the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
An Open Database of High-Fidelity, Multi-Reynolds Airfoil Polars for Wind Turbine Blade Design
Abstract. This paper presents an open-access dataset that has been realized to provide high-fidelity aerodynamic polars for a wide range of wind turbine airfoils, computed using a consistent Computational Fluid Dynamics (CFD) methodology. The database includes lift, drag, and moment coefficients across multiple Reynolds and Mach numbers. Coefficients are computed with both fully turbulent and free transition boundary layers. A blend of the free transition and fully turbulent coefficients is also included. Beyond the stall region, state-of-the-art post-stall extrapolation models are used, the calibration parameters of which are derived from a number of high-fidelity calculations at various angles of attack in separated flow. The data is relevant for wind turbine design, modeling, and simulation, and reflects representative airfoil performance along the span of modern, large-size offshore rotors. The database includes FFA-W3, FFA-W2, FFA-W1, DU, FX-77 and the recently developed OSO families of airfoils. All simulations are performed using validated numerical methods and span a range of conditions typical for utility-scale offshore turbines. The paper discusses the dataset and its key differences with other open-access data, as well as some general trends that can be noted in the aerodynamic coefficients; such a discussion is made possible by the volume of data produced and is specifically tailored to wind turbine applications.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Wind Energy Science.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: closed
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RC1: 'Comment on wes-2025-257', Anonymous Referee #1, 08 Dec 2025
- AC1: 'Reply on RC1', Alessandro Bianchini, 18 Feb 2026
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RC2: 'Comment on wes-2025-257', Anonymous Referee #2, 15 Jan 2026
- AC2: 'Reply on RC2', Alessandro Bianchini, 18 Feb 2026
Status: closed
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RC1: 'Comment on wes-2025-257', Anonymous Referee #1, 08 Dec 2025
In this paper, the authors conduct high-fidelity URANS simulations on different airfoil families to determine the aerodynamic coefficients under a wide variety of operating conditions. Overall, the current research contributes to improving the understanding of blade design and efficiency using new types of airfoils and providing a complete database to be used by the community for this purpose. Before conducting the final simulations, the authors carefully conduct domain, grid and timestep sensitivity analyses. The data set provides a solid foundation for future research to build upon and offers novelty by incorporating compressibility effects. However, the main weakness of the paper is the lack of clarity in several key justifications or model assumptions, which makes the computational setup and results difficult to interpret.
After reviewing the manuscript, I have grouped my comments into two categories, major concerns and minor corrections/suggestions.
Major comments:
- Overall, the text is poorly written. Below are the main issues that should be addressed:
- First of all, the authors do not cite properly the references. Throughout the entire text citations in brackets are used, without differentiation between \cite and \citep commands (if written in latex). Since this happens in the entirety of the text, it really decreases its quality.
- Secondly, hyphens and en dashes are not used appropriately, or authors are not consistent with their use throughout the whole text. For example, in some parts free-stream is used and in others freestream. Please check the regulations on hyphens, en dashes and em dashes and the specific comments in the minor suggestions section below.
- Punctuation after equations is not used at all. After each equation a comma or a full stop should be added. Except if they are followed by ‘and’ or unless punctuation is not required at all.
- Moreover, equations are not referenced correctly. Equations should be referred to by the abbreviation "Eq." and the respective number in parentheses. For example: in Eq. (4). Referencing the equation before stating the formula is also redundant, see Lines 258 and 260.
- SI units are not in the correct format. Regarding the notation of SI units, if units of physical quantities are in the denominator, contain numbers, and are abbreviated, they must be formatted with negative exponents (e.g. 10 km h-1instead of 10 km/h) (see Table 2 in the manuscript).
- There are major capitalization errors. Titles and headings follow sentence-style capitalization (i.e. first word and proper nouns only). This applies to table and figure headings as well. For example, in the text there are mentions of Lift-to-Drag ratio.
- There are many sentences that are too long to read and follow. For more details see minor comments below. Also please check for articles missing, such as ‘the’.
- The paper is missing a clear structure. First of all, in the introduction itself a paragraph (usually at the end) outlining the overall structure of the paper and the story is not present. Moreover, the authors in no Section used introductory paragraphs to explain the purpose of each section, making the paper and the flow hard to follow.
- The most concerning issue is the captions under figures. Almost every caption is wrong. The description does not align with the variables presented in the figures, references are cited wrong, sometimes the legends/labels do not much the plotted lines, variables used in legends are not fully explained and plot limits are sometimes wrong. Moreover subcaptions, such as (a),(b) are used incorrectly and inconsistently. In the minor comments section, the specific instances are further explained.
- The initialization of the URANS simulations in Section 3.1 requires further clarification. Although the authors state that the simulation starts from steady RANS fields, it is not specified whether these RANS computations were laminar, turbulent, or included transition modeling. Moreover, the inflow conditions should be specified.
