• Title, Summary, Keyword: Aerodynamic Noise

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Whirl Flutter Analysis of a 2-DOF Rotor-Nacelle System Using Quasisteady Aerodynamic Theory (준정상 공력이론을 이용한 2자유도계 로터-낫셀 시스템의 훨플러터 해석)

  • Kim, Dong-Hyun;Yang, Yong-Joon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.7
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    • pp.843-850
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    • 2005
  • In this study, simplified whirl flutter analyses using quasisteady aerodynamic theory have been Performed for a 2-DOF tiIt-rotor system with both pitch and Yaw motions of a rotor-nacelle. The present dynamic system consists of the rotor (propeller) , forming the gyroscopic and aerodynamic element, supported horizontally by a pylon that is pivoted at some wing attachment point. Several design parameters for rotor-nacelle system are considered to practically investigate the effects of whirl flutter stability.

Whirl Flutter Analysis of a 2-DOF Rotor-Nacelle System Using Quasisteady Aerodynamic Theory (준정상 공력이론을 이용한 2자유도계 로터-낫셀 시스템의 훨플러터 해석)

  • Yang, Yong-Joon;Kim, Dong-Hyun;Jung, Se-Un;Kim, Hyun-Jung;Alexander, Boby
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.301-307
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    • 2005
  • In this study, simplified whirl flutter analyses using quasisteady aerodynamic theory have been performed for a 2-DOF tilt-rotor system with both pitch and yaw motions of a rotor-nacelle. The present dynamic system consists of the rotor (propeller), forming the gyroscopic and aerodynamic element, supported horizontally by a pylon that is pivoted at some wing attachment point. Several design parameters (or rotor-nacelle system are considered and the effect of whirl flutter stability are also investigated for various design parameters.

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Analysis of Flexible Media by Dynamic Elastica Theory with Aerodynamic Force (공기저항이 고려된 Dynamic Elastica 이론을 통한 유연매체의 거동해석)

  • Hong, Sung-Kwon;Jee, Jung-Geun;Jang, Yong-Hoon;Park, No-Cheol;Park, Young-Pil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.547-550
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    • 2005
  • In many machines handling lightweight and flexible media, such as automated teller machines and printers, the media must transit an open space. It is important to predict the static and dynamic behavior of the sheets with a high degree of reliability The nonlinear theory of the dynamic elastica has often been used to a nonlinear dynamic deflection model. In this paper, the governing equation is derived and simulated by the finite difference method. The analysis has to include aerodynamic effect for more exact behavior analysis, because the flexible media can be deformed drastically by a little force. Therefore aerodynamic force must be applied to the governing equation. Different results were obtained with and without aerodynamic effect and the resulted show that after contacting circular guide, the directions of flexible media of two cases are different.

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Status of Helicopter Rotor Noise Technology Development in KARI (KARI의 헬리콥터 로터 소음관련 기술개발 현황)

  • Hwang, Chang-Jeon;Chung, Ki-Hoon;Song, Keun-Woong;Joo, Gene;Lee, Wook
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.187-192
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    • 2006
  • Helicopter noise has been considered as one of major design factors like a performance and safety since the public acceptance, comfortability and stealth aspects were important for customers. According to the airworthiness regulation, the noise levels in throe different flight conditions shall comply with the specific limits. Main and tail rotors noise is most dominant in far field due to the low and mid range frequency characteristics. It is an air-born noise so That the accurate aerodynamic data is necessary for the accurate noise prediction. In KARI, low noise main and tail rotors as well as analysis codes have been developed since 2000. The approach for low noise main rotor is a kind of tip modifications, so called twin vortices tip to reduce the BVI noise. Analysis results show the 9.3dB reduction in terms of pseudo EPNL. The uneven spacing concept is applied for low noise tail rotor. Three or four decibel noise reduction is achieved by new optimized uneven spacing. Rotor noise and aerodynamic prediction codes have been improved also.

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Aerodynamic Noise Analysis Using the Permeable Surface for UH-1H Rotor Blade in Hovering Flight Condition (UH-1H 로터 블레이드의 제자리 비행 시 투과면을 이용한 원방 소음 해석)

  • Kim, Ki Ro;Park, Min Jun;Park, Soo Hyung;Lee, Duck Joo;Park, Nam Eun;Im, Dong Kyun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.5
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    • pp.376-384
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    • 2018
  • The aerodynamic far-field noise was computed by an acoustic analogy code using the permeable surface for the UH-1H rotor blade in hover. The permeable surface surrounding the blade was constructed to include the thickness noise, the loading noise, and the flow noise generated from the shock waves and the tip vortices. The computation was performed with compressible three-dimensional Euler's equations and Navier-Stokes equations. The high speed impulsive noise was predicted and validated according to the permeable surface locations. It is confirmed that the noise source caused by shock waves generated on the blade surface is a dominant factor in the far-field noise prediction.

