Numerical Research on the Resistance Reduction of Air Intake
Round 1
Reviewer 1 Report
Authors write "During simulation, the govern equation of incompressible viscous flow is described by the Reynold–Averaged Navier–Stokes Equations (RANSE) and continuity equation. To close this set of equations, the Shear Stress Transport (SST) turbulence model is used. The volume of fluid (VOF) model is applied to track the location and evolution of the free surface".
I suggest authors to describe to include above equations and resolution methods used
Author Response
I suggest authors to describe to include above equations and resolution methods used.
Thanks for your review carefully, the RANSE equation and SST turbulence model, VOF have been added, please refer to the new revison.
Reviewer 2 Report
The previous version of the manuscript, submitted to Water some time ago, was characterized by many lacks. The present version is improved, with the authors following many of my suggestions and solving some of the issues.
However, English-use problems still exist (only some of the problems follow: L51: “CALM water”; L97: “the simulation is CARRIED OUT”; L127-128: “mesh size … increaseS”; L132: “has DIRECT influence”; L135: “resistance … IS”; L139: to be reworded; L176: “FRICTION resistance”).
I (again) suggest the authors to carefully check the manuscript, also with the help of either a native English speaker or a specialized language service.
Further, some reference numbers between L24 and L54 should be improved, i.e. using appropriate spacing and square brackets.
At L92, the meaning of the term “I” should be provided.
A brief description of CFX should be included (L97), e.g. solver type, numerical scheme.
The caption of fig.8 should clearly indicate which is the model with/without air intake.
As already suggested, figs. 8 and 13 should include x-y axes, to properly understand the geometry and size of the discussed model changes.
As already suggested, figs.12 and 15 should be improved with the addition of x-y axes. Symbols (e.g., arrows, circles) should also be included to properly highlight regions where the most important changes occur.
Fig.15 should be split into three separate figures, one per Froude number. Then, due to the importance of such results, discussion of fig.15 needs to be significantly improved, e.g. highlighting differences among the proposed models and improvements of one over the others at the different flow regimes.
Author Response
The previous version of the manuscript, submitted to Water some time ago, was characterized by many lacks. The present version is improved, with the authors following many of my suggestions and solving some of the issues.
Firstly at all, Thanks for your careful and precise review about this essay, and hope the poor writing skill does not bother you.
However, English-use problems still exist (only some of the problems follow: L51: “CALM water”; L97: “the simulation is CARRIED OUT”; L127-128: “mesh size … increaseS”; L132: “has DIRECT influence”; L135: “resistance … IS”; L139: to be reworded; L176: “FRICTION resistance”).
The English use problems mentioned above have been correceted.
Further, some reference numbers between L24 and L54 should be improved, i.e. using appropriate spacing and square brackets.
The reference number have been remodified, especially 5.
At L92, the meaning of the term “I” should be provided.
The I means the unit vector of the pressure, and added in the paper.
A brief description of CFX should be included (L97), e.g. solver type, numerical scheme.
ANSYS-CFX is one of the most widely used CFD software at present. It discretizes the govern equations by the finite volume method, and integrates each grid in the domain by solving the differential equations, thus the discrete algebraic equation is obtained and used in solution.
And also added the above description in the paper.
The caption of fig.8 should clearly indicate which is the model with/without air intake.
As already suggested, figs. 8 and 13 should include x-y axes, to properly understand the geometry and size of the discussed model changes.
As already suggested, figs.12 and 15 should be improved with the addition of x-y axes. Symbols (e.g., arrows, circles) should also be included to properly highlight regions where the most important changes occur.
Fig.15 should be split into three separate figures, one per Froude number. Then, due to the importance of such results, discussion of fig.15 needs to be significantly improved, e.g. highlighting differences among the proposed models and improvements of one over the others at the different flow regimes.
I remark the Fig.8 & 13 with X, Y axes, and make it clear with different models. The Fig.15 also divided into 3 parts. Also discussions and descriptions added below the figures. Please refer to the revision.
Reviewer 3 Report
The manuscript's main objective is to study the drag-reducing effect of air intake in planning trimarans. Specifically, the authors compare four different trimaran designs, one with no air intake, and three with an air intake of different dimensions. The simulations are computed with Ansys CFX. A discussion of the results concludes that the air intake improves the drag-reducing effect, and that depending on the Froude number the size of the intake can generate more or less resistance.
The topic of the manuscript is within the aim of Water-MDPI, and the discussion is of high interest to the readers of Water-MDPI. Therefore, after minor corrections, the paper can be published in Water-MDPI.
Regarding English, the manuscript can benefit from a careful proofread for both the typos and the typesetting.
Comments:
- In the second paragraph of the introduction, some numbers look randomly spread throughout the text. (e.g.: line 37 "... pool. 5With ...")
- Line 81: What's the volume of fluid model? Could you add any reference?
- Line 87: Why 6-DOF? Would be 9-DOF better? Why is 3-DOF not enough?
