Paul A., Bandyopadhyay A., Das K.P. «Пылевые ионно-звуковые уединенные структуры на звуковой скорости в присутствии нетепловых электронов и изотермических позитронов» Физика плазмы, 45, № 9, с. 848-864 (2019)

Метод псевдопотенциалов Сагдеева и теория, развитая в работе J. Plasma Phys. 78, 565 (2012) используются для изучения пылевых ионно-звуковых уединенных структур, движущихся со звуковой скоростью, в бесстолкновительной незамагниченной пылевой плазме, состоящей из отрицательно заряженных неподвижных пылевых частиц, адиабатических теплых ионов, нетепловых электронов и изотермических позитронов. Данная система допускает существование солитонов как с положительным, так и с отрицательным потенциалом со звуковой скоростью, но не допускает одновременное сосуществование уединенных структур противоположной полярности со звуковой скоростью. Система также допускает существование двойного слоя отрицательного потенциала на звуковой скорости, но не допускает существование двойного слоя положительного потенциала. Хотя система допускает существование суперсолитона положительного потенциала со сверхзвуковой скоростью, но на звуковой скорости не существует суперсолитонов любой полярности. Уединенные структуры исследуются с помощью составного пространства параметров и фазовых портретов динамической системы, описывающей нелинейное поведение пылевых ионно-звуковых волн на звуковых скоростях. В случае, когда в системе нет позитронов, существует двойной слой отрицательного потенциала и суперсолитон отрицательного потенциала со звуковой скоростью, и для этого случая с помощью фазовых портретов обсуждается механизм перехода суперсолитона в солитон после формирования двойного слоя на звуковой скорости. Различия между уединенными структурами на звуковой и на сверхзвуковой скорости анализируются с помощью фазовых портретов.

Chen Bao, Bao Anyu, Zhou Guocheng «Wind tunnel test technologies investigation of civil transport airframe/jet noise installation» Тезисы докладов Шестой открытой Всероссийской (XVIII научно-технической) конференции по аэроакустике (22–27 сентября 2019 г.), с. 77-79 (2019)

Airframe/jet installation noise is one of the main noise sources of civil aircraft. In order to reduce the noise of civil aircraft and acquire the overall noise characteristics of civil aircraft, it is necessary to acquire the sound pressure level, frequency spectrum characteristics of the airframe/jet installation noise and the effect rules of the relative position in the wind tunnel. In order to study the mechanism and characteristics of airframe/jet installation noise in aeroacoustic wind tunnel, the experimental method of airframe/jet installation noise in 0.5m aeroacoustic wind tunnel of AVIC ARI is studied in this paper. The nozzle noise simulation setup, wing support device and directivity measurement array are designed, and the experiment system is formed. The nozzle simulation setup can be installed with variable diameter nozzle, the position of the wing can be changed in the direction of axis and height. The diameter of the microphone phase array is lm, the number of microphones is 63, the distance from the nozzle center is 1.2m, the radius of the directivity arc is 1.8m, the directivity angle is 45–135 degrees and 225–315 degrees respectively with the interval 9 degress between microphones. Microphones are equipped with windproof balls. Secondly, the NACA0012 wing with 127mm chord length and the nozzle with the diameter D 25.4mm are tested in 0.5m aeroacoustic wind tunnel. The noise characteristics of airframe/jet installation effect were studied experimentally. The jet Mach number was 0.9, the free flow Mach number was 0.2, and the height and axial relative position ranges were 0.5D and 1.0D, respectively. The experiment data were obtained. Finally, based on the experiment data, the influence of the relative position of airframe and jet on the noise was analyzed and discussed. The results show that the existence of wing makes the azimuth angle 90 degree point noise. Acoustic pressure level increases to 5 dB, the change of relative position in the axis has little effect on directivity, and the noise pressure level increases when the wing is close to the nozzle in the height direction.

