Application of Vortex Identification Methods in Vertical Slit Fishways
Round 1
Reviewer 1 Report
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Comments for author File: 
Comments.pdf
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Author Response
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Reviewer 2 Report
Thank the authors for the interesting research work. The reviewer has the following comments and questions:
Line 20, actually "volume of fluid" is not only simulate the multi-phase “interface” but also the flow field of different phases. And I guess your multi-phase interface is the free surface or water surface. Saying multi-phase interface is a bit confusing. Don’t know how many phases you have here.
Line 20-21: “The independence of the grid is assessed”. Your grid independence means in Line 189-195 and Figure 3 talking about Qv lower or greater 0.75, right? But to me, blue in mesh1 and mesh2 is very small. Most of area of mesh1 to 4 is larger than 0.75. Their colors basically are green, yellow and red. Also, normally the grid independence means: as grid number increases, some value converges, or becomes constant, or difference becomes smaller. What is the convergence in Figure 3? I only see a Qv distribution in mesh4. Qv is still changing in different location.
Line 36: what are the main organisms in the ecosystem?
Line 57: “… using the mean Reynolds number (RNG), …”: Do you mean “mean Reynolds number” = RNG. What RNG stands for?
Line 76-77: “… are insensitive to thresholds and can be applied to different cases …”: I can’t understand what the “thresholds” or “different cases” are? Please provide more explanations.
Line 90: “… compared RNG, LES, and the k-ε, k-ω…”: Is RNG a kind of k-ε model?
Line 121: “… the velocity measurements were recorded for more than 3 min …”: What is the meaning and importance of the 3min? What is wrong if recording shorter than 3min? So, how long is your simulation time? Also longer than 3min?
Section 2.2: So, what is your CFD code? Is it a commercial software or in-house code? Reference in detail. If it is a commercial software, you probably need to list its manual to explain its setup. If it is an in-house code, you should provide the detailed development about your algorithm and numerical method.
Equation (4): So how it is solved with Eq. (1) and (2) together. There is no αw in Eq (1) and (2). You have more variables than equations.
Line 167: “… and the viscous bottom layer near the wall was treated using the wall function method. …”: So how much is your y+ for mesh1, mesh2, mesh3 and mesh4? Since you are doing LES, is its grid size small in order to capture the eddies. Why do you need wall function?
Table1: Don’t understand the column for plots.
Line 184-185: “… sufficient for most engineering applications at high Reynolds numbers. …” So, what is your definition of Reynolds numbers? How much is your Reynolds numbers? What much is so-called high Reynolds number in your problem (vertical slit fishways)? Any reference?
Line 189: there is no Equation (10).
Line 203-204: “… The numerical simulation results were found to be in good agreement with the experimental data. …” No. I only see the numerical simulation results and experimental data share the similar trend. Please quantify the “good agreement”, e.g., discussion about the error and analyze the reason.
Line 211-212: “… overall agreement with acceptable accuracy (as shown in Fig. 4(b)–4(d)).”: How accurate do you mean? How much is accurate to you? Please discuss it in quantity. In fact, to me, in 4(b) y/H~0.3 and 0.45 is not so accurate. Both are much lower and deviated from the experimental data a lot. Any explanation?
About “Section 3. Results”: we all know LES can resolve the eddies/turbulence but sometimes the prediction of vortex strength is too stronger. Could you explain how to know if your LES results provide the eddies/turbulence/vortex close to real flow field.
The same question for the three vortex identification methods: Q criterion, Ω method, and Liutex method. So, how to know which one can represent real flow field situation? Your discussion is about which one can capture the flow field information and 3D vortex structures. But it seems we don’t know which one agrees with the real flow field more.
Author Response
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Reviewer 3 Report
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
This paper is very good!
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Thanks the authors for their great effort for revising the paper and responding to the reviewer in detail. However, there are still some flaws. Please check as below.
Line 57: No. Reynolds Average Navier–Stokes=RANS. RNG normally means RNG k-epsilon model but I am not sure what was really used in Ahmadi et al. [14]. So, please check their work. RNG=Re-Normalisation Group. RNG k-epsilon model was developed by Yakhot et al. (1992)
Yakhot, V., Orszag, S.A., Thangam, S., Gatski, T.B. & Speziale, C.G. (1992), "Development of turbulence models for shear flows by a double expansion technique", Physics of Fluids A, Vol. 4, No. 7, pp1510-1520.
Line 93: I know the “free surface” and “water surface” but not sure if people use “free water surface”. Please check.
Line 129: “second-order headwind”: I think normally we say “upwind” method. Please check, especially FLUENT manual.
Line 129: “the time term discretization uses the second order implicit”: Is it should be “the time term discretization is second order implicit”?
Line 130: “The Navier-Stokes under the transient state …”: Probably you should write as “The Navier-Stokes equations under the transient state …”
Line 220: “… and the rigid assumptions employed in the simulation. …” So, which part in your experiment is NOT rigid? Which part in your simulation is rigid? Because I only see the walls in both your simulation and experiment.
Line 251-254: “… (Z＜0.2m) …(Near z=0.2m) …”: Is “Z” the same with “z”? If so, the author should only use one symbol.
Author Response
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Author Response File: 
Author Response.docx
Reviewer 3 Report
The authors have made good corrections. But some symbols are too large and should be adjusted for publication.
The English is okay.
Author Response
Thank you for your suggestion, we have adjusted the size of the symbols in the manuscript.
