the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Numerical Prediction of the Aerodynamics and Aeroacoustics of a Horizontal Axis Wind Turbine
Wen-Yu Wang
Yuh-Ming Ferng
Abstract. This study used low-frequency-based numerical methods to predict noise radiating from rotating horizontal axis wind turbine (HAWT) blades. ANSYS FLUENT was used to calculate flow parameters in the vicinity of blade surfaces, as required for the Ffowcs Williams–Hawkings (FW–H) equation. The numerical model was validated against the experimental results from the National Renewable Energy Laboratory Phase VI wind turbine blades. The coupling analysis was integrated with four Reynolds-averaged Navier–Stokes turbulence models and the FW–H equation under different boundary conditions. The SST k-ω and V2f turbulence models produced results in agreement with the available experimental pressure-coefficient and relative-velocity-distribution data. An INER 25-kW HAWT was employed to predict noise frequency distribution at nine points from the tower on the windward and leeward sides under different operating conditions. Noise frequency distributions on the windward and leeward sides showed little differences, whereas those on the left and right sides with respect to the tower were different owing to wind-shear influence. The peak amplitude of the noise was inversely proportional to the increasing distance from the tower but proportional to the wind and rotation speeds.
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Wen-Yu Wang and Yuh-Ming Ferng
Status: closed
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RC1: 'Comment on wes-2023-32', Anonymous Referee #1, 05 May 2023
The paper presents a numerical method based on a commercial code to predict aerodynamic characteristics and noise emissions of HAWT. The CFD solution is coupled with FWH method to assess the noise spectrum at the observer locations. Different turbulence models are tested, and their results are compared with LES and experimental acquisitions.
The paper faces a very interesting problem related to the annoyance of wind turbines located near populated areas. The main aspects of the noise prediction method are touched by the authors, but the description of the single step is quite shallow and not complete.
For instance, the numerical method description is a general discussion of basic CFD concepts without a deeper discussion of the motivation behind setup choices. Classical PDE equations are reported with some typos (e.g. in Eq. 2 the time derivative term is missing), and also the turbulence model description is too detailed: references to the different model formulation should be enough. Same story for the FWH formulation.
Concerning the numerical model validation by using NREL HAWT, some important aspects of numerical simulation are missing: numerical schemes for diffusive and convective fluxes, detailed description od BCs., discussion about convergence criteria and so on. Moreover, is not crestal clear by looking at Fig. 3 that fine mesh performs better in terms of accuracy. Could the authors better explain their conclusions?
Moving to the INER 25-kW turbine, some aspects of the operating conditions are not so clear: why the rotational speed is expressed in m/s? Should it read rad/s or rpn? When the authors discussed the aerodynamic results, they compared the different turbulence model, without discussing the results in detail. Could the author make a thorough discussion of this? Finally, the comparisons on Fig.12 show some discrepancies, could the authors comment on that?
Concerning the noise prediction section, t is not clear how the CFD simulations used for noise predictions are performed. Do they rely on steady or unsteady simulations? Also, the FWH setup is not completely described: where the FWH surface is placed? Which is the sampling rate of the FFT? Moreover, is quite strange to see noise spectra with negative value in dB (that is under the human hearing threshold). In addition, is there a blade passing frequency in the spectra? If so, please discuss a bit on this aspect.
Finally, an English revision of the wording is highly suggested.
Citation: https://doi.org/10.5194/wes-2023-32-RC1 - AC1: 'Reply on RC1', Wen-Yu Wang, 17 Jul 2023
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RC2: 'Comment on wes-2023-32', Anonymous Referee #2, 12 Jun 2023
The reviewed manuscript presents a study aimed at developing an affordable computational fluid dynamics (CFD) method using Reynolds-averaged Navier-Stokes (RANS) simulations to accurately predict aerodynamic noise from wind turbine rotors. Addressing rotor noise is a topic of great significance, as reducing rotor-generated noise can minimize turbine curtailment and increase Annual Energy Production (AEP). However, the manuscript requires several improvements to enhance clarity, address inconsistencies, and strengthen the analysis and discussion.
