• Title, Summary, Keyword: aerodynamic

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Aerodynamic Heating Test of Payload Fairing of KSLV-I (KSLV-I 페어링 공력 가열 시험)

  • Choi, Sang-Ho;Kim, Seong-Lyong;Kim, In-Sun
    • 한국전산유체공학회:학술대회논문집
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    • pp.448-451
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    • 2008
  • KARI is developing a satellite launch vehicle that is called KSLV(Korea Space Launch Vehicle)-I. During the flight, launch vehicles are exposed to aerodynamic heating conditions while flying at high Mach numbers in the atmosphere. KARI constructed Aerodynamic Thermal Simulation Facility to simulate aerodynamic heating on the ground. ATSF is a facility that can simulate given temperature profile using about 4,000 halogen heaters on fairing model. Aerodynamic heating profile is got from result of thermal analysis using MINIVER, Thermal Desktop, and SINDA/FLUINT. Aerodynamic heating test of fairing of KSLV-I was done using engineering model of payload fairing and Aerodynamic Thermal Simulation Facility. It was found that thermal analytic results show good agreement with aerodynamic heating test results within 6$^{\circ}$C at fairing inner surface. Also it was confirmed that maximum temperature of fairing nose-cone inner surface during flight is lower than allowable temperature limit.

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Korean Adult Normative Data for the KayPENTAX Phonatory Aerodynamic System Model 6600 (KayPENTAX Phonatory Aerodynamic System Model 6600을 이용한 한국 성인의 공기역학적 변수들의 정상치)

  • Kim, Jaeock
    • Phonetics and Speech Sciences
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    • v.6 no.1
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    • pp.105-117
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    • 2014
  • The purpose of this study was to (1) establish a Korean adult normative database for phonatory aerodynamic measures obtained with the KayPENTAX Phonatory Aerodynamic System (PAS) Model 6600, (2) investigate the intra-subject reliability of these measures across three testing sessions, and (3) examine the effect of gender on those measures. 170 healthy normal speakers (70 men and 100 women) between the ages 18 and 49 years participated in the study. The PAS protocol of maximum phonation and voicing efficiency were conducted and 25 measures were obtained. All aerodynamic measures taken in this study demonstrated high intra-subject reliability in clinical aspect. There were no significant effect of gender in the measures related to sound pressure and subglottal pressure. However, significant differences for gender were found for phonation time, airflow rate, expiratory volume, aerodynamic power, SPL range, pitch range, mean pitch, aerodynamic resistance, and aerodynamic efficiency. Clinicians should be aware of significant gender effects in some aerodynamic parameters when interpreting the data obtained from PAS.

Aerodynamic Design Techniques in The Launch Vehicle (발사체 개발에서의 공력설계 기법)

  • Ahn, Chang-Soo;Sun, Chul;Kang, Kyoung-Tai
    • 유체기계공업학회:학술대회논문집
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    • pp.41-44
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    • 2006
  • In the field of launch vehicle development, aerodynamic design means an overall management about external appearances. At least, related to outer figures of the launch vehicle, aerodynamic design has the initiative activities. For that reason, in this report, aerodynamic design techniques and application methods will be introduced.

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Experimental and numerical studies of aerodynamic forces on vehicles and bridges

