Panel flutter is a typically dynamic aeroelastic instability phenomenon of the external skin panel with one side exposed to supersonic airflow. This phenomenon can lead to fatigue damage and result in serious consequences due to low-amplitude and long-lasting vibration. Therefore, how to suppress panel flutter and reduce the vibration amplitudes is an urgent problem to be solved. In the past, numerous active and passive control methods have been proposed, yet none of them has satisfactorily solved the problem of the panel flutter. The add-on acoustic black hole (AABH), as a vibration reduction device with light weight, rich modal density, and high damping characteristics, has been extensively studied in the vibro-acoustic control of structures. However, there has been no research on its application in the panel flutter suppression. Meanwhile, the prediction of aerodynamic response and flutter boundary of panel structures with attached AABH presents a complex challenge, requiring a sophisticated numerical strategy. Therefore, establishment of a numerical method for coupled aeroelastic analysis of a panel in supersonic flow with AABH and the performance of AABH in suppression of the panel's aeroelastic instability is of great significance.
Recently, the team of structural dynamics led by Hongli Ji and Jinhao Qiu from Nanjing University of Aeronautics and Astronautics, China, utilized the AABH to mitigate panel flutter and introduced a novel approach for coupled aeroelastic analysis of a panel subjected to supersonic airflow. The calculation results show that compared with traditional damping devices, AABH can significantly increase the critical flutter boundary of the panel. By adjusting the geometric parameters and installation positions of AABH, the flutter suppression performance of AABH can be further optimized. This work not only underscores the AABH's potential in enhancing aeroelastic stability, but also provide a foundation for its optimal design.
The team published their work in Chinese Journal of Aeronautics on January 2, 2025.
"In this research article, we introduced a novel approach for coupled aeroelastic analysis of a panel subjected to supersonic airflow, utilizing AABH to mitigate panel flutter. By employing Galerkin's method to discretize aeroelastic equation of panel and applying finite element method to derive a reduced discrete model of AABH, we effectively coupled two substructures via interface displacement, which has greatly improved the computational efficiency of the aeroelastic response of the panel with AABH under supersonic flow." said Hongli Ji, the corresponding author of the paper, a professor at Nanjing University of Aeronautics and Astronautics (China), whose research focuses on the field of structural dynamics, especially analysis and applications of acoustic black hole in vibro-acoustic control.
"Based on the coupled aeroelastic analysis of the interaction forces between the AABH and panel in our work, we have highlighted that the modal effective mass, the discrepancy between the oscillation frequency and the natural frequency of the AABH mode, and the modal damping ratio are the critical factors influencing the individual AABH mode in flutter suppression. In addition, we have found that the choice and application of certain AABH modes can significantly affect the overall structural response under flutter conditions. Therefore, it is crucial to carefully choose effective modal combinations for practical applications in order to achieve optimal performance. This research provides valuable insights into the design and optimization of anti-flutter systems using acoustic vibration control devices such as AABHs. Selection of effective AABH modes, which directly affects the accuracy of the simulations, is closely related to these factors." said Hongli Ji.
The results reveal that AABH can significantly increase the critical flutter boundary of the panel compared with the equivalent mass. Furthermore, AABH outperforms both the tuned mass damper and nonlinear energy sink in flutter suppression. By adjusting the AABH's geometrical parameters to increase the accumulative modal effective mass within the pertinent frequency range, or choosing a suitable installation position for AABH, its performance in flutter suppression is further optimized. These findings not only underscore the AABH's potential in enhancing aeroelastic stability but also provide a foundation for its optimal design.
However, further research is still needed to realize the application of AABH in suppression of panel flutter. In this regard, Hongli Ji also put forward several research directions that may be pursued in future work, including the improvement of the coupled aeroelastic analysis method of the panel structure with AABH, the optimization strategy for the geometric parameters of AABH, and the combination of the AABH structure with traditional damping methods. These efforts will contribute to the final application of the AABH structure in suppression of the aeroelastic response of real-world panels in aerospace engineering.
Other contributors include Zhuogeng Zhang, Jinhao Qiu from the College of Aerospace Engineering at Nanjing University of Aeronautics and Astronautics in Nanjing, China; Kaihua Yuan from the Beijing Institute of Mechanical and Electrical Engineering in Beijing, China; Li Cheng from the Department of Mechanical Engineering at Hong Kong Polytechnic University in Hong Kong, China.
This work was co-supported by the National Natural Science Foundation of China (No. 52235003 & U2241261).
About Chinese Journal of Aeronautics
Chinese Journal of Aeronautics (CJA) is an open access, peer-reviewed international journal covering all aspects of aerospace engineering, monthly published by Elsevier. The Journal reports the scientific and technological achievements and frontiers in aeronautic engineering and astronautic engineering, in both theory and practice. CJA is indexed in SCI (IF = 5.3, top 4/52, Q1), EI, IAA, AJ, CSA, Scopus.
