• Title, Summary, Keyword: Aerodynamic Noise

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Development of aerodynamic noise prediction technique for high efficiency and low noise design of unmanned aerial vehicle propeller (멀티로터형 무인항공기 프로펠러의 고효율 및 저소음 설계를 위한 공력 소음 예측 기법 개발)

  • Gwak, Doo Young;Lee, Soogab
    • The Journal of the Acoustical Society of Korea
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    • v.36 no.2
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    • pp.89-99
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    • 2017
  • Multi-rotor type UAV (Unmanned Aerial Vehicle)s are expanding their applications not only for military purposes but also for private industries such as aerial photography and unmanned delivery vehicles. For wider use of unmanned aerial vehicles, studies should be carried out to improve aerodynamic efficiency and reduce noise of propellers, which can be achieved based on techniques of predicting aerodynamic performance and noise in a given environment. In this study, aerodynamic and noise prediction techniques were developed for a small unmanned aerial vehicle propeller, and it was verified by comparing it with actual measurement results. Thrust and torque due to the change of r/min and the frequency spectral prediction at a given position secured the reliability of the prediction method, which provides a basis for the shape design of the propeller.

Analysis of Interior Noise of KTX in Tunnel with Concreted Track (콘크리트 궤도 터널 내 KTX 차량의 실내소음 특성 분석)

  • Kim, Jae-Chul;Lee, Chan-Woo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.11
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    • pp.1037-1042
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    • 2007
  • KTX trains show a high interior noise level in tunnel with concreted track at 300 km/h. Generally, the concreted track has higher sound emissions compared with ballasted track due to the reduced absorption and the major sources of interior noise for KTX are known as the aerodynamic noise and rolling noise. Therefore, It is necessary to find out noise source and noise components to affect interior noise in tunnel with concreted track. In this study, we measure the noise and vibration inside KTX in tunnel in order to find the cause of the interior noise of KTX. The analysis results show that the interior noise of KTX in tunnel with concreted track is increased sharply by a low frequency below 80 Hz. We know that the low frequency noise inside KTX in tunnel with concreted track is generated at the natural frequency of carbody by aerodynamic noise outside gangway and rolling noise. In order to reduce the noise level at 80 Hz, modification of mud-flap length between carbodys is suggested and the effect of noise reduction is examined in tunnel with concreted track.

Evaluation of Design Program of Low-Noise Axial Fan (축류형 송풍기 저소음 설계 프로그램의 개발 및 평가)

  • 김기황;박준철;김진화;이승배
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.967-972
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    • 2001
  • An axial fan design code, called iDesignFan$^{TM}$, was developed. In this code, three major loss models were used to predicted the aerodynamic performance of a fan. The overall sound pressure level, predicted from steady blade loading, is also used as an input parameter from the third loop of the designing process to acquire most silent fan for the given aerodynamic performance parameters. With this kind of inverse design concept used in this code, the period of designing a fan, which has given aerodynamic performance with minimal acoustic noise, is significantly shortened. The experimental results of a prototype fan, designed by this code, showed that aerodynamic and acoustic performance of an axial fan is reasonably well predicted. Thus, one can design/develop an axial fan in a short time by using the code.e.

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The Effect of Scaling of Owl's Flight Feather on Aerodynamic Noise at Inter-coach Space of High Speed Trains based on Biomimetic Analogy

  • Han, Jae-Hyun;Kim, Tae-Min;Kim, Jung-Soo
    • International Journal of Railway
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    • v.4 no.4
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    • pp.109-115
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    • 2011
  • An analysis and design method for reducing aerodynamic noise in high-speed trains based on biomimetics of noiseless flight of owl is proposed. Five factors related to the morphology of the flight feather have been selected, and the candidate optimal shape of the flight feather is determined. The turbulent flow field analysis demonstrates that the optimal shape leads to diminished vortex formation by causing separation of the flow as well as allowing the fluid to climb up along the surface of the flight feather. To determine the effect of scaling of the owl's flight feather on the noise reduction, a two-fold and a four-fold scaled up model of the feather are constructed, and the numerical simulations are carried out to obtain the aerodynamic noise levels for each scale. Original model is found to reduce the noise level by 10 dBA, while two-fold increase in length dimensions reduces the noise by 12 dBA. Validation of numerical solution using wind tunnel experimental measurements is presented as well.

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A Computerized Design System of the Axial Fan Considering Performance and Noise Characteristics (성능 및 소음특성을 고려한 축류 팬 설계의 전산 체계)

  • Lee, Chan;Kil, Hyun-Gwon
    • The KSFM Journal of Fluid Machinery
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    • v.13 no.2
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    • pp.48-53
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    • 2010
  • A computerized design system of axial fan is developed for constructing 3-D blade geometry and predicting both aerodynamic performance and noise. The aerodynamic blading design of fan is conducted by blade angle distribution, camber line determination, airfoil thickness distribution and blade element stacking along spanwise distance. The internal flow and the aerodynamic performance of designed fan are predicted by the through-flow modeling technique with flow deviation and pressure loss correlations. Based on the predicted internal flow field and performance data, fan noise is predicted by two models for discrete frequency and broadband noise sources. The present predictions of the flow distribution, the performance and the noise level of actual fans are well agreed with measurement results.

