Date

2021-2-4

Author

Atalay, Mehmet Melih

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The noise of the rotorcraft has become nonignorable with their increasing use in daily life. The aerodynamically active components such as the main and tail rotors are the primary sources of noise, and therefore, their evaluation during the design phase must also be carefully included. Pressure variations caused by several aerodynamic mechanisms on the rotor blades are responsible for the generation of the noise, which may be obtained by computational fluid dynamics. Along with rotor locked self pressure fields, the tail rotor being in the main rotor wake and exposed to strongly nonstationary airflow also need attention. Hence, full helicopter modeling is required to have an accurate evaluation on the tail rotor. However, this modeling and solution are costly for computational fluid dynamics. Therefore, an alternative approach for acoustic analysis is developed in this study. Accordingly, the goal of the thesis is to propose a coupling methodology between comprehensive rotorcraft analysis and an aeroacoustic solver, and to implement of the methodology for investigation of scissors tail rotor. Firstly, the comprehensive analysis approach is validated using available required power data and sectional blade airloads. Then, the proposed presv sure distribution methodology is implemented to couple comprehensive analysis approach and acoustic solver. A CFD generated airfoil pressure database is used to find pressure distribution over each blade section. Additionally, this coupling is validated using sectional loads and acoustic pressure. Furthermore, aerodynamic and aeroacoustic behavior of the tail rotor are evaluated for isolated and main rotor interacted conventional tail rotor configuration. Finally, effects of vertical distance and scissors angle on aerodynamic and aeroacoustic behavior of the main rotor interacted scissors type tail rotor configuration are investigated. Results indicate that the main rotor wake has a significant impact on the tail rotor at certain flight conditions conditions, and vertical distance and scissors angle changes the oscillatory loads, and there are scissors tail rotor configurations which offers lower noise level than conventional tail rotor.

Subject Keywords

Comprehensive analysis, Pressure distribution methodology, Aeroacoustic, Scissors tail rotor

URI

https://hdl.handle.net/11511/89620

Collections

Graduate School of Natural and Applied Sciences, Thesis