  • Han, Yan;Hu, Jiexuan;Cai, C.S.;Chen, Zhengqing;Li, Chunguang
    • Wind and Structures
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    • v.17 no.2
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    • pp.163-184
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    • 2013
  • An accurate identification of the aerodynamic characteristics of vehicles and the bridge is the premise for the coupled vibration analysis of a wind-vehicle-bridge system. At present, the interaction of aerodynamic forces between the road vehicles and bridge is ignored in most previous studies. In the present study, an experimental setup was developed to measure the aerodynamic characteristics of vehicles and the bridge for different cases in a wind tunnel considering the aerodynamic interference. The influence of the wind turbulence, the wind speed, the vehicle interference, and the vehicle position on the aerodynamic coefficients of vehicles, and the influence of vehicles on the static coefficients of the bridge were investigated, based on the experimental results. The variations in the aerodynamic characteristics of vehicles and the bridge were studied and the measured results were validated according to the results of surface pressure measurements on the vehicle and the bridge. The measured results were further validated by comparing the measured results with values derived numerically. The measured results showed that the wind turbulence, the vehicle interference, and the vehicle position significantly affected the aerodynamic coefficients of vehicles. However, the influence of the wind speed on the aerodynamic coefficients of the studied vehicle is small. The static coefficients of the bridge were also significantly influenced by the presence of vehicles.

An Investigation on Nonlinear Characteristics of Aerodynamic Torque for Variable-Speed Variable-Pitch Wind Turbine (가변속도-가변피치 풍력터빈의 공기역학적 토크의 비선형 특성에 관한 고찰)

  • Lim, Chae-Wook
    • The KSFM Journal of Fluid Machinery
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    • v.14 no.2
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    • pp.29-34
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    • 2011
  • Aerodynamic torque of wind turbine is highly nonlinear due to the nonlinear interactions between wind and blade. The aerodynamic nonlinearity is represented by nonlinear power and torque coefficients which are functions of wind speed, rotational speed of rotor, and pitch angle of blade. It is essential from the viewpoint of understanding and analysis of dynamic characteristics for wind turbine to linearize the aerodynamic torque and define aerodynamic nonlinear parameters as derivatives of aerodynamic torque with respect to the three parameters. In this paper, a linearization method of the aerodynamic torque from power coefficient is presented through differentiating it by the three parameters. And steady-state values of three aerodynamic nonlinear parameters according to wind speed are obtained and their nonlinear characteristics are investigated.

Aerodynamic Heating Test of Fairing Nose-Cone (페어링 노즈콘에 대한 공력가열 시험)

  • Choi, Sang-Ho;Kim, Seong-Lyong;Kim, In-Sun
    • Proceedings of the KSME Conference
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    • pp.2534-2539
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    • 2007
  • Launch vehicles are exposed to aerodynamic heating conditions while flying at high Mach numbers in the atmosphere. In this study aerodynamic heating test for fairing nose-cone was done using ATSF(Aerodynamic Thermal Simulation Facility) and Engineering Model for fairing. ATSF is a facility that can simulate given temperature profile using about 4,000 halogen heaters on fairing model. Aerodynamic heating profile is got from result of thermal analysis using MINIVER, Thermal Desktop and SINDA/FLUINT. After aerodynamic heat test, it is found that initial temperature of fairing inner surface and thickness of BMS has important effects on temperature of fairing inner surface. Also it is confirmed that maximum temperature of fairing nose-cone inner surface during flight is lower than allowable temperature limit. Later, thermal correlation between thermal analysis and experimental results will be done using aerodynamic heating test result

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Study of Flight Simulation using Real-Time Aerodynamic Model (실시간 공력모델을 이용한 비행 시뮬레이션 연구)

  • Lee, Chang Ho;Park, Young Min;Choi, Hyoung Sik
    • Journal of Aerospace System Engineering
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    • v.9 no.4
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    • pp.49-54
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    • 2015
  • Accurate aerodynamic data is required for the flight simulation or control logic design of aircraft. The aerodynamic look-up table has been used widely to provide aerodynamic forces and moments for given flight conditions. In this paper, we replace the aerodynamic look-up table with real-time aerodynamic model which calculates aerodynamic forces and moments of quasi-steady flow directly for given flight conditions and control surface deflections. Flight simulations are conducted for the low-speed small UAV using real-time aerodynamic model, and responses of the UAV are predicted successfully for inputs of control surfaces.

