Comparison of three DWM-based wake models at below-rated wind speeds
Abstract. Wind turbine wake models are essential tools for predicting power losses and structural loads in wind farms. Among them, the dynamic wake meandering (DWM) model, included as a recommended approach in the International Electrotechnical Commission design standard, is a widely used engineering-fidelity method that balances accuracy and computational cost. This study compares the performance of three DWM-based wake model implementations (from the Technical University of Denmark, the National Renewable Energy Laboratory, and the Institute for Energy Technology) under below-rated wind speed conditions. Model predictions of wake flow, power output, and structural loads for a four-turbine row are evaluated across different ambient turbulence levels and wind-direction misalignments, and compared against high-fidelity large-eddy simulation results. All three models captured the overall wake evolution and mean turbine performance with reasonable accuracy; predicted time-averaged thrust and power were typically within 5–10 % of the large-eddy simulation benchmark. However, notable differences emerged in wake structure and unsteady load predictions, with discrepancies increasing for turbines further downstream. These differences highlight the importance of modelling choices such as wake summation and turbulence treatment, which strongly influence power-deficit and fatigue-load predictions. Comparison with large-eddy simulations reveals the strengths and weaknesses of each approach, indicating where improvements are needed. In general, the findings suggest directions for refining DWM models and improving their fidelity, ultimately enabling more robust wake predictions for wind farm design and operation.
A very nice and complete work, pointing out relevant shortcomings in the leading implementations of DWM and putting a legitimate doubt on the use of DMW for fatigue modelling. The work is high quality, showing relevant analyses and pointing out the key observations clearly. Conclusions are backed up by results, and limitations of the study are discussed openly and fairly.
Abstract: OK
1 Introduction:
I think the first sentences (line 17 and 18) mischaracterize the history of wind energy a little, unless “recent decades” includes the 70’s and 80’s, when the first large-scale wind parks were built in Denmark and the US [1].
2 Methodology:
Equation 1 there is something wrong with the notation. The summation from k=1 to N_k suggests N_k is the number of load ranges, but later N_k is also the number of cycles at load range S_k. Please correct the notation, e.g. to a summation from k=1 to K, and adjust the phrasing in line 127 if needed. Further, please define m as the material Wohler coefficient.
IFE model: The superposition of wake deficits is based on Zong et Al, but the summation of wake added turbulence is based on root sum squared. This is an interesting choice and could be pointed out in the text.
3 Results
In lines 485 to 490, frequency content above 1p is discussed. However, no mention is made of the 3p frequency, indicator of asymmetric rotor loading, which for case a) shows up prominently in the LES PSD, but not an any of the DWM models. This is consistent with the observation made on tower loads in lines 512 to 515. These observations are in line with previous literature on asymmetric loading in DWM [2]. A mention of 3p loading could be made in the discussion at line 720, where asymmetric flow in the wake is discussed. The addition of the PDS plots for tower yaw moment in the aligned case should provide further evidence for this phenomenon and would be a valuable addition to the work.
In line 588 we find “The reduced loads due to an increased wind speed”, should it not be due to a “decreased” wind speed? Otherwise, more clarificaiton is needed with respect to what you are comparing against here, ans which figures support this statement.
4 Discussion
In the limitations, the impact of a fully rigid structure should be discussed. Tower load spectra are normally dominated by eigen-frequencies and their harmonics. While the rigid tower allows to analyze the aerodynamic forcing in isolation, overall conclusions on tower DEL may be skewed as the interaction between tower Eigenmodes and DWM is neglected. This should be mentioned.
5 Conclusions: OK
Editorial commends
Line 146: Unnecessary comma.
Lines 182-185: Please revise this sentence.
Line 201: Please revise incomplete sentence: “necessary to model.”
Line 492: Missing a space after comma.
Line 786: No “-“ in fatigue damage.
[1] Möllerström E, Gipe P, Ottermo F. Wind power development: A historical review. Wind Engineering. 2024;49(2):499-512. doi:10.1177/0309524X241260061
[2] V Bernard et al 2024 J. Phys.: Conf. Ser. 2767 092092