the work is not clear enough. Describe the year of the experiment, how the data was collected, and how the work was performed. Or make a flowchart of how to do it for the Materials and Methods section. The content of this section is not sufficient.

- Calibration and validation of the results should be given more attention by the authors.

- For the Fig. 15. Pressure contours of different slotted blades (TSR=3) Provide explanations and comparison of different conditions.

- All symbols and parameters should be defined, please check.

- Draw a flowchart from your workflow that briefly shows the process of the methodology.

- Page 10: the following paragraph is unclear, so please reorganize that:

“The influence of the slot on the hydrofoil flow field depends to a large extent on its geometric parameters. As the slot's exit position gets closer to the transition point, its suppression of the flow separation of the hydrofoil becomes better. For example, when the exit position is at 0.35c, compared to the clear hydrofoil, the flow separation of the slotted hydrofoils is obviously suppressed. Similarly, as the slot exit width is larger, the hydrofoil flow separation suppression effect is better. This is because the more significant the exit width of the slot, the greater the fluid momentum injected into the hydrofoil suction surface from the hydrofoil pressure surface.”

- It is suggested to add articles entitled “Sazonov et al. Computational Fluid Dynamics (CFD) Simulation of Mesh Jet Devices for Promising Energy-Saving Technologies” and “Sazonov et al. Designing Mesh Turbomachinery with the Development of Euler’s Ideas and Investigating Flow Distribution Characteristics” to the literature review.

- Please make sure your conclusions' section underscore the scientific value added of your paper, and/or the applicability of your findings/results, as indicated previously. Please revise your conclusion part into more details. Basically, you should enhance your contributions, limitations, underscore the scientific value added of your paper, and/or the applicability of your findings/results and future study in this session.

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

The authors presented a numerical study on the Effects of Slotted Blades on the Hydrodynamic Performance of Horizontal Axis Tidal Turbines.

The main quantitative findings are to be mentioned in the abstract.

The solved governing equations are to be presented.

The boundary conditions are to be expressed mathematically.

The used turbulence model is to be justified.

What is the range of Re corresponding to the considered cases?

What are the dimensions of the computational domain? To be justified.

Information about the characteristics of the used computer and the computational time are to be provided.

What is the convergence criterion?

What is the time step?

A qualitative verification (2D or 3D flow structure for example) of the numerical model is to be performed by comparing with previously published numerical results.

The 3D flow structure (streamlines) is to be presented.

The discussion is to be improved by adding physical interpretations.

English level needs to be improved.

  

English level needs to be improved.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 5 Report

The manuscript is interesting but it should consider other references inwhich researches analyzes the behaviour of turbines, as example

Assessment  of  wind  power  potential  and  economic  analysis  at  Hyderabad  in  Pakistan:  Powering  to  local  communities  using  wind  power.  Sustainability,  11(5),  1391.  https://doi.org/10.3390/su11051391

Parametric study of a horizontal axis wind turbine with similar characteristics to those of the Villonaco wind power plant. J Appl Res Eng Technol & Engineering, 2(2), 51-62. https://doi.org/10.4995/jarte.2021.15056

Application  of  the  BEM  Theory  to  Design  HAWT  Blades.  Journal of Solar Energy Engineering, Transactions of the ASME, 140(1), 014501. https://doi.org/10.1115/1.4038046

 

The manuscript should analyse the error compared with simulation and experimental

The authors shows different figures but they did not discuss only enumareted. Please, the figures should be discussed deeply compared with other published researches.

The conclusions should show the novel, future lines as well as the application in real case studies. 

Minor checks should be reviewed

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The manuscript revised very well, so I would recommend to accept in its present form.

Reviewer 5 Report

The authors answered correctly the different suggestions.