Analysis of Aerodynamic Noise at Inter-coach Space of High Speed Trains

  • Kim, Tae-Min;Kim, Jung-Soo
    • International Journal of Railway
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    • v.7 no.4
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    • pp.100-108
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    • 2014
  • A numerical analysis method for predicting aerodynamic noise at inter-coach space of high-speed trains, validated by wind-tunnel experiments for limited speed range, is proposed. The wind-tunnel testing measurements of the train aerodynamic sound pressure level for the new generation Korean high-speed train have suggested that the inter-coach space aerodynamic noise varies approximately to the 7.7th power of the train speed. The observed high sensitivity serves as a motivation for the present investigation on elucidating the characteristics of noise emission at inter-coach space. As train speed increases, the effect of turbulent flows and vortex shedding is amplified, with concomitant increase in the aerodynamic noise. The turbulent flow field analysis demonstrates that vortex formation indeed causes generation of aerodynamic sound. For validation, numerical simulation and wind tunnel measurements are performed under identical conditions. The results show close correlation between the numerically derived and measured values, and with some adjustment, the results are found to be in good agreement. Thus validated, the numerical analysis procedure is applied to predict the aerodynamic noise level at inter-coach space. As the train gains speed, numerical simulation predicts increase in the overall aerodynamic sound emission level accompanied by an upward shift in the main frequency components of the sound. A contour mapping of the aerodynamic sound for the region enclosing the inter-coach space is presented.

New estimation methodology of six complex aerodynamic admittance functions

  • Han, Y.;Chen, Z.Q.;Hua, X.G.
    • Wind and Structures
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    • v.13 no.3
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    • pp.293-307
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    • 2010
  • This paper describes a new method for the estimation of six complex aerodynamic admittance functions. The aerodynamic admittance functions relate buffeting forces to the incoming wind turbulent components, of which the estimation accuracy affects the prediction accuracy of the buffeting response of long-span bridges. There should be two aerodynamic admittance functions corresponding to the longitudinal and vertical turbulent components, respectively, for each gust buffeting force. Therefore, there are six aerodynamic admittance functions in all for the three buffeting forces. Sears function is a complex theoretical expression for the aerodynamic admittance function for a thin airfoil. Similarly, the aerodynamic admittance functions for a bridge deck should also be complex functions. This paper presents a separated frequency-by-frequency method for estimating the six complex aerodynamic admittance functions. A new experimental methodology using an active turbulence generator is developed to measure simultaneously all the six complex aerodynamic admittance functions. Wind tunnel tests of a thin plate model and a streamlined bridge section model are conducted in turbulent flow. The six complex aerodynamic admittance functions, determined by the developed methodology are compared with the Sears functions and Davenport's formula.

Study on aerodynamic shape optimization of tall buildings using architectural modifications in order to reduce wake region

  • Daemei, Abdollah Baghaei;Eghbali, Seyed Rahman
    • Wind and Structures
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    • v.29 no.2
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    • pp.139-147
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    • 2019
  • One of the most important factors in tall buildings design in urban spaces is wind. The present study aims to investigate the aerodynamic behavior in the square and triangular footprint forms through aerodynamic modifications including rounded corners, chamfered corners and recessed corners in order to reduce the length of tall buildings wake region. The method used was similar to wind tunnel numerical simulation conducted on 16 building models through Autodesk Flow Design 2014 software. The findings revealed that in order to design tall 50 story buildings with a height of about 150 meters, the model in triangular footprint with aerodynamic modification of chamfered corner facing wind direction came out to have the best aerodynamic behavior comparing the other models. In comparison to the related reference model (i.e., the triangular footprint with sharp corners and no aerodynamic modification), it could reduce the length of the wake region about 50% in general. Also, the model with square footprint and aerodynamic modification of chamfered corner with the corner facing the wind could present favorable aerodynamic behavior comparing the other models of the same cluster. In comparison to the related reference model (i.e., the square footprint with sharp corners and no aerodynamic modification), it could decrease the wake region up to 30% lengthwise.