Research on Maneuverability Prediction of Double Waterjet Propulsion High Speed Planing Craft

Round 1

Reviewer 1 Report

The paper addresses a novel area that is of concern to researchers and boat designers. Being able to predict maneuvering of high-speed boats before sea-trials would be of great value. The authors present a reasonable approach to this challenge, but the validation is incomplete. Suggestions for improvement are following:

1. In section 2, on page 4, lines 123-127, the authors refer to the boundary entrance as 1.5 times that length of the bow and the boundary exit as 3.5 times the length of the stern. However, the bow and the stern are positions on the hull and have no inherent length associated with them. What parts of the hull are these references actually about?

2. What is the Froude number (actually, Froude numbers for all the speeds) of the vessel in this report? Froude number is the best way for a reader to understand what speed regime the boat is traveling in (pre-planing, fully planing, etc.). For example, in table 2 - what is the Froude number associated with a speed of 1.513 m/s, in table 4 the speeds are 2.33 m/s and 2.91 m/s, and in table 6 the speeds range from 1.38 m/s to 10.59 m/s. Please provide relevant Froude numbers associated with these speeds.

3. In table 4, I believe the authors mean for the first 4 rows to be Pure Sway (not Pure Wanton), the next 4 rows to be Pure Yaw (not Pure Bow), and the final 4 rows to be Yaw with drift angle (not Bow with drift angle). The text seems clear on what tests were simulated, but the table is very confusing.

4. In table 4, the Pure Bow (should be Pure Yaw) amplitudes are listed as 0.1, 0.2, 0.3, and 0.4 meters. How is angle measured in meters?

5. In Figure 5, the captions should be corrected to read Pure Sway, Pure Yaw, and Yaw with drift angle. Also, the figures are small and hard to read the numbers in the images.

6. In Figure 5, each image as a t = ##T. But this is never explained. What is it referring to?

7. The sea maneuverability tests that were compared with the predicted motions were conducted at 2.33 m/s and 2.91 m/s forward speed. But the simulations that determined the hydrodynamic derivatives were conducted at a forward speed of 1.513 m/s. Generally, it is assumed that the hydrodynamic derivatives depend on forward speed, so I would not expect the simulations to provide the relevant hydrodynamic derivatives for the sea tests. Was there a justification for completing the simulation at a different forward speed? Can you should evidence that this different forward speed does not change the expected hydrodynamic derivatives?

8. The same concern is for the Maneuvering Simulation presented in section 4. Were the same hydrodynamic derivatives as shown in table 3 applied for this condition? At both the 7.7 m/s and 11.92 m/s speeds? These speeds are significantly faster than the 1.513 m/s from table 3, so a stronger justification is needed here. Or were the hydrodynamic derivatives recalculated at the medium and high speeds? If so, please make this clear in the paper.

9. I have lots of questions about figures 8 and 9. In addition to the comments below, I found the plots were discussed in the text but not referred to directly. It would help the reader significantly if the authors would specify which subplot showed the aspects being discussed.

1. Why is figure 8a show the circles as moving to the left with increasing rudder angle but in figure 9a the circles are all starting from about the same point on the x-axis?

2. Please change the label for figures 8b and 9b to be forward speed variation curve. Having the labels different for the two figures adds confusion and what I am looking at in either is not very clear. I assume the drop in forward velocity starts when the rudder is thrown over?

3. Please change the label for figures 8c and 9c to be Sway velocity variation curve. Similar comments to previous statement.

4. For figures 8d and 9d, I am guessing the label should be the ‘Heading angle variation curve.’ Again, having different captions leads to confusion. And, in this case I really don’t understand what I am looking at and the authors don’t even refer to this subplot in the text, so there is no additional context. Please either add commentary on the value of this plot or remove both.

5. Please change the labels of figures 8e and 9e to Yaw velocity curve.

10. I don’t understand what I am looking at in table 6. Perhaps a figure showing the Ad, Tr, DT, and Do would help clarify the measurements presented in the table. It would also be helpful to connect the values in the table with the plots in figures 8 and 9. I am particularly unclear about what the V (m/s) refers to. Is this the forward speed of the vessel as shown in figures 8b and 9b? If forward speed, perhaps referring to it as U (instead of V) would be appropriate.

11. On page 11, lines 228-230, the authors state the maximum rotation diameter reaches 3.4 times the length of the ship for the medium speed condition and 9 times the length of the ship for the high speed condition. Is there a figure where I can see this? Is it just based on 21.32/6.58 = 3.24 55.96/6.58 = 8.59?

12. What is an “anti-transverse distance”? I am not familiar with this terminology.

13. The last sentence under table 6 states that the “rotation is good.” What are the criteria for determining “good rotation?” What are the standards for determining acceptable maneuverability?

14. Where is the turning period given? I see it referenced in the text, but I am not clear where to find the data presented.

15. Please change the plot captions in Figures 10 and 11:

1. figure 10a and 11a - Heading Angle

2. figure 10c and 11c - forward velocity variation curve

3. figure 10d and 11d - sway velocity variation curve

4. figure 10e and 11e - yaw velocity curve

16. In figure 10a and 11a, what does the label refer to? What is the difference between ‘10/10, ?’ and ‘10/10, ?’?

17. The subplots in figures 10 and 11 are never directly referenced in the text. This makes it hard for knowing which is being used as evidence for the claims in the text.

18. How did you determine the exceedance angle? (figure 10e and 11e)

19. Under table 7, the authors state “It can be seen that at the same speed, the speed oscillates with time…” What is the second ‘speed’ referring to if the first part of the sentence says the speed is the same?

20. What is overtime ts referring to?

21. What is the motion period? This is never defined.

22. The authors state “the maneuverability at 20/20 is better than at 10/10.” It doesn’t look that much different to me. Maybe it is better, but without a reference for what is the range, it may be insignificantly better.

23. What does it mean that the “maneuverability of the double water jet propulsion planing boat is more flexible”?

24. A nomenclature table would be very helpful.

Comments for author File: Comments.pdf

Author Response

Please refer to the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

This paper is carry out the prediction of ship maneuvering with the MMG model, and a comparison was made with the ship test. It seems the research gap needs to strengthen with more literature review. There are only 10 references and less than 5 references about the MMG model. The authors should improve the introduction section to enhance what is the difference between the previous studies, and why the authors use MMG rather than others methods. Please see my comments in the attachment file.

Comments for author File: Comments.pdf

Author Response

Please refer to the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thank you for addressing my concerns. I think the paper is noticably improved and the work is easier to understand.