Granular Flow–Obstacle Interaction and Granular Dam Break Using the S-H Model with the TVD-MacCormack Scheme

Round 1

Reviewer 1 Report

The subject of the paper is interesting. But some major correction must be done by the authors as follows:

1. Novelty of the paper must be highlighted in Abstract.
2. The results mentioned in Abstract such as "Dam break simulation results also indicate that boundary conditions (whether open or closed) influence the collapse process of the granular pile out of the breach."  are really general. The authors must explain the results exactly.
3. The methodology used in this research to model granular flow must be explained by detail!
4. In Introduction the authors have to add the new published papers about the effect of obstacle on the fluid flow arises from dam break like: https://doi.org/10.1140/epjp/i2019-12592-3
5. The results in the figures are often uninterpretable and of poor quality. Please improve the figures.
6. Comparison of laboratory data and simulation results (Fig. 5) shows a low accuracy of the model, especially after t=7 sec. However the authors explained the possible reason of it in the paper.
7. Figures 8 to 11, how the author interpreted the results in these figures.
8. The references are often old. Please add the new references. 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The article deals with a numerical approach for simulating granular flow-obstacle interaction. As a result, the authors obtained numerous plots of uniform granular stream parameters based on the considered TVD-MacCormack numerical procedure.

However, despite the positive general assessment of the submitted manuscript, the following disadvantages should be eliminated before publication:

1. The research aim/purpose/goal and objectives are not clear. This fact makes it impossible to evaluate the conclusions.
2. The literature review is poor since it is based on the outdated references [1, 2, 3, 4, 5, 10, 18, 19, 20, 21, 23, 27, 28, 30, 31]. I understand that some of them are fundamental studies that can be cited, but not all. Therefore, I recommend removing/updating 90% of these references. Moreover, this review should be analyzed critically.
3. After line 64 and before line 65, I recommend adding available scientific gaps to be addressed during the proposed study.
4. Since the applied governing equations and the corresponding numerical algorithms are well-known, the authors should highlight the scientific novelty of their research.
5. In formula (10b), partial derivatives “du/x” and “du/y” should be fixed and rewritten as “du/dx” and “du/du”, respectively. Moreover, please clarify, what is the value (0.067, 1.234, 0.954, or 5.708), if “du/dx = du/dy = 0”? (It is a really unclear situation with such a mismatch of borders).
6. In figure 5, the authors compared their simulation results with the experimental data previously obtained by Hauksson et al. [29]. Therefore, the authors should substantiate the absence of the granular flow depth’s loss after 6.5 s in the numerical model. Otherwise, there is not clear what is the advantage of the used numerical approach.
7. How the authors can assess the quality of the applied approach (primarily due to figures 5, 8, 9, and 10). E.g., add a relative error, a mean square root, or other quality assessment parameters.
8. According to the results presented in figure 10, the depth of the mass collapse could satisfy a regression model like h = h_max * [1 – exp(-t/tau)], where h_max – a limiting value of the depth, m; tau – specific time like a “relaxation” parameter. In this regard, it is essential to make a regression analysis based on this dependence. As a result, parameters of “h_max” and “tau” could be evaluated.
9. The article should be structured according to the template (e.g., chapters 2, 3, and 4 should be subchapters 2.1, 2.2, and 2.3 of the general chapter “3. Research Methodology”; subchapters 5.1 and 5.2 should be subchapters 3.1 and 3.2 of the general chapter “4. Results”; chapter 7 is empty and should be removed; Declare of interest should be changed from “none” to “The authors declare no conflicts of interest”).
10. Chapter “5. Discussion” is needed.
11. The conclusions are quite poor since quantitative indicators of the aim achievement were not presented transparently.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

This reviewer does not recommend publication of this manuscript. The manuscript is very poorly written, and brings absolutely no novelties. The remarks on this:

• The conclusions section is redefined "Introduction" on methodology
• The conclusion summarizes what authors simulated, not the conclusions. There are no novelties.
• The manuscript feels like a student made a simulation and had written a report
• The tracked depth does not offer new information for scientists or engineers. It is just a forest of captured data
• Shock waves... Is this compressible flow?
• The title itself says it is a report of some kind
• "finite-element scheme" is mentioned in abstract and the used scheme is described nowhere in the paper

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

In my opinion, the manuscript has been sufficiently improved to warrant publication in Applied Sciences.

Reviewer 2 Report

The authors have made all the corrections to improve their manuscript. I recommend this article for publication.

Reviewer 3 Report

This reviewer still does not see any novelty for publication, even with provided updates to the manuscript. The updates are of technical nature, and not scientific nature.