An Optimization Study on the Hull Form and Stern Appendage for Improving Resistance Performance of a Coastal Fishing Vessel

Round 1

Reviewer 1 Report

The comments are included in the attached file.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 1

 

Manuscript ID: applsci-1271997

Type of manuscript: Article

Title: An optimization study on the hull form and stern appendage for improving resistance performance of a coastal fishing vessel

Authors: Jin-Won Yu, Min Kyung Lee, Yang-Ik Kim, Sung-Bu Suh, Inwon Lee*

 

Before acceptance, the following issues should be addressed properly.

• We are thankful to the reviewer for the constructive comments. In preparing for the revised manuscript, we have attempted to incorporate faithfully the suggestions of reviewer. Several sentences, marked red, have been either inserted or amended for clarity. In line with the suggestion of the reviewer, a new figure have been added. Please see the revised manuscript.

Comments

1)  In section 3.1.3, the symmetry plane condition was used for the side boundary. However, it’s unclear if wave damping was used for that boundary. Besides, the slip wall condition was used for both top and bottom boundaries, this is unusual settings, any specific reason?

• The vessel considered in this study is a relatively high-speed vessel which generates relatively large stern waves. Therefore, a numerical damping zone was applied to ensure no wave reflection at the outlet boundaries. The divergent waves from the stern are not in much contact with the side boundary, which is why the wave damping zone was employed. The slip boundary condition has the same effect as the velocity inlet condition. This study employed the slip wall boundary condition, referring to Lee et al. [12] as follows;

Lee, C. M.; Yu, J. W.; Choi, J. E.; Lee, I. Effect of bow hull forms on the resistance performance in calm water and waves for 66k DWT bulk carrier. Int J Naval Arch. Ocean Engng. 2019, 11, pp. 723–735.

 

2) In section 3.1.4, images demonstrating the CFD mesh from different perspectives are needed.

• Figure 3, showing the image of mesh system, has been newly added in the revised manuscript. (Line 169, 172)

 

3)  In section 3.2, the authors should elaborate what the subscripts M and S represent.

• The sentence “Here, the subscript S and M refer to the ship and model scale, respectively.” has been added at the end of the 1^st paragraph of section 3.2 (Line 178, 179).

 

4)  A verification study is missing, which makes it hard to estimate the uncertainties, especially when the resistance reduction is only 2.36%.

• In line with the reviewer’s suggestion, a grid dependence test was carried out for the initial hull with three different grids. Considering the results and computation time of numerical simulation, medium mesh is selected as the basic grid system. (Table 2, Line 204)

 

5) Section 4.1, how ? is determined? According to what criteria? Since there are two design variables, shouldn't the design matrix being two-dimensional? But only Δ?? is explored here.

• is independent variable and ? is dependent variable. In order to satisfy the displacement constraint,  has been adjusted for each   (Line 216)

 

6) From Fig. 9, it’s seen that if the stern flap was used, the resistance reduction is very small, but the original form has lower trim angle. Will it make the original actually a better design?

• No, the authors would like to differ. Compared to the initial hull with flap, the optimal hull with still has the lower ressitance. Even though the original hull with flap shows smaller trim angle, the slight reduction in the trim angle does not make the original hull preferrable to the optimal hull. This is because the trim angle is not the cost function to be minimized.

 

7) Line 276, the amplification of bow waves is not obvious from the wave pattern, should extract some wave profiles to elaborate this.

• This is true for the overhead wave elevation shown in the left in Fig. 11. In the wave profiles shown in the right, however, the amplification of the bow waves due to the stern flap is obvious. We seek the understanding of the reviewer on this.

 

8) Line 270 and Line 278, “didn’t” should be “did not”, “can’t” should be “cannot”. Similar mistakes should be avoided elsewhere.

• These have been corrected accordingly (Lines 283 and 290).

 

We feel that the comments of the reviewer were stimulating and productive. These led to substantial improvements in the revised paper. We are appreciative of the reviewer for our paper.

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

The paper describes an analysis of hull lines (hull shape) of a fishing vessel using a CFD method. The hull lines variations studied are parameterized by two parameters, the effect of which on ship resistance is studied (however only the effect of one of these is shown). The optimum seems to be very flat and thus the effect on resistance is at most some percent.

 

The paper is very nice presentation of design of hull lines, but has not much wider interest as the study is focused on a particular ship. The presentation is clear and shows logically the reasoning leading to results. The CFD method used could have been described a bit more, now just the main features of the method are mentioned. This could be improved a bit.