- In Section 3.1, where the domain sensitivity analysis is conducted several critical details are missing.
- In the current domain setup, how long is the domain in the streamwise direction? Is it enough for the wake to develop and for possible disturbances to not contaminate the flow around the airfoil?
- Moreover, the Mach number should be specified as well, and if incompressible operation is taken into account it should be justified why this was selected over compressible scenarios.
- Finally, the grid refinement between the domains should be explicitly mentioned and justified, as changing mesh resolution could influence numerical dissipation and turbulence resolution.
- Regarding the timestep sensitivity analysis, stability should be also ensured apart from convergence. The timestep is reported in terms of chord flow-through times, but this does not directly indicate the local stability of the scheme. Therefore, the corresponding CFL numbers should be also reported.
- The title in Section 3.2 is quite misleading. This section serves more like a validation study against reference data, than a quantification of compressibility effects. The considered Mach number is very low for compressibility to have a significant effect and justify a 2.2% reduction . It would be helpful to confirm this behavior by performing a similar comparison at a more representative Mach number. The results and the goal of this paper could become more substantiated if a comparison with low-order methods could be added, so the differences and the advantages of the current methodology and subsequent dataset would be highlighted.
- For the SBES simulations presented in Section 3.4, post-stall regime is also modeled. However, the authors do not explain how timestep was selected. Capturing unsteady stall phenomena typically requires a significantly finer timestep than pre-stall conditions. The authors should therefore provide and clarify the criteria based on which the timestep was selected.
Minor comments:
- Attention should be paid to compound adjectives and their use throughout the entire text. For example lines 9,17: free-transition boundary layers, wind-turbine applications. Modifications should be done accordingly throughout the whole manuscript for similar occasions.
- Line 24: suffering is redundant here.
- Line 30: “which made scaling…in an unsteady environment, within which wind-turbine blades typically operate, challenging”. This sentence needs rephrasing.
- Line 32: Check reference as author/s is/are not mentioned.
- Line 39: Bending, to the cube of.
- Line 41: Repetition of word development. Sentence should be rephrased.
- Line 49: the word privileged is suggested to be replaced. (e.g., prioritized).
- Line 64: not available in open access.
- Lines 66-67: DTU 10~MW, IEA 10~MW etc. A space should exist between the number and the SI units. Also between numbers and % a space should be added.
- Line 71: open-access should not have a hyphen (except if used as an adjective). Be more consistent on the use of hyphens throughout the text.
- Line 74: the Reynolds numbers.
- Line 74: data is countable, therefore plural should be used. Please correct throughout the text.
- Lines 78-81: The sentence is too long. Please rephrase and split.
- Lines 92-95: Sentence should be split as it is currently too long.
- Line 97: is approximately.
- Line 97: in the ones of -> for.
- Line 99: “(Timme,2020)” Please be careful with the citation commands. Use \cite or \citep where necessary and correct throughout the whole text. Which-> who.
- Line 107: being used is redundant and repetitive.
- Line 108: near-stall region.
- Line 114: multiple airfoil families…between airfoil families. Repetition.
- Line 120: thickness-to-chord.
- Line 132: numbers can exceed. The Reynolds and … numbers.
- Line 133-134: use punctuation in Equations and formulas, please correct through the text.
- Line 136: T is the temperature. Should be $T$, so the font matches with the font of the equation.
- Line 139: Section. Capital s.
- Line 140: “if” is redundant.
- Line 143: “is increasingly limiting”, maybe consider replacing with “is becoming increasingly limiting”.
- Lines142-145: Long sentence.
- Line 145: URANS -> Explain abbreviation. Make sure you mention and explain abbreviations at the first instance of use. (Correct also line 169).
- Line 150: Parameters used.
- Line 164: consider replacing the word “insist” as it is not fully appropriate in this context.
- Lines 170-173: Long sentence, please rephrase.
- Line 194: “extremely distant” needs to be rephrased.
- Line 198: The word “perusal” is not commonly used, maybe consider replacing it.
- Line 205: Be careful with the use of capital letters in the captions. Capitals should be used only at the start of each sentence. Moreover the caption seems wrong as it depicts the maximum lift to drag ratio error, the lift coefficient and lift to drag ratio. Finally, make sure to explain all variables mentioned in legends and labels. (such as variables D,C).
- Line 210: the word “used” is quite repetitive.
- Line 209-210: Again the panels in the caption do not seem to align with the panels in the figures. Also, please remain consistent on how you use subcaptions (a),(b) etc. as they should come after the variable/panel they describe in the caption. For example: Lift coefficient (a), drag coefficient (b) etc.
- Table 4 title should be rephrased. Maybe “Number of total and chordwise elements” sound better. Articles are also missing. ‘The tested’ should be added.
