General comments
- Scientific relevance: This is a very interesting an important topic and the level of detail is impressive.
- Scientific quality: It is generally of high quality, and sometimes perhaps goes into too much detail. However, I think that the importance of the topic and the lack of similar studies warrants this level of detail. As an additional, I would just like to see an analysis or at least a discussion on how the results could actually be used by wind farm planners in the future.
- Presentation quality: Sometimes the paper is difficult to follow. I hope my suggestions help improve the presentation and arguments.
Specific comments
ABSTRACT:
- Line 4: It's not clear what you mean by "The terrain site". Do you just mean "The site"? Please clarify this.
- Lines 7-8 "In the first part, high-resolution CFD simulations are performed to separately investigate the effects of the forested
escarpment and of thermal stratification on the flow field and on the wind turbine accordingly". I'm not sure what the word "accordingly is doing there. I suggest removing it.
- Line 7: Specify and quantify what you mean by "high-resolution CFD simulations" and include the CFD type, e.g. RANS, LES, etc.?
- Line 8: Why did you investigate thermal stratification? Is the site characterised by strongly seasonal differences? Or by unstable condiitons? Low-level jets? This should be mentioned in the sentence "The site is characterised by ...." starting on line 4.
- Line 9: When you write "all the examined effects" do you mean just the two mentioned in the previous sentence. If so, just write "both these effects" instead.
- Line 12: please quantify the influence of the effects on the flow field, i.e. the average wind speed is affected by up to x%, which could affect the AEP by x% (if you didn't estimate this in the paper, you should...see later)
- Line 17: "....which is important because ????"
1. INTRODUCTION
- Please split this section up into sub-sections. It is difficult to follow.
- Lines 22-23: This statement is too broad. One paper showed that "the time averaged speed-up and the mean inclination can in general be predicted decently", but what does that mean for wind energy in general? You cannot conclude that therefore RANS can predict wind fields well for all wind energy applications. Please discuss this.
- Line 23: define "speed-up"
- Lines 24-25: you need a reference for this. And what does "sufficiently complex" mean? You might want to read and refer to https://wes.copernicus.org/preprints/wes-2021-158/. And why can't these conditions be adequetly modelled by RANS? What does "adequate" mean? Please expand on this section, because it is fundamental to your paper and why your work is important.
- Lines 28-30: please include a reference for this statement
- Line 30: please include a reference about hybrid RANS/LES methods.
- Line 37: "hybrid methods or LES methods usually produce significantly better predictions" implies many studies showing this. Please refer to some of these.
- Line 38: without significantly increasing the computational power? (otherwise why not just use LES?) Please discuss this topic here too.
- Line 39: please specific what "adequate" means in this context. Also, you should refer to https://wes.copernicus.org/preprints/wes-2021-158/ even though it is still a discussion paper (publication expected very soon) because DDES was actually applied to the same site in this work.
- Line 43: you mentioned "the escarpement" - which escarpement? You don't say anything about the site in Belcher et al. Is it the same site or a different one? Please clarify.
- Line 56: "can lead to"....."under certain conditions" (which conditions?) - surely the discrepancy is not present for all possible conditions?
- Line 57: "in power generation." should come directly after "5%"
- Line 57: quantify what you mean by "correct" and then by "accurate" on the next line.
- Lien 68: "to predict the effects of complex terrain on wind turbines more accurately" would be correct English.
- Line 68: specify what you mean by "complex terrain" here.
- Lines 69-70: What do you mean by "Thus, a variety of studies are conducted experimentally and numerically"? Do you mean in general, or in this work? It would be clearer if you wrote "...can be...."
- Line 71: coarser than what? Remember that the reader does not yet know anything about your simulation set-up. Please quantify this instead.
- Line 72: please reference this paper too: https://wes.copernicus.org/preprints/wes-2021-158/
- Line 73: specify what you mean by "highly resolved" (time? spatially? both?) and quantify this.
- Line 74: remove "in complex terrain" - you already said that the test site is complex.
- Line 74: "....and on its wake...."?
