the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
The influence of dune lee side shape
Julia Cisneros
Abstract. Underwater dunes are found in various environments with strong hydrodynamics and sandy, movable sediment such as rivers, estuaries and continental shelves. They have a diversity of morphology, ranging from low to high-angle lee sides, and sharp or rounded crests. Here, we investigate the influence of lee side morphology on flow properties (time-averaged velocities and turbulence). To do so, we carried out a large number of numerical simulations of flows over dunes with a variety of morphologies using Delft3D. Our results show that the value of the mean lee side angle, as well as the value and position of the maximum lee side angle, have an influence on the flow properties investigated. We propose a classification with 3 types of dunes: (1) low-angle dunes (mean lee side < 10°), over which there is no permanent flow separation, except if the maximum slope is steeper than 20° and situated close to the trough, and over which only little turbulence is created; (2) intermediate-angle dunes (mean lee side 10–20°) over which there is generally no permanent but likely an intermittent flow separation, situated over the trough; and (3) high-angle dunes (mean lee side > 20°) over which the flow separates at the brink point and reattaches shortly after the trough, and over which turbulence is high. We discuss the implications of this classification on the interaction between dune morphology and flow.
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Alice Lefebvre and Julia Cisneros
Status: open (until 10 Apr 2023)
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RC1: 'Comment on egusphere-2023-211', Anonymous Referee #1, 20 Mar 2023
reply
Principal criteria
My response to the principal criteria is given in italic.
Scientific significance:
Does the manuscript represent a substantial contribution to scientific progress within the scope of Earth Surface Dynamics (substantial new concepts, ideas, methods, or data)?1. Excellent. There has been considerable debate in recent years about the role of dune lee side morphology in river flow - this paper uses a numerical model to provide a much-needed systematic examination of the impact of lee side configuration on velocity and turbulence over dunes.
Scientific quality:
Are the scientific approach and applied methods valid? Are the results discussed in an appropriate and balanced way (consideration of related work, including appropriate references)?1. Excellent. The authors provide clear explanations of their approach and methods and stick to interpretations based on their results.
Presentation quality:
Are the scientific results and conclusions presented in a clear, concise, and well-structured way (number and quality of figures/tables, appropriate use of English language)?1. Excellent to 2. Good. I provide some suggestions for clarification below.
Access review, peer review, and interactive public discussion
My responses are in italics.
Does the paper address relevant scientific questions within the scope of ESurf?
Yes. The paper focuses on river dunes, an important component of river morphodynamics.
Does the paper present novel concepts, ideas, tools, or data?
Yes. The main novel contribution is the use of a numerical model to examine the effect of various lee side configurations on flow over dunes.
Are substantial conclusions reached?
Yes. The research leads to substantial conclusions that do a good job of summarizing the main results of the research.
Are the scientific methods and assumptions valid and clearly outlined?
Yes.
Are the results sufficient to support the interpretations and conclusions?
Yes. The authors do a good job of using the results of their experiments to support their interpretations and conclusions while avoiding excessive speculation.
Is the description of experiments and calculations sufficiently complete and precise to allow their reproduction by fellow scientists (traceability of results)?
Yes. Their approach could be used to examine other aspects of dune morphodynamics such as patterns of sediment transport over dunes.
Do the authors give proper credit to related work and clearly indicate their own new/original contribution?
Yes.
Does the title clearly reflect the contents of the paper?
No. I think the title needs to be more explicit in terms of the aspects of dune morphodynamics that lee side shape affects. For example, “The influence of dune lee side shape on time-averaged velocities and turbulence”better reflects the content of the paper.
Does the abstract provide a concise and complete summary?
Yes.
Is the overall presentation well structured and clear?
Yes.
Is the language fluent and precise?
Generally yes. I have attached a marked copy of the manuscript with some editorial suggestions.
Are mathematical formulae, symbols, abbreviations, and units correctly defined and used?
Yes.
Should any parts of the paper (text, formulae, figures, tables) be clarified, reduced, combined, or eliminated?
Figure 2: This diagram is confusing. It is difficult to distinguish between the symbols (., * etc) for each configuration. It might be better to use thinner lines for all the profiles.
Lines 172-175: Perhaps I have missed something here, but I don’t understand why mean lee side values of 10 and 17 degrees have been chosen as boundaries for these dune types - additional explanation is required.
lines 277-278: the sentence beginning “For example, Best (2005)….” is confusing - please clarify.
move lines 302-308 to the beginning of section 4.1 so it is clear why the earlier use of 17 degrees has been changed to 20 degrees
lines 319-320: this sentence needs clarification. “Following this assumption, river dunes, in general, are likely to have no or intermittent flow separation and a relatively strong (missing text here?) contained over the trough.
end of section 4.4. The paper and the proposed classification scheme focuses on 2-dimensional dune profiles - dune morphology however is usually three dimensional so I think an additional brief paragraph should be added that considers the role of 3-morphology on dune profiles.
Are the number and quality of references appropriate?
Yes.
Is the amount and quality of supplementary material appropriate?
Yes. However, I don’t understand the explanation in the caption of Figure A1 – please clarify. Also, I think the blue lines are too thick – see my comment on Figure 2 above.
Alice Lefebvre and Julia Cisneros
Alice Lefebvre and Julia Cisneros
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