Electrical Swath Ships with Underwater Hulls Preventing the Boundary Layer Separation

Round 1

Reviewer 1 Report

1. What does mean "unseparated" at thr title? Single hull? Absence of flow separation? Absence of turbulent boundary layer? More clear definition is needed.
2. The authors show the maximal limit of laminar layer, see line 115: Re <1.4*10⁶. Unfortunately, there are nothing practical demonstrations of laminar layer existence at much bigger relative speeds. But, for example, Reynolds number of the shown yacht is 1.86*10⁸.
3. The initial assumptions, which were used fro the yacht designing, are not correct: - energy loss for flow pattern is not estimated; - small friction drag is not demonstrated; - wave resistance is absent only at much bigger immersions (about length of a hull); - high seakeeping of SWATH is well known fact. 
4. Really, if model test results and assumption on turbulent boundary layer are applied, the hydrodynamic quality 1/k is about 70, but not 165, as the authors claim. Please see the book "Ships with small water-plane area", Backbone Publ. Co., Isbn-13978-09742019-3-1, Hoboken, USA, 2007.
5. So idealized image on the possibility of turbulent boundary layer elimination will insert the reader to error referring the real situation.  

Author Response

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Reviewer 2 Report

- The title contains electrical, but the paper does not cover electrical aspects at all

 

- Unseparated hulls is not very clear. SWATH terminology considers Lower Hulls and Strut. I think authors refer to Single Lower Hulls, in contrary to Tandem Lower Hulls.

 

- The paper needs an urgent language review: what is neutral buoyant?

 

- Reference [7] repeated several times, is wrong in the bibliography

 

- References 9 and 10, and much others, refer to books. Cite the chapter and pages where you refer.

 

- Line 63, the attached flow pattern was achieved only the use of... is not clear at all

 

- Consider to cite recent references such as (A parametric methodology for the preliminary design of SWATH hulls, F.Pérez-Arribas, J.Calderon-Sanchez. Ocean Engineering 197. 2020) and classical ones (Lamb, G. R. (1988, October). Relationship between seakeeping requirements and swath ship geometry. In OCEANS'88.'A Partnership of Marine Interests'. Proceedings (pp. 1131-1143). IEEE.)

 

- In Figure 2, try to add the graphical description (as in Figure 1) of the Albacore, Blue Shark and Sailfish.

 

- In Figure 2, why the red curve does not finish at a 0 radius as the others? It is not closed.

 

- In 101, gives the description of CV. Is this CV equal to the one of line 134?

 

- In 103, writes Hoerner formula to compare both expressions please.

 

- In 116, you refer to (4) but this I think it is not correct, since (4) is a Fn number

 

- From 143 to 160, authors refer to airplanes... is out of the scope

 

- 172 this is the ship hull speed Froude number? (before dynamic planing start)

 

- In 173, kw is the propulsion propulsive efficiency?

 

- Section 5 has a different format

 

- The examples in Fig 5 and Fig 6 do not show the draft (still water surface)

 

- These examples are not realistic at all: they are not constructible from the structural point of view. You have to work more on them.

Author Response

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Round 2

Reviewer 1 Report

1. The text contains the assumption on laminar boundary layer at full length. Than, it must be included into the title.
2. Yes, my reference contains a mistake of Reynolds number of the examined yacht, really Re = 7 * 10⁷. But the correct value is much bigger, than the noted by authors limit 1.4*10⁷. It means, the existence of laminar boundary layer is not established now. Moreover, the laminar boundary  layer on the sea animals is ensured not only the hull shape, but by the type of surface, which can`t be realized on ship hulls today.
3. If the existence of laminar layer on full length is not established now, you can describe the ideal image of the yacht with big "IF" before only.
4. The authors "do not discuss" the value of wave resistance, but use an assumption on its elimination to the power estimation...It is straight false of the calculations.
5. The paper can be published, if  the word IF will be included at all assumptions before estimations of the yacht resistance. It can be examined as an ideal level of the vessel resistance, the possibility of it is not established today. 

Author Response

1. Please see the attachments

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Reviewer 2 Report

The paper has been improved in the revised form. I agree that journal dates do not allows great changes.

Author Response

Thanks for your review

Round 3

Reviewer 1 Report

1. The title was corrected, but the text contains, as previously, a lot of  word "unseparated".
2. The dependence of viscosity resistance of sea animal from the characteristics of their surfaces is not examined. The resistance depends not only from the body shape. The influence of surface type must be examined too.
3. Flow separation is not the transition of laminar boundary layer to turbulent one. It is two various characteristics of a flow. Separation of the laminar layer is possible too, and it means a very sufficient growth of resistance.
4. And what does it mean, "neutrally buoyant" vehicle? Any body, which have the weight corresponds to volume exactly, is neutrally buoyant one...
5. Referring to the paper content, it can be named as "Electrical SWATH ship with ideal towing resistance". 

Author Response

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