Blade shape optimization of centrifugal fan for improving performance and reducing aerodynamic noise of clothes dryer (의류 건조기 성능 향상과 공력소음 저감을 위한 원심팬의 날개 형상 최적화)

  • Choi, Jinho;Ryu, Seo-Yoon;Cheong, Cheolung;Kim, Min-kyu;Lee, Kwangho
    • The Journal of the Acoustical Society of Korea
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    • v.38 no.3
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    • pp.321-327
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    • 2019
  • The purpose of this study is paper is to improve the flow performance and to reduce the aerodynamic noise of air discharge system consisting of a centrifugal fan, ducts and a housing for the clothes dryer. Using computational fluid dynamics and acoustic analogy based on FW-H (Ffowcs-Williams and Hawkings) Eq., air flow field and acoustic fields of the air discharge system are investigated. To optimize aerodynamic performance and aerodynamic noise, the response surface method is employed. The two factors central composite design using the inflow and outflow angles of fan blades is adopted. The devised optimum design shows the reduction of turbulent kinetic energy in the ducts and the housing of the system, and as a result, the improved flow rate and reduce noise is confirmed. Finally, the experment using the proto-type manufactured usign the optimum design shows the increase of flow rate by 4.2 %.

Design of Low Noise Airfoil for Use on Small Wind Turbines (소형 풍력발전기 소음 저감을 위한 익형 설계 연구)

  • Kim, Tae-Hyung;Lee, Seung-Min;Kim, Ho-Geon;Lee, Soo-Gab
    • 한국신재생에너지학회:학술대회논문집
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    • pp.465-465
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    • 2009
  • Wind power is one of the most reliable renewable energy sources and the installed wind turbine capacities are increasing radically every year. Although wind power has been favored by the public in general, the problem with the impact of wind turbine noise on people living in the vicinity of the turbines has been increased. Low noise wind turbine design is becoming more important as noise is spreading more adverse effect of wind turbine to public. This paper demonstrates the design of 10 kW class wind turbines, each of three blades, a rotor diameter 6.4m, a rated rotating speed 200 rpm and a rated wind speed 10 m/s. The optimized airfoil is dedicated for the 75% spanwise position because the dominant source of a wind turbine blade has been known as trailing edge noise from the outer 25% of the blade. Numerical computations are performed for incompressible flow and for Mach number at 0.145 and for Reynolds numbers at $1.02{\times}10^6$ with a lift performance, which is resistant to surface contamination and turbulence intensity. The objective in the low design process is to reduce noise emission, while sustaining high aerodynamic efficiency. Dominant broadband noise sources are predicted by semi-empirical formulas composed of the groundwork by Brooks et al. and Lowson associated with typical wind turbine operation conditions. During the airfoil redesign process, the aerodynamic performance is analyzed to minimize the wind turbine power loss. The results obtained from the design process show that the design method is capable of designing airfoils with reduced noise using a commercial 10 kW class wind turbine blade airfoil as a basis. The new optimized airfoil clearly indicates reduction of total SPL about 3 dB and higher aerodynamic performance.

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A Study on the Identification of Aeroacoustic Noise and Noise Reduction for a Vacuum Cleaner (청소기의 공력소음 특성 파악 및 저소음화에 관한 연구)

  • 전완호;백승조;김창준
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.13 no.6
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    • pp.460-466
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    • 2003
  • The aeroacoustic characteristics and noise reduction method of a centrifugal fan for a bagless vacuum cleaner were studied. The major noise source of vacuum cleaner is the centrifugal fan. The impeller of the fan rotates over 30000 rpm and generates very high-level piercing noise. It was found that the dominant noise source of the fan is generated from the aerodynamic interaction between the highly rotating impeller and stationary diffuser. In order to reduce the high tonal sound generated from the aerodynamic interaction between the impeller and diffuser, tapered impeller was carefully designed and tested. The trailing edge of the tapered impeller was inclined and this reduces the flow interactions between the rotating impeller and the stationary diffuser because of some phase shift. The static efficiency of the new impeller is slightly lower than the conventional one. The overall SPL is reduced about 3.6 dBA. The SPL of blade passing frequency(BPF) is reduced about 6 dBA and the $2^{nd}$ BPF is reduced about 20 dBA. The vacuum cleaner with the tapered impeller has lower noise level than that of the previous impeller and the strong tonal sound was dramatically reduced.