Inertial drag and lift forces for coarse grains on rough alluvial beds measured using in-grain accelerometers

Maniatis, Georgios; Hoey, Trevor; Hodge, Rebecca; Rickenmann, Dieter; Badoux, Alexandre

doi:https://doi.org/10.5194/esurf-8-1067-2020

Articles | Volume 8, issue 4

https://doi.org/10.5194/esurf-8-1067-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/esurf-8-1067-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 8, issue 4

Research article

|

21 Dec 2020

Research article |

| 21 Dec 2020

Inertial drag and lift forces for coarse grains on rough alluvial beds measured using in-grain accelerometers

Georgios Maniatis, Trevor Hoey, Rebecca Hodge, Dieter Rickenmann, and Alexandre Badoux

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Final revised paper (published on 21 Dec 2020)
Preprint (discussion started on 03 Apr 2020)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Peer review', Anonymous Referee #1, 11 May 2020
- AC1: 'Reply to Reviewer 1', Georgios Maniatis, 13 Jun 2020
SC1: 'Commentary on the article: Inertial drag and lift forces for coarse grains on rough alluvial beds by Maniatis et al.', Khaldoon AlObaidi, 15 May 2020
- SC2: 'Respnose to comment', Georgios Maniatis, 15 May 2020
  - SC3: 'RE: Response: Commentary on the article: Inertial drag and lift forces for coarse grains on rough alluvial beds by Maniatis et al.', Khaldoon AlObaidi, 15 May 2020
    - AC4: 'Reply to short comment 2', Georgios Maniatis, 13 Jun 2020
RC2: 'Review of esurf-2020-20 by Maniatis et al.', Anonymous Referee #2, 19 May 2020
- AC2: 'Reply to Reviewer 2', Georgios Maniatis, 13 Jun 2020
RC3: 'Review of Inertial drag and lift forces for coarse grains on rough alluvial beds', Anonymous Referee #3, 21 May 2020
- AC3: 'Reply to Reviewer 3', Georgios Maniatis, 13 Jun 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Georgios Maniatis on behalf of the Authors (24 Jul 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (01 Sep 2020) by Claire Masteller

RR by Anonymous Referee #1 (19 Sep 2020)

Suggestions for revision or reasons for rejection

The manuscript by Maniatis et al. is greatly improved from the first version. I mostly have minor suggestions to clarify various points, including how the authors describe and define entrainment. I recommend publication after minor revisions.

7-8: “This paper introduces and tests a theoretical framework that connects the IMU measurements with the forces applied on a sediment grain moving on a riverbed”. To me this sentence still implies that the authors independently “test” their calculations of forces, which they do not. Suggest saying something like they develop a theoretical framework for calculating drag and lift forces on grains that are in motion, based on IMU measurements.

42: remove “and”

58: remove comma after Gimbert et al citation.

116: suggest changing to “… record zero acceleration (and therefore zero net force) until…”

118: Could cite Garcia et al (2007) here for grain vibrations prior to entrainment.

Garcia, C., H. Cohen, I. Reid, A. Rovira, X. U´beda, and J. B. Laronne (2007), Processes of initiation of motion leading to bedload transport in gravel-bed rivers, Geophys. Res. Lett., 34, L06403, doi:10.1029/2006GL028865.

142: remove comma after “equations 1 and 2”. Next line, change e.g to e.g.

169: suggest changing “completely immobile” to “not moving”.

Equation 12: An equation without a relationship operator just feels wrong to me. Add a variable for impulse and an equals sign.

223: YEI capitalized, but not capitalized in line 232, be consistent.

267-269: The definition of “entrainment point” is unclear. To me, “the initiation of the vibration that dislodges the particle by one particle diameter” unambiguously says that entrainment is defined as the moment the particle very first starts vibrating, if later on it moves by one particle diameter before stopping to vibrate. But I don’t think that is what the authors actually mean, because Figure 3 shows “dislodgement” well after the initiation of vibrations, and line 285 says that there were pre- and post- entrainment vibrations (the actual definition given would mean zero vibrations before entrainment).

I am not sure, but my guess is that the authors actually define entrainment as the time when the particle has moved by one particle diameter, as implied in lines 281 and 284. If the time of entrainment is measured entirely by video, say this in the paragraph starting at line 267, because otherwise it is not clear how you know when the particle has dislodged by one b-axis. I also would remove “independently” from line 281, because it implies that entrainment was also measured in some other way, but I don’t think this is true. I think entrainment time was measured from the video, and then the forces and impulses before and after this time were calculated from the IMU data.

Figure 3 instead uses the term dislodgement. Is this different from entrainment? Be consistent, if dislodgement is the same then use the same term; if different then define dislodgement.

The authors should also expand on why they define the threshold of motion as the probability of entrainment > 0.5.

Figure 2 caption, last line: remove “which”.

309: give equation numbers for drag and lift forces.

315: After reading the manuscript, I have a slightly better but still incomplete understanding of why the authors say that the ellipsoid sensor demonstrates a strong influence of lift forces. The issue is that lift forces are smaller, so it seems like they should be less important. And they’re also less well correlated for I vs t. When I first read this I was just confused. I suppose lines 325-327 are the explanation. Maybe the point that I’m missing that the data presented only reflect timeseries that did lead to entrainment? Also, did the authors test whether drag and lift time series are correlated in their actual data? The figure 7 analysis assumes they are independent, but its not clear that they are independent in the actual data. Apologies if it is in the manuscript and I missed it.

Figure 4a: seems like the y axis should be expanded to show the data over more than 10% of the plot area.

387: runon sentence, particles not articles. Change to “…diameter particles. The measured…”

390: there is a bonus “s”.

392: expand just a bit on fully developed flows. I think you mean something like “…flows much deeper than the particle diameters, with fully developed boundary layers.”

413: Are the numbers flipped?

416: I presume instantenuous is another physics term I’m unfamiliar with? Trying to understand the physics in this paper, I sometimes have an immediate feeling of “huh?” … instantenuous. But seriously, this is my favorite new word portmanteau. And I really do like and appreciate the manuscript!

432-435: break into two sentences.

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RR by Anonymous Referee #3 (27 Sep 2020)

RR by Anonymous Referee #2 (10 Oct 2020)

ED: Publish subject to minor revisions (review by editor) (12 Oct 2020) by Claire Masteller

AR by Georgios Maniatis on behalf of the Authors (20 Oct 2020) Author's response Manuscript

ED: Publish subject to technical corrections (05 Nov 2020) by Claire Masteller

ED: Publish subject to technical corrections (06 Nov 2020) by Niels Hovius (Editor)

AR by Georgios Maniatis on behalf of the Authors (07 Nov 2020) Author's response Manuscript

Short summary

One of the most interesting problems in geomorphology concerns the conditions that mobilise sediments grains in rivers. Newly developed smart pebbles allow for the measurement of those conditions directly if a suitable framework for analysis is followed. This paper connects such a framework with the physics used to described sediment motion and presents a series of laboratory and field smart-pebble deployments. Those quantify how grain shape affects the motion of coarse sediments in rivers.