HYDRODYNAMICS AND ACOUSTICS

2021 ◊ Volume 2 (92) ◊ Issue 2 ◊ p. 176-190

P. V. Lukianov ^*

^* Institute of Hydromechanics of NAS of Ukraine, Kyiv, Ukraine

BVI-noise generation by a wing-shaped blade of a helicopter rotor

Gidrodin. akust. 2021, 2(2):176-190

https://doi.org/10.15407/jha2021.02.176

TEXT LANGUAGE: Russian

ABSTRACT

Reducing the level of sound emitted by aircraft is one of the urgent problems of the modern aircraft industry. One of the ways to solve it can be the use of propellers with an unconventional configuration to reduce the degree of turbulence of the flow around the blade. Based on this, the paper deals with posing and solving the problem of generating BVI-noise by a wing-shaped helicopter rotor blade. The mathematical statement divides into aerodynamic and acoustic parts with obtaining the solution by a previously developed numerical-analytical method. The behavior of the near and far sound fields has been studied. In particular, the dependences of the distribution of density fluctuations on the longitudinal geometry of the blade, the angle of attack, and the angle of setting the blade to the oncoming flow are obtained. The calculated data of the near field around the blade reveal two distinct longitudinal smoothly distributed peaks. They are present in all considered situations and reflect the blade buckling geometry. In addition, there are two more longitudinal peak series, the amplitude of each of which is one and a half to three times less than that of the previous one. It is shown that an increase in the oncoming flow velocity contributes to the generation of transverse fluctuations on the blade surface, which dominate over the longitudinal fluctuations in terms of level. In general, the level of generated noise is in the range of 50 dB to 60 dB. It is almost 6 dB lower than the noise of the Blue Edge blade configuration and the blade with a rounded tip. In addition, activation of the high-frequency region in the noise spectrum was noticed at a frequency of about 840 Hz. The calculation results indicate that the wing-shaped blade is low noise in the maneuver mode at low flight speeds. The obtained data may be useful in choosing the optimal configuration of the helicopter rotor at the preliminary design stage.

KEY WORDS

aerodynamic sound generation, rotor of a helicopter, blade-vortex interaction, numerical-analytical methods

REFERENCES

[1] R. M. Kufeld, J. L. Cross, and W. G. Bousman, "A survey of rotor loads distribution in maneuvering flight," in American Helicopter Society Aeromechanics Specialists Conference, San Francisco, CA, 1994.

[2] B. D. Roth, "Acoustic source and data acquisition system for a helicopter rotor blade-vortex interaction (BVI) noise reduction experiment," MS Thesis, Naval Postgraduate School, Monterey, CA, 1996.

[3] P. Rauch, M. Geravais, P. Cranda, A. Baud, J. Hirsch, A. Walter, and P. Beaumier, The design, development and testing of a new blade concept, Virginia Beach,VA, May 2011, ch. American Helicopter Society 67th Annual Forum, p. 14.

[4] Y. Delrieux, "From design to flight testing: Overview of rotocraft acoustic research at ONERA for industrial application," Aerospace Laboratory Journal, no. 7, pp. 1-10, 2014.

[5] B. S. Mattos, Overview of rotorcraft technology and market, 2011.

[6] P. V. Lukianov, "Effect of the attached tip vortex of a helicopter blade on BVI noise generation," Cherkasy University Bulletin: Applied Mathematics. Informatics, no. 18(311), pp. 46-58, 2014.

[7] P. V. Lukianov, "Sound generation by Taylor and Scully vortexes and the blade of the varying cross section," KPI Science News, no. 4(96), pp. 139-145, 2014.

[8] P. V. Lukianov, "On one model for aeroacoustics of viscous compressible gas. Part I. Analysis of existing models, deducing of resolving system of equations," Acoustic Bulletin, vol. 16, no. 2, pp. 18-30, 2013-2014.

[9] P. V. Lukianov, "On one model for aeroacoustics of viscous compressible gas. Part II. Noise of the near helicopter blade-vortex interaction," Acoustic Bulletin, vol. 16, no. 3, pp. 31-40, 2013-2014.

[10] P. V. Lukianov, "On one numerical-analytical approach to solving of a problem on sound generation by a thin wing. Part I. General schematic of application to planar stationary problem," Acoustic Bulletin, vol. 14, no. 3, pp. 46-52, 2011.

[11] P. V. Lukianov, "On one numerical-analytical approach to solving of a problem on sound generation by a thin wing. Part II. A schematic of application to non-stationary problems," Acoustic Bulletin, vol. 15, no. 3, pp. 45-52, 2012.

[12] P. V. Lukianov, "The effect of blade tip truncation type on the BVI-noise level," Acoustic Bulletin, vol. 17, no. 2, pp. 23-37, 2015.

[13] L. Y. Gutin, "On the sound field of a rotating propeller," Zhurnal Tehnicheskoi Fiziki, vol. 5, no. 6, pp. 899-909, 1936.

[14] P. V. Lukianov, "Generation of the blade-vortex interaction noise in the case of oblique flow," Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics, no. 4, pp. 81-86, 2014.