Wall-Modeled and Hybrid Large-Eddy Simulations of the Flow over Roughness Strips
Round 1
Reviewer 1 Report
The paper is very well written and well detailed. Results are well detailed and convincing. I believe it is of significance and should be published.
Author Response
We thank the reviewer for their contribution to this paper.
Some minor changes have been made and the new version has been submitted.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Overall, I found the paper to make a useful contribution to the literature on computing non-equilibrium flows, in this case a step change in roughness. I have some relatively minor criticisms that will need attention before I could recommend publication.
The major point is the comparisons with experiment shown in figure 5. The data could be taken to support either WMLES approaches or IDDES approaches. I would aks the authors to consider this ambiguity more closely. The text refers to the differences in experimental conditions, particularly the Reynolds number and the roughness height. However, the values for Li et al. are not given, and whether the differences are due to Re or ks is not made clear. This distinction would seem crucial for the comparisons made here. The linkage to the velocity profiles shown in figure 7 should also be expanded. Is there a clear conclusion that can be made just based on this evidence?
Note that oil film and near-wall HW measurements are both taken in the laminar sublayer so they should both be OK. This would not be the source of the discrepancy, in my opinion.
Finally, I found figure 10 confusing. The way the wall-normal locations and the methods are indicated is not at all clear in these small figures, and I would ask the authors to consider a better way to plot this data.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The article is well written and only a few comments here:
1) line 110, please add space between vice and versa
2) line 147, \delta here may lead to confusion since some readers may thought this is boundary layer thickness, people typically use h to represent open channel height.
3) figure 4, legend may need to move from figure 4 d) to figure 4 a)
4) figure 6 and 7, is it possible to plot them in a consistent way, which means that both vertical axis represent velocity?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
In this paper, authors presented a study on simulation of flow over alternating roughness strips using WMLES and IDDES. Then they compared the numerical results with experimental data. Reviewer thought that the objectives and the rationale of the study were clearly stated. In this paper, the theory, models (turbulence models, roughness modelling), and grid sensitivity study results were presented in detail. In addition, the authors clearly stated the advantages and limitations of WMLES and IDDES. The conclusions were thought to be drawn by support of calculation results. In the reviewer's opinion, this paper is interesting enough, well prepared and worth publishing in Fluid. Therefore, the reviewer makes a ‘Accept’ decision.
Author Response
We thank the reviewer for their contribution to this paper.
Some minor changes have been made and the new version has been submitted.
Author Response File: Author Response.pdf
