The Effect of a Linear Free Surface Boundary Condition on the Steady-State Wave-Making of Shallowly Submerged Underwater Vehicles

Round 1

Reviewer 1 Report

This paper deals with the investigation of the effects of the linearized free surface boundary conditions on the loads predicted on an underwater vehicle. The means of assessment is by comparing a potential flow  methodology (Rankine-source BEM) with the OpenFOAM CFD solver.

 

Overall the paper is well written and the results are interesting. There are some minor comments that to the reviewers opinion would improve the quality of the manuscript.

·       -The authors should clearly state how the wave resistance is measured in case of the CFD simulation.

·       -  Regading the grid convergence tests in page 9,Figure 4 something is not going as it should. I would expect the resistance to converge with much fewer cells (of the order of 2-5 million cells-even less).

As Figure 5 suggests the mesh is almost uniform anywhere and probably this is why the mesh size increases so much. It is common in the CFD community to make anisotropic grids to gradually coarsen to avoid the number of cells prohibitively increasing.

 I think a comment should be added here, because it will be confusing for the audience of the paper.

·        - In section 3.1 the authors state that neither model considers viscous forces. This should be state clearly earlier.  See my first comment about wave-making resistance.

·        - In section 3.4, do you employ the standard SST or with the Devolder modification? Is there overproduction of turbulence near the free surface?

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

this article dealt with two codes for submerged underwater vehicle. The limitation of the free surface boundary condition and viscosity was discussed in BEM code. 

The authors compared the results from CFD and BEM. But there were no validation results of CFD and BEM, respectively. The authors must to add the validation results for a similar underwater vehicle.  

In RANSE CFD, kOmegaSST model was used. How about the Reynolds number. The turbulence model was proper in this simulations. How to consider the turbulent kinetic energy in BEM?

For the wave pattern as shown in Figures 9 and 10, the results by RANSE CFD and BEM were different. Which one is proper?

In Figure 19, there are some CFD-viscous results for h/d=1, 2, 3. However, there are no CFD-viscous results for h/d=0.5

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The manuscript was revised.