- Line 224: Caption in Figure 7 is incorrect. Beware this is lift and drag coefficients. Moreover, explain what is Ec. Citations is not correctly referenced in most captions. Finally, the markers and linestyles are not consistent between the legend and the plotted data. In panel 7(c), between 10-15 deg , there seem to be scattered points for the 1000 Ec and 1300 Ec cases that do not fall on the plotted lines. Please explain why this is the case.
- Figure 8: Correct caption based on previous comments. Explain the axes and variables correctly, as well as the legend and variables in them. Where is tf defined?
- Line 230: While the lift…, the drag…5 to 10 timesteps per chord…
- Line 232: Further decrease does not…
- Line 238: “shown in Figure (c,d)”. There is no panel d. Please use and refer to the correct Figures and subfigures.
- Figure 9: Caption is wrong. Please include in the labels also the reference data.
- Line 253: in mind and were…Be consistent with the tenses.
- Line 253&256: “freestream” and “free-stream”. Be consistent on the terminology you use throughout the text.
- Line 254: “However” is redundant.
- Line 268: experimental and numerical results (ones is not needed).
- Line 272: Wrong equation referenced.
- Line 273: lift-to-drag ratio is also mentioned as Lift to Drag ratio in other instances. Please double check and use one terminology in the manuscript. Moreover, check for missing articles (the lift-to-drag ratio at low angles).
- Line 273: for the computation of the entire…
- Figure 10: Correct caption. (a), (b) and (c) should go after the variables/panels they describe.
- Line 286: Simulations simulations. (Repetition)
- Line 288: blends an LES.
- Line 306: Ranges should be indicated with an en dash.
- Line 307: “full domain totals”, please rephrase.
- Line 313: The strong…
- Line 321: The moment coefficient…
- Figure 12: Correct references.
- Line 356: “The separation point is derived (by?)”…
- Line 370: influences.
- Line 405: Wrong Figures are referenced.
- Figure 15: First, please indicate on the x-label the magnitude of the Re numbers. Moreover, once again rephrase the caption. Capital letters or lower case letters in variables are used randomly and subcaptions are not in the correct positions.
- Line 428: Wrong figure reference.
- Line 436: There is no Figure 17(c).
- Figure 16: In the legend there are the dot markers for the experimental data but these are not plotted. Moreover, panels (d) and (h) fall out of bounds. Based on previous corrections, the caption needs to be again adjusted.
- Line 445: Figure X? Correct reference.
- Figure 19: Please correct the caption, the variables explained are not correct. The x-axes for the Reynolds number should indicate the order of magnitude.
- Line 477,478: bend—twist, shear—twist (use en dash as it shows equal relationship between words).
- Line 478: increase broaden ( please rephrase and use one of these verbs).
- Line 478: optimal.
- Figure 20: Please adjust based on previous comments.
- Line 541: Correct reference.
- Figure 11: This figure does not offer something in the discussion. Should it be used, please discuss in more details.
- Figure 18: This figure is a repetition of Figure 16. The experimental data could be plotted with the respective simulations of Fig. 16. Moreover, around 6 degrees and 9 degrees two y-values are reported. Please double check.
- Figure 10: It is not completely clear to which model and parametrization each linestyle is referring to in the legend.
Overall, the manuscript needs major changes and rewriting before considering for publication. If all comments as described above are addressed, I recommend that the manuscript should be accepted.
Citation: https://doi.org/10.5194/wes-2025-257-RC1 - AC1: 'Reply on RC1', Alessandro Bianchini, 18 Feb 2026
- Overall, the text is poorly written. Below are the main issues that should be addressed:
-
RC2: 'Comment on wes-2025-257', Anonymous Referee #2, 15 Jan 2026
- AC2: 'Reply on RC2', Alessandro Bianchini, 18 Feb 2026
Data sets
High-Reynolds Wind Turbine Airfoil Database Francesco Papi et al. https://doi.org/10.5281/zenodo.15706283
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- 1
In this paper, the authors conduct high-fidelity URANS simulations on different airfoil families to determine the aerodynamic coefficients under a wide variety of operating conditions. Overall, the current research contributes to improving the understanding of blade design and efficiency using new types of airfoils and providing a complete database to be used by the community for this purpose. Before conducting the final simulations, the authors carefully conduct domain, grid and timestep sensitivity analyses. The data set provides a solid foundation for future research to build upon and offers novelty by incorporating compressibility effects. However, the main weakness of the paper is the lack of clarity in several key justifications or model assumptions, which makes the computational setup and results difficult to interpret.
After reviewing the manuscript, I have grouped my comments into two categories, major concerns and minor corrections/suggestions.
Major comments:
Minor comments:
Overall, the manuscript needs major changes and rewriting before considering for publication. If all comments as described above are addressed, I recommend that the manuscript should be accepted.