- Line 97: Specify ANSYS CFX.
- Are you the authors of Fig. 11?
- Comparisons are hard in Fig. 15, I'd suggest another presentation to make differences easier to grasp.
Author Response
First at all, appreciate for your recognition and review about this essay.
Comments:
- In the second paragraph of the introduction, some numbers look randomly spread throughout the text. (e.g.: line 37 "... pool. 5With ...")
The reference numbers have been remodified again.
- Line 81: What's the volume of fluid model? Could you add any reference?
The basic idea of the VOF method is to define the marking function α in the discrete domain, and to determine the value of the volume function in one grid according to the volume of the fluid in it: When the value of α is 1 or 0, there is only one fluid in the grid. When the value of α is between 0 and 1, it is occupied by two kinds of fluids, that means there is a free surface in the grid.
The above descriptions also added in the paper.
- Line 87: Why 6-DOF? Would be 9-DOF better? Why is 3-DOF not enough?
The 6-DOF in this paper means the movements and rotations in x, y, z axes, they are sway, surge and heave; roll, pitch and yaw. In cosidering of the completeness during ship movments, the manoeurving and seakeeping control equations are based on the 6-DOF. And in this essay, in order to simulate the ship straight ahead motion, the movement and rotation of y axe is fixed.
- Line 97: Specify ANSYS CFX.
ANSYS-CFX is one of the most widely used CFD software at present. It discretizes the govern equations by the finite volume method, and integrates each grid in the domain by solving the differential equations, thus the discrete algebraic equation is obtained and used in solution.
And also added the above description in the paper.
- Are you the authors of Fig. 11?
Yes.
- Comparisons are hard in Fig. 15, I'd suggest another presentation to make differences easier to grasp.
The Fig.15 also divided into 3 parts. Also discussions and descriptions added below the figures. Please refer to the revision.
Round 2
Reviewer 2 Report
The revised manuscript has been improved by the authors, though some concepts of my previous reviews have not been caught.
In particular, I suggested them to carefully check the manuscript (not only the few points I highlighted), also with the help of either a native English speaker or a specialized language service. Such comment has not been considered by the authors, who are, once again, strongly suggested to revise their manuscript under this point of view.
Further, the first part of the introduction section is chaotic, with track changes still there. This makes the reading quite hard. In addition, the suggested improvement has not been implemented, i.e. proper use of spacing and brackets to report references (e.g., [1]).
In figures 16 and 17, the color bar should be included, as for fig.15.
Author Response
Thanks for your review, frankly.
In particular, I suggested them to carefully check the manuscript (not only the few points I highlighted), also with the help of either a native English speaker or a specialized language service. Such comment has not been considered by the authors, who are, once again, strongly suggested to revise their manuscript under this point of view.
Due to this is 1st time write this manuscript with English, and feel sorry again for trouble you because of the poor English, I revise the manuscript with my colleague again. And the essay is modified by American Journal Experts before, however, it seems not benefited. If you have any ideas I would like to.
Further, the first part of the introduction section is chaotic, with track changes still there. This makes the reading quite hard. In addition, the suggested improvement has not been implemented, i.e. proper use of spacing and brackets to report references (e.g., [1]).
About the references I think it's incompatible word vision, I try print it in PDF type and I found the problems you metioned, and I re-corrected them and re-print it, it is ok now. And the track change is kept as the requirments from editor, and to ensure your reading qulity, I attached a revison without track change, please refer to.
In figures 16 and 17, the color bar should be included, as for fig.15.
Added as you metioned.
Author Response File: 
Author Response.docx
Reviewer 3 Report
Dear authors,
Thank you for the revision of the manuscript. Although the manuscript has been improved, there are still some points to remark.
The references in the introduction are messy, some are just numbers, others around brackets. Please, follow the guides in the Water-MDPI "instructions for authors" https://www.mdpi.com/journal/water/instructions#references
Line 122: Thanks for the clarification of "the volume of fluids method (VOF)". Could you add a reference.
Line 145: Specify ANSYS-CFX.
Line 181-186. Could you please indicate the order of the elements? Are there linear, 2nd order, higher order?
As stated in the previous review, the manuscript can benefit from a careful proofread for both the typos and the typesetting.
Author Response
Thanks for your review, frankly.
The references in the introduction are messy, some are just numbers, others around brackets. Please, follow the guides in the Water-MDPI "instructions for authors" https://www.mdpi.com/journal/water/instructions#references
About the references I think it's incompatible word vision, I try print it in PDF type and I found the problems you metioned, and I re-corrected them and re-print it, it is ok now.
Line 122: Thanks for the clarification of "the volume of fluids method (VOF)". Could you add a reference.
Added a reference in 16.
Line 145: Specify ANSYS-CFX.
Added.
Line 181-186. Could you please indicate the order of the elements? Are there linear, 2nd order, higher order?
I found that Line 181-186 is the description of equation and the abbreviations, and the data comparision. It's not clear for the question, please confirm it, thanks.