Xiaodong Li, Baohong Bai «Influence of low noise design of large commercial aircraft airframe on certification noise» Тезисы докладов Шестой открытой Всероссийской (XVIII научно-технической) конференции по аэроакустике (22–27 сентября 2019 г.), с. 80-82 (2019)

Considerable efforts have been made to attenuate airframe noise. Several passive and active flow-control techniques have been proposed to reduce the slat low-frequency noise, which is the most prominent component in slat noise spectra in real aircraft Slat cove cover and slat cove filler [Imamura T., Ura H., Yokokawa Y., Enomoto S., and Yamamoto K. “Designing of Slat Cove Filler as a Noise Reduction Device for Leading-Edge Slat,” 13th AIAA/CEAS Aeroacoustics Conference, AIAA Paper 2007-3473] modifications that postpone or eliminate shear layer formation provide significant acoustic benefits. In the case of the cove filler, the broadband noise is reduced by 3–4 dB. However, it is difficult for the slat with cove cover or slat cove filler to retract and form a seamless surface when the slat is not desirable. Alternatively, a blade seal [Khorrami M.R., and Lockard D.P. “Effects of Geometric Detail on Slat Noise Generation and Propagation, International Journal of Aeroacoustics. 2010. Vol. 9, No. 4-5. Pp. 655-678] gives a 2–3 dB reduction at low frequencies (less than 2 kHz), whereas an elongated blade seal eliminates most of the small-scale vortices generated at the cusp. The application of acoustic liner treatments [Ma Z., and Zhang X. “Numerical Investigation of Broadband Slat Noise Attenuation with Acoustic Liner Treatment,” AIAA Journal. 2009. Vol. 47. No. 12. Pp. 2812-2820] can also be used to attenuate the noise. Kopiev et al. [Kopiev V.F., Zaitsev M.Y. and Belyaev I. . “Noise Reduction Potential Through Slat Hook Serrations,” 17th AIAA/CEAS Aeroacoustics Conference, AIAA Paper 2011-2909] suppressed narrowband peaks located in the frequency region 1.5-7 kHz by serrated slat hooks. Kuo and Sarigul-Klijn [Kuo В. C. and Sarigul-Klijn N. “Conceptual Study of Micro-Tab Device in Airframe Noise Reduction: (2) 3D Computation," Aerospace Science and Technology.2012. Vol. 17. No. 1. Pp. 32-39] reduced the deployment angle of the slat to suppress the slat noise, which increases rapidly if the deflected angle of the slat is enlarged. The loss of lift efficiency was compensated by a micro tab implemented at the flap pressure side. Wild et al. 6 attenuated the slat noise by implementing the very long slat chord to lower the speed of the slat trailing-edge flow. However, these noise suppression techniques are far from being applied into the real aircraft, because high-lift devices must satisfy the aerodynamic requirement firstly. An aerodynamic and aeroacoustics optimization design method for high-lift device was established by the authors recently [Wild J., Pott-Pollenske M., Nagel B. “An Integrated Design Approach for Low Noise Exposing High-Lift Devices," AIAA Paper 2006-2843]. The optimization design method integrated the parameterized geometric model, mesh generation, CFD computation and far field noise prediction technique. The optimization design based on a genetic algorithm (GA) was accomplished for multi-element airfoil. The 30P30N three-element high-lift airfoil was selected as the baseline airfoil and optimized in aerodynamic and aeroacoustics. The location and orientation parameters of the slat relative to the main wing, defined by deflection angle, overlap and gap, were optimized to obtain the maximum lift coefficient, which can be calculated by CFD and minimum radiated noise level. The physics-based slat noise model proposed by Guo 68, 99 was applied to predict the high-lift far field noise level. The optimized three-element airfoil was proved to have a better aerodynamic performance and the minimum of the noise level was obtained. In the present paper, the aerodynamic and aeroacoustics optimization design of high-lift device at landing condition will be given. Meanwhile, the gains of airframe noise reduction on certification noise will be evaluated. An airframe noise prediction method based on physics was developed, which can reflect the impact of the low noise airframe configuration and flight path on certification noise. The aircraft certification noise is predicted and the airframe noise contour map is plotted for a particular aircraft. The method can provide a reference for the low noise design of airframe configuration and flight path.