BVI-noise simulation of two-blade helicopter's rotor sin-shape
Abstract
It is known that in alive nature every kind of animals improved their appearance for ages. That is why cars and air vehicles try to get a shape, which approximately like animals. For a last time helicopters blades are modeled like bird wing. In this paper a problem of BVI-noise generation by two-blade rotor sin-shape has been set and numerically solved. First aerodynamical problem is solved: blade is interacts with incoming from infinity flow. This flow, in addition to redistribution of velocity and pressure, causes sound generation of aerodynamical by nature. In the paper it was used earlier offered model of author. This model allows extract sound out of unsteady anisotropic flow. A sound density and a pressure level for far and near-field have been calculated. A comparative analysis of the data with ones for two-blade rotor with rectangular blades has been carried out. Sin-shape rotor noise for most case of calculations has 3-5 Db less then the noise of rotor with rectangular blade. The numerical data show that rotor with blades of sinusoidal shape is less noisy then rotor with rectangular blades. This takes place because sinusoidal shape of the blade favors more homogeneous redistribute of sound energy of the incoming flow along the blade. New s-waves fronts appear. Here essential reapportionment of energy of longitudinal sound waves to s-waves is observed. Main factors which influence at sound generation process are not only blade shape but value of blade bending as well. Interference that is seen at the presented figures says about complex non-liner character of generated sound. Its specter activates more high frequencies. Blade shape variation along the blade sweep allows controlling character and level of BVI-noise.
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References
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Citations
BVI-noise generation by wing-shaped helicopter blade
(2020) V. N. Karazin Kharkiv National University. Ser. Mathematics, Applied Mathematics and Mechanics
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