| Abstract [eng] |
The final project researches the problematics of aeroelastic phenomena at low Reynolds numbers, with experiments related to high-aspect-ratio wings characterized by low mass, thickness and chord length, but large wingspan. Such characteristics result in increased sensitivity to the onset of aeroelastic phenomena, as the wing is highly flexible and prone to bending and torsion under lower airflow loads. In the literature review part, the problematics of aeroelasticity are analyzed, identifying the main types of static and dynamic phenomena, with the main focus on flutter analysis. Key requirements for wing design, modeling and experimental research are also discussed. An overview of the applied methodologies and computational models are provided. In the final project, wing models of different geometries are designed, numerical analysis is carried out to validate geometric characteristics and to determine possible deformation scenarios. Using physical models, the main elastic parameters are calculated: bending and torsional stiffness, which are necessary for the numerical analysis of aeroelasticity phenomena, in order to find instability speeds using the K and P-K methods. The results show that increasing the number of composite layers and decreasing chord length lead to higher airflow speeds required to reach flutter and divergence. Therefore, the most reliable models identified in this project are wings with 2 to 3 layers and chord lengths of 0,02 m to 0,03 m, as their instability speeds met the defined critical airflow speed criteria. For experimental analysis, wing-tip vibration measurement equipment is designed and manufactured. During the experiments, wing-tip vibrations in a wind tunnel are studied using the developed measurement equipment and a laser accelerometer. Vibration and frequency analyses are performed, the experimental results are compared with each other as well as with the numerically obtained instability speed values. The validity of the experiments is supported by similar critical airflow speeds and frequency characteristics indicating the onset of instability. Experiments show that the difference between the flutter speeds obtained from K and P-K methods and experimental data is 0–4%. Divergence speed discrepancies are larger, ranging from 2% to 20%, due to differences between theoretical and actual models geometries and stiffness characteristics. The consistency of results demonstrated that both experimental methods are suitable for investigating aeroelastic phenomena under low Reynolds number conditions, additionally, their combination allows even more reliable evaluation of the dynamic response of the structure and verification of numerical model accuracy. The main objective of the project is to research the aeroelastic phenomena of high-aspect-ratio wings at low Reynolds numbers by integrating the fields of aerodynamics, structural mechanics, composite materials, electronics and data analysis through the application of numerical and experimental methods. |
