Experimental Characterization of the Hydraulic Jump Profile and Velocity Distribution in a Stilling Basin Physical Model

Round 1

Reviewer 1 Report

Manuscript: # 821241-peer-review-v1

Title: Experimental Characterization of the Hydraulic Jump Profile and Velocity Distribution in a Stilling Basin Physical Model

Authors: Juan Francisco Macián-Pérez, Francisco José Vallés-Morán , Santiago Sánchez-Gómez, Marco De-Rossi-Estrada  and Rafael García-Bartual

 

Authors present experimental results to characterize hydraulic jumps in stilling basins. This topic is relevant and of interest to Water readers.

By reading this work carefully, I find that the manuscript suffers from a large number of shortcomings and deficiencies: i) the paper only presents one experimental configuration with high degree of uncertainty, which strongly influence the credibility of the achieved results, ii) The presentation of the paper is very confused and sometimes hard to read, iii) the results and discussion suffer from many weaknesses, iv) the work does not present any innovative aspects!

This manuscript needs deep improvements before resubmitting it to revision. I think, unfortunately, that this manuscript is not suitable for publication in its present form.

 

Some comments

Abstract:

The abstract requires improvement. You must describe your research objectives clearly and simply.

 

2.1. Physical Model Design

- You said, “In the design process of the physical model, choosing a general and representative case study was prioritized. In these terms, a typified USBR II stilling basin was the analyzed energy dissipation structure.” These sentences are very hard to understand, could you please rewrite them in a simpler way?

- In Table, the design Parameters are not defined!

- You said, “In order to avoid significant scale effects in the model, the limiting criteria established by Heller [22] were considered”, Would you briefly indicate the criteria;

- Why did you choose a value of 99 for the Weber number over a suggested minimum of 110? Could you please elaborate on this?

- “The design of the physical model finally developed resulted from the balanced consideration of three key aspects … The resulting physical model was a compromise solution among these mentioned factors.” This paragraph summarizes neither the purpose of the study nor the novelty of the study!

I think this section lacks a definition sketch (axial section) of the hydraulic jump in the stilling basin.

  2.2. Experimental Device

-You said, “In terms of the pumping system, the inlet was made through a pressure flow, with a transition to free surface flow right before the entrance of the sloping channel.” What do you mean by “through a pressure flow”? this is not clear to me!

- Figure 2: Is it useful to set up the three similar images? I think one is sufficient;

2.3. Instrumentation

2.3.1. Time-of-flight Camera

- The quality of the free-surface measurements, using a Time-of-flight Camera, is strongly influenced by the aeration intensity of the hydraulic jump; how was uncertainty assessed in this case? Taking into consideration that the bubble concentration significantly decreases moving downstream of the hydraulic jump.

- Figure 3: What are the cloud/band sizes shown in this figure?

 

3. Results and Discussion

- How did you experimentally get y1? 

- In Table 2: the precision of the experimental value 12.00 of y2/y1 seems strange to me, how did you get it?

- You said: “Table 2 shows …, the affection of the energy dissipation devices to the flow is significant.” How did you observe the significant effect of energy dissipation devices from Table 2? This point should be elaborated more;

- The duplication of the axial profiles shown in Figure 5 is unclear to me! The experimental profiles must be represented in class scatter mode;

- You said: “As observed in Figure 5 for the lowest  x values,” what do you mean by lowest x values?

- You said: “Moreover, for ~ 0.7 m and for > 2 m, the structure of the channel interfered with the measures.” why and how?

- Figure 6. Dimensionless free surface profile of the hydraulic jump obtained from the numerical model and comparison with bibliographic information [5,8,9]. Numerical model! You mean physical model, is not it? profiles must be represented in class scatter mode. The same form of authors’ citation should be used in the figures and in the text, such as Bakhmeteff & Matzke [9];

You said: “As it can be observed in Figure 6, such higher flow depths basically remain along the central part of the roller, up to ~ 0.9. Thus, the subcritical flow depth was reached in the stilling basin physical model closer to the hydraulic jump toe, when compared to the CHJ.” What do you mean by this observation? In Bakhmeteff & Matzke [9], it remains up to X » 1.5, how to explain this?

- You said: “As shown in Figure 6, certain differences in non-dimensional depths are found between both experimental investigations.” Please specify which both experimental investigations!

- You said: “This behavior is…On the one hand, the intense aeration characteristic of the hydraulic jump phenomenon leads to bubbles and droplets being continuously expelled. This causes changes of light intensity that introduce bias in the image treatment.” The discussion of results in this paragraph is very qualitative; the lack of quantitative analysis weakens the credibility of results.