- Line 76-81: This part does not belong in the Introduction. Please move it to the set-up. Also, say where these simulations come from. Are they from the results of this study? In which case, it's confusing to show results already at the beginning. Consider removing this figure. I don't see what it's contributing to the paper.
2. SETUP
- Line 92: Specific what you mean by "fully resolved", i.e. how many cells over the rotor? Later on you say 1 m, but how large is the wind turbine?
- Line 98: Why do you say the height is 2500 m here, but 2600 on line 94?
- Line 120: define z+ and explain why it is different from the commonly-used y+.
- Line 126: This isn't very clear - do you mean that you just shifted the z coordinate? Or what else changed in the shift between "turbine position" and "hub position"? Please clarify.
- "2.2 Numerical Set-up": you keep switching tenses - please be consistent (i.e. "is" and "was").
- Line 130-135: Please include a table summarising the set-up.
- Line 164: I find it hard to understand the results of the preliminary study (e.g. I'm not sure what "Thus, this study revealed that cells of the lowest approximately
0.5 m above-the-ground are modelled." really means). I suggest a rewording, and also a figure would help here.
- Line 170: please explain briefly what the "chimera technique" is.
- Line 180: Please specifiy the accuracy of the anemometers and if their set-up was done according to IEC 61400-12 or not.
- "2.4 Forest Setup": it's not clear to me how much of this is in Letzgus et al. 2018 and how much is new (without having looked at that paper). Please make this more obvious.
- Line 192: It's strange to refer to equation (4) here, which is so far away. I would remove this reference, and mention it later next to equation (4).
- "2.5 Inflow Setup": make sure you are consistent with the use of "Mann model" or "Model-model". Also, you define "turbulence intensity" as "Ti" so make sure you use "Ti" instead of "turbulence intensity" in the rest of the paper.
- Line 256: Don't write "his" but "their". First of all, this is gender-neutral. Second of all, it could refer to all the authors rather than just the first author.
- Lines 260-275: It's not clear if you are applying this method here for the first time or whether it has already been done. Please make this clear.
- Line 279: Please indicate why you chose this temperature range. Probably it is a typical range for wind energy applications, but please say where this comes from.
- "2.7 Governing Equations". It's not clear what this section is for. Is this summarising all the changes you made to FLOWer? Please clarify this.
3. RESULTS PART 1
- The introduction is confusing. It's not clear if "the first part of the results" refers to section 3 only, and "the second part of the results" refers to section 4, or whether you are referring to two parts of section 3. Please reword this.
- Figure 5 and Figure 6: please add a length scale to these pictures.
- Line 308: "In general, trees are 20 to 35 meters tall.". Do you mean in general, or in general at this site? Please clarify. Also, where does this information come from, DSM or somewhere else?
- Line 323: The units of LAI are missing, please add.
- Line 325: Please say why you made this assumption?
- Line 361: Explain why you chose to plot SD rather than TI or TKE.
- Line 363: Please explain why you chose four minutes.
- Figures 10-13, 16: Could all be bigger.
- Figure 11: Alter the legend to match the text (i.e. "Labil" should be "unstable")
- Line 385: Explain why at this position.
- I suggest a table to summarise the effects.
4. RESULTS PART 2
- Line 487: You mean "in the second part of the results"?
- Line 497: Define what you mean by "speed-up"
- I suggest a table to summarise the effects.
5. CONCLUSIONS
- I would like to see one further discussion point - how could readers use the results to assess the impact of such flow conditions on AEP and load cycles?
Technical corrections
- Lines 9-10: Don't combine two tenses in one sentence please, i.e. change "shows" to "showed". Also, change "wintertime" to "winter conditions" (although March isn't really winter).
- Line 22: "is" --> "can be"
- Line 23: replace "decently" with "well".
- Line 37: remove the space after "Sogachev et al. (2012)"
- Line 41: space missing after the full-stop.
- Line 75: remove "will"
- Section 2: Change "Setup" to "Set-up" (throughout the paper)
- Line 135: please be consistent in your use of "2-dimensional" and "2D".
- Line 206: I don't think you defined LAI.
- Line 234: You haven't defined ABL |