General Comments:
- The manuscript lacks clarity in several sections, making it difficult to discern the findings and identify the computational model that produces the best results. The language and spelling need improvement throughout the manuscript.
- The discussion on the computational domain and convergence criteria of the simulations is insufficient. Additionally, important mesh characteristics and simulation performance details are missing, hindering a comprehensive evaluation of the simulation quality.
- There is a mixing up of mesh diameter and radius, as well as the definition of rotor rotational speed in m/s.
Specific Comments:
Validation of Numerical Setup (NREL-Phase VI):
- The authors conduct a mesh sensitivity study using two mesh sizes (~2m & ~6m) and compare the results with LES simulation and experimental data. However, there is no clear convergence observed within the results that are shown. The authors should provide a more detailed analysis and discuss the limitations of the mesh sensitivity study or conduct additional numerical experiments until a convergence can be observed.
- The agreement of the LES simulations with experimental data towards the trailing edge is relatively poor. This discrepancy needs to be addressed and discussed in order to provide a comprehensive assessment of the simulation results.
- The discussion on the computational domain should be expanded to assess whether it adequately captures a fully developed rotor wake. Additionally, the convergence criteria for the simulations should be clearly described.
Simulation of the INER 25kW Rotor:
- The use of a 10m cell mesh raises concerns regarding the transferability of the previous mesh convergence study. The authors should address this issue and explain the rationale behind the selected mesh size.
- Figures 5 to 11 compare velocity distributions generated by four different turbulence models. However, the discussion of these results is qualitative, and it is difficult to draw meaningful conclusions. The authors should provide a more detailed analysis, discussing the strengths and weaknesses of each turbulence model in specific cases. Providing additional rotor performance characteristics such as rotor power, thrust or wake velocity distributions could help the reader to better assess the quality of the presented simulations.
- Legends are missing in the velocity plots, which hampers understanding. The authors should include a clear legend to improve clarity.
Noise Prediction and Discussion:
- The authors should clarify that the results are "verified" against an LES simulation, rather than "validated," as the term "verification" is more appropriate.
- The discussion on noise predictions could be strengthened by providing more detailed analysis and comparisons with experimental data or established noise prediction models.
Conclusion:
In conclusion, the manuscript requires substantial improvements to enhance clarity, address inconsistencies, and strengthen the analysis and discussion sections. The authors should focus on the methodology, providing important details regarding the computational domain, convergence criteria, mesh characteristics, and simulation performance. By addressing these issues and highlighting relevant findings, the manuscript can become eligible for publication.
Citation: https://doi.org/10.5194/wes-2023-32-RC2 - AC2: 'Reply on RC2', Wen-Yu Wang, 17 Jul 2023
Status: closed
-
RC1: 'Comment on wes-2023-32', Anonymous Referee #1, 05 May 2023
The paper presents a numerical method based on a commercial code to predict aerodynamic characteristics and noise emissions of HAWT. The CFD solution is coupled with FWH method to assess the noise spectrum at the observer locations. Different turbulence models are tested, and their results are compared with LES and experimental acquisitions.
The paper faces a very interesting problem related to the annoyance of wind turbines located near populated areas. The main aspects of the noise prediction method are touched by the authors, but the description of the single step is quite shallow and not complete.
For instance, the numerical method description is a general discussion of basic CFD concepts without a deeper discussion of the motivation behind setup choices. Classical PDE equations are reported with some typos (e.g. in Eq. 2 the time derivative term is missing), and also the turbulence model description is too detailed: references to the different model formulation should be enough. Same story for the FWH formulation.
Concerning the numerical model validation by using NREL HAWT, some important aspects of numerical simulation are missing: numerical schemes for diffusive and convective fluxes, detailed description od BCs., discussion about convergence criteria and so on. Moreover, is not crestal clear by looking at Fig. 3 that fine mesh performs better in terms of accuracy. Could the authors better explain their conclusions?
Moving to the INER 25-kW turbine, some aspects of the operating conditions are not so clear: why the rotational speed is expressed in m/s? Should it read rad/s or rpn? When the authors discussed the aerodynamic results, they compared the different turbulence model, without discussing the results in detail. Could the author make a thorough discussion of this? Finally, the comparisons on Fig.12 show some discrepancies, could the authors comment on that?