- You said “These structures must adapt to new scenarios posed by climate change and still guarantee the fulfillment of their energy dissipation purpose.” How? Please explain this;

3.3. Hydraulic Jump Roller Length

You said: “This is in good agreement with the results presented in Figure 6 regarding the free surface profile of the hydraulic jump in the basin, which reached the subcritical depth faster than the CHJ.”

3.4. Velocity Distribution

- You said: “In addition, several tests conducted in the experimental channel, with the Pitot tube placed in a reverse position, showed that this device was not able to capture backwards velocities in the flow.” Without the backwards velocities, how did you define the stagnation point to estimate the hydraulic jump roller length?

- The horizontal component of the freestream velocity must be clearly defined;

- Since the uncertainty of the flow velocity within the hydraulic jump is considerable, due to the high bubble concentration, I suggest you to add the uncertainties bar of the measured velocities in Figure 9.

- You said: “As observed during the experimental campaign, the explanation arises from the effect of the chute blocks at the beginning of the basin. The deflection caused by these energy dissipation devices triggers the flow in the region closer to the channel streambed and hence, the maximum velocities are achieved in the lowest part of the vertical profile”, this is unclear to me, could you elaborate it better?

- This section needs deep improvements; the results are superficially presented and discussed.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Review of the manuscript "Experimental Characterization of the Hydraulic Jump Profile and Velocity Distribution in a Stilling Basin Physical Model" by Juan Francisco Macián-Pérez et al.

The manuscript is well written, as the aims of the work are well structured. A minor revision of English must be conducted on some parts of the text. In any case, I would like to provide just some elements that can be improved before publication.

Suggestions/reccomandations  

- I invite the Authors to present in the graphs and also in the comments a discussion on the propagation of errors. No error bar is presented (see for example figs 6, 7, 8, 9, 10). This would favor a quantitative interpretation of the errors of the measurements made also in consideration of the LiDAR methodology proposed here.   - The authors must better highlight, in the discussions and conclusions, the aspects relating to the hydraulic measurements performed compared to other potential measurements (for example PIV or LDV laser measurements) that can be carried out in the same conditions. Is this methodology proposed here more convenient? and if so why?   The overall evaluation of the manuscript is satisfactory. Therefore, from my point of view, I consider this work susceptible of publication on Water after performing this minor revisions.  

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors provide very detailed responses to my comments, and in each case they have satisfied my question. I think the changes they have made significantly improve the paper. I think that this revised paper is suitable for publication after undergoing some minor revisions.

Minor revision

• Introduction: It would be better if the authors can provide more details about the concept of the hydraulic jump classification (transition between undular and classical jumps as presented in these previous studies:

Ohtsu I., Yasuda Y., Gotoh H. (1997). Discussion of Characteristics of undular hydraulic jumps: experimental apparatus and flow patterns by Chanson H and Montes JS (Paper 7859). J. Hydraul. Eng., 123(2):161-164

Ohtsu I, Yasuda Y, Gotoh H (2001). Hydraulic condition for undular-jump formations. J Hydraul Res 39(2):203–209 12.

OhtsuI, YasudaY, GotohH (2003) Flow conditions of undular hydraulic jumps in horizontal rectangular channels. J Hydraul Eng 129(12):948–955.

• Table 1: The definition of the Parameters can be found in Figure 1. Yes, but only indicated in Figure 1, I think it is better to define them in the title of Figure 1, i.e., LII is the…, d1 is the…and so on;
• Please indicate (qualitatively) in the sketch of the hydraulic jump in Figure1b the different jump characteristic parameters such as, Lr, x0, y1,…, and the coordinate system;
• In Figure 3b the hydraulic jump (upstream) shows a sort of trapezoidal shape, this is due, according to previous studies by Ben Meftah et al. (2010, 2008), to an oblique shock-wave formation. What do you think about this, taking into account that spillways are generally very large? Please consider these references:

Ben Meftah M., Mossa M., Pollio, A. (2010). Considerations on shock wave/boundary layer interaction in undular hydraulic jumps in horizontal channels with a very high aspect ratio. European Journal of Mechanics - B/Fluids, 29, 415-429.

Ben Meftah M., De Serio F., Mossa M., Pollio A. (2008). Experimental study of recirculating flows generated by lateral shock waves in very large channels. Environmental Fluid Mechanics, 8, 215-238.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf