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https://doi.org/10.5194/wes-2025-263
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wes-2025-263
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
21 Jan 2026
| 21 Jan 2026
Status: this preprint is currently under review for the journal WES.
Aeroelastic Validation of ExaWind for the Pazy Wing Wind Tunnel Experiment
Abstract. This paper presents the results of a validation campaign of the fluid-structure interaction capability of the ExaWind software suite using the Pazy wing case, an aeroelastic benchmark featuring large nonlinear deformations of a very flexible wing under low-speed conditions. The simulations used the incompressible Reynolds-averaged Navier–Stokes equations equipped with a Shear-Stress Transport turbulence model for the fluid dynamics, together with a geometrically exact nonlinear beam model for the structural dynamics. The simulations yielded predictions of pre-flutter static deflections and flutter onset speeds that demonstrated strong agreement with both wind-tunnel data and the computational results contributed to the Large Deflection Working Group of the 3rd Aeroelastic Prediction Workshop.
How to cite. Matula, N., Yalla, G., Lee, B., Vijayakumar, G., deVelder, N., Cheung, L., Sprague, M., and Crozier, P.: Aeroelastic Validation of ExaWind for the Pazy Wing Wind Tunnel Experiment, Wind Energ. Sci. Discuss. [preprint], https://doi.org/10.5194/wes-2025-263, in review, 2026.
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Neil Matula
CORRESPONDING AUTHOR
Sandia National Laboratories, Albuquerque, NM, USA
Gopal Yalla
Sandia National Laboratories, Albuquerque, NM, USA
Bumseok Lee
National Renewable Energy Laboratories, Golden, CO, USA
Ganesh Vijayakumar
National Renewable Energy Laboratories, Golden, CO, USA
Nathaniel deVelder
Sandia National Laboratories, Livermore, CA, USA
Lawrence Cheung
Sandia National Laboratories, Livermore, CA, USA
Michael Sprague
National Renewable Energy Laboratories, Golden, CO, USA
Paul Crozier
Sandia National Laboratories, Albuquerque, NM, USA
Short summary
This paper presents the results of a validation campaign of the fluid-structure interaction capability of the ExaWind software suite using the Pazy wing case, an aeroelastic benchmark featuring large nonlinear deformations of a very flexible wing under low-speed conditions. The results show good agreement with the published experimental and simulation results for tip deflection and flutter onset speed, and provide credibility evidence for the predictive capability of the ExaWind suite.
This paper presents the results of a validation campaign of the fluid-structure interaction...
Altmetrics
Review of Â
Aeroelastic Validation of ExaWind for the Pazy Wing Wind Tunnel Experiment, by Neil Matula et al.Â
The paper is well written and addresses the relevant scientific questions of the accuracy of FSI style modeling of slender wings. The methods applied are not necessarily new, but the validation of the open source ExaWind software stack is relevant for the wind community and should have a broad international interest.Â
The paper is well structured, and the objective of documenting the capabilities of predicting stability of slender wings is clear. The scientific approach is generally well described, and only minor details are unclear.Â
In the present work, some approximation of the actual wind tunnel geometry and the wing setup is done. The present reviewer considers the approximations acceptable but is worried that neglecting the tip bar attached to the wing in the CFD setup might have some relevant influence on aerodynamics. It would be good with some discussion on this. One could make a very simple mesh around the tip bar and investigate the aero during a forced motion to evaluate the approximation.Â
As both eigenfrequencies and twist angles are available in the experiment, the present reviewer finds it relevant to compare these, especially as modern wind turbines have considerable torsional degree of freedom.Â
The comparisons with measurements are well discussed but should include the above discussion of twist and frequencies. I don’t expect that including the twist information will change the clear conclusion that the FSI can reproduce the exp.Â
The title is well chosen, and the abstract is to the point; the document is well structured and well written. The figures and tables are easily readable.Â
The main shortcoming of the paper is the references, where essentially only references withing the ExaWind community are given. It would be appropriate to position the work in context to other publications of blade resolved aeroelasticity in wind energy, and other codes used in the wind energy community, as this is the intended application.Â
Besides this shortcoming, I consider it an excellent and valuable paper.Â
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Mandatory changesÂ
It is mentioned in the text that the structural model is sub-stepping within each CFD time-step. It would be appropriate to mention how the loads are estimated at the intermediate time steps on the structural side.Â
Include comparison of eigenfrequencies (maybe a table) and twist angles.Â
The work should be positioned in an international context; there are several international groups among others at Univ. Stuttgart, DLR and DTU Wind and Energy Systems who have worked intensively on FSI of blade resolved flows.Â
Minor details and typosÂ
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Fig 4, Page 11: In my pdf the time step is shown as 10^5 not 10^-5 as intended etc.Â