Concerning the noise prediction section, t is not clear how the CFD simulations used for noise predictions are performed. Do they rely on steady or unsteady simulations? Also, the FWH setup is not completely described: where the FWH surface is placed? Which is the sampling rate of the FFT? Moreover, is quite strange to see noise spectra with negative value in dB (that is under the human hearing threshold). In addition, is there a blade passing frequency in the spectra? If so, please discuss a bit on this aspect.
Finally, an English revision of the wording is highly suggested.
Citation: https://doi.org/10.5194/wes-2023-32-RC1 - AC1: 'Reply on RC1', Wen-Yu Wang, 17 Jul 2023
-
RC2: 'Comment on wes-2023-32', Anonymous Referee #2, 12 Jun 2023
The reviewed manuscript presents a study aimed at developing an affordable computational fluid dynamics (CFD) method using Reynolds-averaged Navier-Stokes (RANS) simulations to accurately predict aerodynamic noise from wind turbine rotors. Addressing rotor noise is a topic of great significance, as reducing rotor-generated noise can minimize turbine curtailment and increase Annual Energy Production (AEP). However, the manuscript requires several improvements to enhance clarity, address inconsistencies, and strengthen the analysis and discussion.
General Comments:
- The manuscript lacks clarity in several sections, making it difficult to discern the findings and identify the computational model that produces the best results. The language and spelling need improvement throughout the manuscript.
- The discussion on the computational domain and convergence criteria of the simulations is insufficient. Additionally, important mesh characteristics and simulation performance details are missing, hindering a comprehensive evaluation of the simulation quality.
- There is a mixing up of mesh diameter and radius, as well as the definition of rotor rotational speed in m/s.
Specific Comments:
Validation of Numerical Setup (NREL-Phase VI):
- The authors conduct a mesh sensitivity study using two mesh sizes (~2m & ~6m) and compare the results with LES simulation and experimental data. However, there is no clear convergence observed within the results that are shown. The authors should provide a more detailed analysis and discuss the limitations of the mesh sensitivity study or conduct additional numerical experiments until a convergence can be observed.
- The agreement of the LES simulations with experimental data towards the trailing edge is relatively poor. This discrepancy needs to be addressed and discussed in order to provide a comprehensive assessment of the simulation results.
- The discussion on the computational domain should be expanded to assess whether it adequately captures a fully developed rotor wake. Additionally, the convergence criteria for the simulations should be clearly described.
Simulation of the INER 25kW Rotor:
- The use of a 10m cell mesh raises concerns regarding the transferability of the previous mesh convergence study. The authors should address this issue and explain the rationale behind the selected mesh size.
- Figures 5 to 11 compare velocity distributions generated by four different turbulence models. However, the discussion of these results is qualitative, and it is difficult to draw meaningful conclusions. The authors should provide a more detailed analysis, discussing the strengths and weaknesses of each turbulence model in specific cases. Providing additional rotor performance characteristics such as rotor power, thrust or wake velocity distributions could help the reader to better assess the quality of the presented simulations.
- Legends are missing in the velocity plots, which hampers understanding. The authors should include a clear legend to improve clarity.
Noise Prediction and Discussion:
- The authors should clarify that the results are "verified" against an LES simulation, rather than "validated," as the term "verification" is more appropriate.
- The discussion on noise predictions could be strengthened by providing more detailed analysis and comparisons with experimental data or established noise prediction models.
Conclusion:
In conclusion, the manuscript requires substantial improvements to enhance clarity, address inconsistencies, and strengthen the analysis and discussion sections. The authors should focus on the methodology, providing important details regarding the computational domain, convergence criteria, mesh characteristics, and simulation performance. By addressing these issues and highlighting relevant findings, the manuscript can become eligible for publication.
Citation: https://doi.org/10.5194/wes-2023-32-RC2 - AC2: 'Reply on RC2', Wen-Yu Wang, 17 Jul 2023
Wen-Yu Wang and Yuh-Ming Ferng
Wen-Yu Wang and Yuh-Ming Ferng
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