Date of Award
Engineering and Applied Science - Mechanical
Uttam K Chakravarty
The nature of the aerodynamic environment surrounding a helicopter causes a significant amount of vibration to its whole body. Among different sources of vibrations, the aerodynamic loading on the main rotor blade is the major contributor. Therefore, analyzing a rotor blade's vibration characteristics and aerodynamic behavior becomes essential. The vortex characteristics and the wake surrounding a helicopter rotor blade play an important role because they affect the aerodynamic behavior of the rotor blade. An advanced mathematical and computational model of rotor wake and blade vortex gives a better understanding of the helicopter rotor dynamics. This study develops computational models of a helicopter rotor blade to obtain the vibration characteristics and aerodynamic behavior. In addition, a mathematical model of the wake is also used, consisting of the fundamental wake geometry. A Bo 105 helicopter rotor blade is considered for computational aerodynamic analysis. A fluid-structure interaction model of the rotor blade with surrounding air is developed, where the finite element model of the blade is coupled with the computational fluid dynamics model of the surrounding air. The fluid-structure interaction model analyzes aerodynamic coefficients, velocity profiles, and pressure profiles. The resonance frequencies and mode shapes are also obtained by the computational method. A small-scale model of the rotor blade is manufactured, and an experimental analysis of similar contemplation is conducted to validate the numerical results. Wind tunnel and vibration testing arrangements are used for the experimental validation of the aerodynamic and vibration characteristics, respectively. The computational results show that the coefficient of lift increases with the angle of attack up to a critical value. The coefficient of drag also increases with the angle of attack. The elastic rotor blades are subjected to coupled flapping, lead-lag, and torsional (triply coupled) deflections. The resonance frequencies and mode shapes in each direction vary with the size and shape of the rotor blade and the mode number. The wake and vortex analysis showed that the swirl velocity is minimum, and the axial velocity is maximum at the vortex center. The axial velocity decreases, and swirl velocity increases with increasing the distance from the vortex center to the core radius.
Pulok, Mohammad Khairul Habib, "Aerodynamics and Vibrations of a Helicopter Rotor Blade" (2022). University of New Orleans Theses and Dissertations. 3022.
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