Author Response

Response to Reviewer 2

 

Manuscript ID: applsci-1271997

Type of manuscript: Article

Title: An optimization study on the hull form and stern appendage for improving resistance performance of a coastal fishing vessel

Authors: Jin-Won Yu, Min Kyung Lee, Yang-Ik Kim, Sung-Bu Suh, Inwon Lee*

The paper describes an analysis of hull lines (hull shape) of a fishing vessel using a CFD method. The hull lines variations studied are parameterized by two parameters, the effect of which on ship resistance is studied (however only the effect of one of these is shown). The optimum seems to be very flat and thus the effect on resistance is at most some percent.

The paper is very nice presentation of design of hull lines, but has not much wider interest as the study is focused on a particular ship. The presentation is clear and shows logically the reasoning leading to results. The CFD method used could have been described a bit more, now just the main features of the method are mentioned. This could be improved a bit.

• We are thankful to the reviewer for the generally positive and constructive comments. In preparing for the revised manuscript, we have attempted to incorporate faithfully the suggestions of reviewer. Several sentences, marked red, have been either inserted or amended for clarity. In particular, the boundary conditions have been described in more detail and the results from the grid dependence tests have been added. In line with the suggestion of other reviewer, a new figure have been added. Please see the revised manuscript.

We feel that the comments of the reviewer were stimulating and productive. These led to substantial improvements in the revised paper. We are appreciative of the reviewer for our paper.

 

Author Response File: Author Response.docx

Reviewer 3 Report

This manuscript discusses various design parameters of a coastal fishing vessel hull to minimise the wave-making resistance. The authors start from a real hull design and modify the chine breadth in the fore body, achieving an optimum value by which a maximum resistance reduction of 2.36% is reached. However, this optimum value results in a high trim angle which affects the safety of the vessel due to the lack of forward visibility. Therefore, the design of a stern flap is also evaluated in order to reduce the trim angle without affecting the resistance improvement obtained by modifying the chine breadth. The analysis of the different hull models is performed by means of a viscous flow solver based on the Reynolds-averaged two-phase Navier-Stokes equations.

The subject of this research work fits in with the thematic of the open access journal Applied Sciences and the results of this research work are potentially useful and highly interesting for its publication in Applied Sciences. On the other hand, I have not found any notable issues that should be reviewed to improve the work of the authors of this manuscript. Other design parameters could be studied and other evaluation criteria could be considered. However, the study, although somewhat limited, is clearly and successfully addressed from the introduction to the conclusions. The motivation for the manuscript and the discussion of previous work in the introduction is appropriate. The simulation setup is sufficiently detailed for this kind of work. The authors also provide a validation of this configuration by comparing with experimental results. The results are appropriately discussed and the conclusions summarise the main goals successfully achieved.

Therefore, taking into account all of the above, my suggestion is Publication without changes.

Author Response

Response to Reviewer 3

 

Manuscript ID: applsci-1271997

Type of manuscript: Article

Title: An optimization study on the hull form and stern appendage for improving resistance performance of a coastal fishing vessel

Authors: Jin-Won Yu, Min Kyung Lee, Yang-Ik Kim, Sung-Bu Suh, Inwon Lee*

This manuscript discusses various design parameters of a coastal fishing vessel hull to minimise the wave-making resistance. The authors start from a real hull design and modify the chine breadth in the fore body, achieving an optimum value by which a maximum resistance reduction of 2.36% is reached. However, this optimum value results in a high trim angle which affects the safety of the vessel due to the lack of forward visibility. Therefore, the design of a stern flap is also evaluated in order to reduce the trim angle without affecting the resistance improvement obtained by modifying the chine breadth. The analysis of the different hull models is performed by means of a viscous flow solver based on the Reynolds-averaged two-phase Navier-Stokes equations.

The subject of this research work fits in with the thematic of the open access journal Applied Sciences and the results of this research work are potentially useful and highly interesting for its publication in Applied Sciences. On the other hand, I have not found any notable issues that should be reviewed to improve the work of the authors of this manuscript. Other design parameters could be studied and other evaluation criteria could be considered. However, the study, although somewhat limited, is clearly and successfully addressed from the introduction to the conclusions. The motivation for the manuscript and the discussion of previous work in the introduction is appropriate. The simulation setup is sufficiently detailed for this kind of work. The authors also provide a validation of this configuration by comparing with experimental results. The results are appropriately discussed and the conclusions summarise the main goals successfully achieved.

Therefore, taking into account all of the above, my suggestion is Publication without changes.

• We are thankful to the reviewer for the positive comments. In preparing for the revised manuscript, we have attempted to incorporate faithfully the suggestions of other reviewers. Several sentences, marked red, have been either inserted or amended for clarity. In line with the suggestion of other reviewer, a new figure have been added. Please see the revised manuscript.