Efficient Flutter Analysis for Aircraft with Various Analysis Conditions (다양한 해석조건을 갖는 항공기에 대한 효율적인 플러터 해석)

  • Lee, Sang-Wook;Kim, Tae-Uk;Hwang, In-Hee;Paek, Seung-Kil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.49-52
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    • 2005
  • Flutter analysis procedure can be divided into two steps such as the computation of generalized mass, stiffness, and unsteady aerodynamic matrices and the calculation of major vibration modes frequency and damping values at each flight speed by solving the complex eigenvalue problem. In aircraft flutter analyses, most of the time is spent in the process of computing the unsteady aerodynamic matrices at each Mach-reduced frequency pairs defined. In this study, the method has been presented for computation and extraction of unsteady aerodynamic matrix portions dependent only on aerodynamic model using DMAP ALTER in MSC/NASTRAN SOL 145. In addition, efficient flutter analysis method has been suggested by computing and utilizing the unsteady generalized aerodynamic matrices for each analysis condition using the unsteady aerodynamic matrix portions extracted above.

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Design Method of the Sirocco Fan Considering Aeroacoustic Performance Characteristics (공력음향학적 특성을 고려한 시로코 팬의 설계 방법)

  • Lee, Chan
    • The KSFM Journal of Fluid Machinery
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    • v.13 no.2
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    • pp.59-64
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    • 2010
  • A design method of Sirocco fan is developed for constructing 3-D impeller and scroll geometries, and for predicting both the aerodynamic performance and the noise characteristics of the designed fan. The aerodynamic blading design of fan is conducted by blade angle, camber line determinations and airfoil thickness distribution, and then the scroll geometry of fan is designed by using logarithmic spiral. The aerodynamic performance of designed fan is predicted by the meanline analysis with flow blockage, slip and pressure loss correlations. Based on the predicted performance data, fan noise is predicted by two models for cutoff frequency and broadband noise sources. The present predictions for the performance and the noise level of actual fans are well agreed with measurement results.

A Numerical Study on Aerodynamic Noise Characteristics of the Tandem Cylinders using DES and FW-H Acoustic Analogy (DES와 FW-H 음향상사법을 이용한 탠덤 실린더의 공력소음 특성 연구)

  • Kim, Manshik;Lee, Youn Kyu
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.11
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    • pp.883-891
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    • 2018
  • In this paper, aerodynamic noise simulation was conducted using DES (Detached Eddy Simulation) and FW-H (Ffowcs Williams and Hawkings) acoustic analogy for the tandem cylinders which have configuration similar to a landing gear of airplanes. Numerical simulation for the tandem cylinders whose centers are 3.7D apart was carried out and results were compared with the measured data such as flow characteristics, pressure coefficients on the cylinder surfaces and far-field noise characteristics. It was confirmed that periodically shedded vortices released at the upstream cylinder and impinged on the downstream cylinder surface are major sources of aerodynamic noise. After verifying the computational method of using DES and FW-H acoustic analogy for predicting aerodynamic noise of tandem cylinders, additional simulation was conducted to examine the effect of attaching a splitter plate at the rear of the upstream cylinder. It was confirmed that the noise level in specific frequency band decreased significantly because the splitter plate changed the vortex shedding features and reduced dipole noise source.

DESIGN FOR AERODYNAMIC NOISE REDUCTION OF RAILWAY TRACTION MOTOR USING LBM (격자볼츠만기법을 이용한 전동차용 견인전동기 공력소음 저감 설계)

  • Kim, J.H.;Ki, H.C.;Byun, S.J.;Rho, J.H.
    • Journal of computational fluids engineering
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    • v.22 no.1
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    • pp.103-109
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    • 2017
  • The aerodynamic noise reduction of railway traction motor is required to satisfy new enhanced Korean noise regulations for a train. This paper is the study result on a noise reduction of a railway traction motor using Lattice Boltzmann Method(LBM). To verify the reliability of numerical analysis, the noise performance of the base model evaluated using LBM, and calculated result was compared with the experimental data. In addition, main noise sources were selected to design parameters through analyzing the flow field of the base model. Based on the noise sources analysis result, a design improvement model of traction motor for this study was derived to reduce the noise. The performance of a design improvement model was evaluated by applying a validated numerical scheme. As a result, it was confirmed that the noise was reduced due to the suppression of the internal turbulent flow components.

Nose Shape Optimization of the High-speed Train to Reduce the Aerodynamic drag and Micro-pressure Wave (공기저항과 미기압파 저감을 위한 고속전철 전두부형상의 최적화설계)

  • Kwon, Hyeok-Bin;Kim, Yu-Shin;Lee, Dong-Ho;Kim, Moon-Sang
    • Proceedings of the KSME Conference
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    • pp.373-379
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    • 2001
  • When a train runs into a tunnel at high-speed, aerodynamic drag suddenly increases and the booming noise is generated at the exit of tunnel. The noise shape is very important to reduce the aerodynamic drag in tunnel as well as on open ground, and the micro-pressure wave that is a source of booming noise is dependent on nose shape, especially on area distribution. In this study, the nose shape has been optimized employing the response surface methodology and the axi-symmetric compressible Navier-Stokes equations. The optimal designs have been executed imposing various conditions of the aerodynamic drag and the micro-pressure wave on object functions. The results show that the multi-objective design was successful to decrease micro-pressure wave and aerodynamic drag of trains.

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