Comparative Analysis of HLLC- and Roe-Based Models for the Simulation of a Dam-Break Flow in an Erodible Channel with a 90^∘ Bend

Round 1

Reviewer 1 Report

In general, I enjoyed reading the manuscript, the language, the style, the topic and the soundness of the research all live up to the standard for journal publication. 

The only comment that I would like to authors to clarify is that the authors stated that 'hydrostatic pressure distribution' is assumed in the shallow water flow model (Line 88). However, the authors calls the methods as the coupling between the 'hydrodynamic' model and the morphodynamic model. Note that shallow water models can be roughly divided into hydrodynamic(non-hydrostatic) and hydrostatic models based on the pressure assumption. Can the authors clarify the type of flow models that is used. 

This also leads to another discussion here. At the sharp corner in the experiment, disturbance on the free surface occur and the non-hydrostatic pressure plays important roles, also for the sediment transport. Have the authors examined the free surface and thought about applying non-hydrostatic pressure shallow water models, maybe in future research? 

I suggest the authors clarify the flow model and include discussion on the free surface impacts. 

 

Comments for author File: Comments.pdf

Author Response

Comments from the reviewer 1

 

Comment: In general, I enjoyed reading the manuscript, the language, the style, the topic and the soundness of the research all live up to the standard for journal publication.

Ans: The authors thank the positive comments of the reviewer. Modifications in the revised manuscript have been marked in red color.

Comment: The only comment that I would like to authors to clarify is that the authors stated that 'hydrostatic pressure distribution' is assumed in the shallow water flow model (Line 88). However, the authors calls the methods as the coupling between the 'hydrodynamic' model and the morphodynamic model. Note that shallow water models can be roughly divided into hydrodynamic (non-hydrostatic) and hydrostatic models based on the pressure assumption. Can the authors clarify the type of flow models that is used.

Ans: The shallow-type models used in this work assume hydrostatic pressure distribution along the flow column. This has been clarified in the revised manuscript.

Comment: This also leads to another discussion here. At the sharp corner in the experiment, disturbance on the free surface occur and the non-hydrostatic pressure plays important roles, also for the sediment transport. Have the authors examined the free surface and thought about applying non-hydrostatic pressure shallow water models, maybe in future research?

Ans: The authors agree with the reviewer and realize the importance of the assumption made for the pressure distribution, especially when dealing with the highly transient flow at the inner corner region. This key point has been commented throughout the revised manuscript.

Comment: I suggest the authors clarify the flow model and include discussion on the free surface impacts.

Ans: Both reviewer's suggestions have been added to the revised text.

Reviewer 2 Report

The paper presents a comparison of three numerical strategies for the resolution of the system of shallow water and Exner equations. Both capacity and non-capacity conditions have been considered and the performance of test models has been compared against experimental data. The study showed that the non-capacity approach can improve predictions in areas with transient conditions, but a careful calibration of the non-equilibrium parameters is necessary.

Overall, the paper is well written. The introduction provides comprehensive literature review with a clear statement on the aim of the study. Also, the description of methods is adequate. Results section provides detailed presentation of simulation outcomes. The conclusion section might be improved to show broader context of the study by providing comments and suggestions on potential applications or recommendations. In the present form, this section presents a summary of the study and comparison between the models, while it lacks the comment on the future directions of simulations development that are necessary to advance these methods.

I have noticed a typo in line 568 ('bel'). Moreover, I would suggest using units in meters to report distance, e.g. in line 331. In Fig. 1, I suggest replacing commas by dots.

In my opinion, this work is worth to be considered for publication after minor revision.

Author Response

Comments from the reviewer 2

Comment: The paper presents a comparison of three numerical strategies for the resolution of the system of shallow water and Exner equations. Both capacity and non-capacity conditions have been considered and the performance of test models has been compared against experimental data. The study showed that the non-capacity approach can improve predictions in areas with transient conditions, but a careful calibration of the non-equilibrium parameters is necessary.

Overall, the paper is well written. The introduction provides comprehensive literature review with a clear statement on the aim of the study. Also, the description of methods is adequate. Results section provides detailed presentation of simulation outcomes.

Ans: The authors are grateful for the positive comments. Changes in the revised manuscript have been marked in red color.

Comment: The conclusion section might be improved to show broader context of the study by providing comments and suggestions on potential applications or recommendations. In the present form, this section presents a summary of the study and comparison between the models, while it lacks the comment on the future directions of simulations development that are necessary to advance these methods.

Ans: The conclusions have been extended with a qualitative discussion on the method selection when movable boundaries are involved and with future research directions.

Comment: I have noticed a typo in line 568 ('bel').

Ans: This has been corrected.

Comment: Moreover, I would suggest using units in meters to report distance, e.g. in line 331.

Ans: The units have been changed to meters following the reviewer suggestion.

Comment: In Fig. 1, I suggest replacing commas by dots.

Ans: Float commas have been replaced by dots following the reviewer suggestion.

Comment: In my opinion, this work is worth to be considered for publication after minor revision.

Ans: The authors thank this valuable review.