• Title/Summary/Keyword: Aerodynamic Data

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Analysis of Propeller-WIG Interaction and Performance in Potential Flow (포텐셜 유동에 의한 프로펠러-WIG선의 상호작용 및 성능해석)

  • H.H. Chun;M.G. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.38 no.4
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    • pp.11-22
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    • 2001
  • The interaction between forward mounted propeller and wing in ground effect, and its aerodynamic performance are analyzed by potential flow approximation. A Vortex Lattice Method(VLM) for the propeller analysis and a potential based panel method for the WIG are used together with an image method by assuming the free surface as a rigid wall. The interaction of propeller and wing in the proximity of the ground is taken into account by an iterative procedure where the boundary conditions are satisfied with the given convergence criteria. The program developed is first checked by comparing its numerical results with the experimental data and other numerical results for the propeller MP101-rudder MR21 system. Then, the propeller-WIG interaction and its performance versus ground clearance are investigated by changing parameters such as propeller position, diameter and speed of revolution. It is shown that the forward mounted propeller increases the lift forces of the wing and also enhances the height stability, depending on the design parameter. Therefore, the appropriate selection of the design parameter such as propeller diameter, revolution, the longitudinal and vertical position of propeller is necessary.

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Effects of Reduced Ambient PM10 Levels on the Health of Children in Lower-income Families (대기질 개선과 저소득계층 어린이 건강보호 효과)

  • Bae, Hyun-Joo
    • Journal of Environmental Health Sciences
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    • v.36 no.3
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    • pp.182-190
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    • 2010
  • We examined the association of particulate matter with an aerodynamic diameter < $10\;{\mu}m$ ($PM_{10}$) with asthma-related hospitalization, stratified by socioeconomic status (SES), among children less than 15 years of age in Seoul, Korea, between 2003 and 2005. In addition, we estimated the reduction in the number of asthma-related hospitalizations that would result from implementing the World Health Organization (WHO) guideline. SES was defined based on data concerning health insurance premium grades, and grouped into two levels: lower-income group and control group. The lower-income group was classified as having an accumulated income which did not exceed the 50th percentile of the median income. Time-series analysis was performed to evaluate the association between $PM_{10}$ and asthma-related hospitalization. The Environmental Benefits Mapping and Analysis Program was used to analyze the impact on children's health. Based upon an increase of $10\;{\mu}g/m^3$ of $PM_{10}$, the asthma-related hospitalization risk for the lower-income group was increased by 1.78% (95% confidence intervals (CI) = 0.79-2.78%), while the risk for the control group was increased by 0.83% (95% CI = 0.34-1.32%). Attaining the WHO guideline, relative to the concentration in 2007, would result in a reduction in asthma-related hospitalizations of 18 cases per 100,000 of the children population in the lower-income group, and 7 cases in the control group. The health benefits of improved air quality for children in the lower-income group were thus 2.5 times greater than for children in the control group. Our results show that the lower-income group is disproportionately burdened with asthma-related hospitalization arising from air pollution. Therefore, biologically- and socioeconomically-disadvantaged populations should be considered in public health interventions in order to protect the children's health.

Development of an Analysis Program for Small Horizontal Wind Turbines Considering Side Furling and Optimal Torque Scheduling (사이드 펄링과 최적 토크스케줄을 고려한 소형 풍력터빈 해석 프로그램 개발)

  • Jang, Hyeon-Mu;Kim, Dong-Myeong;Paek, In-Su
    • Journal of the Korean Solar Energy Society
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    • v.38 no.2
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    • pp.15-31
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    • 2018
  • A program to design a small capacity wind turbine blade is proposed in this study. The program is based on a matlab GUI environment and designed to perform blade design based on the blade element momentum theory. The program is different from other simulation tools available in a point that it can analyze the side-furling power regulation mechanism and also has an algorithm to find out optimal torque schedule above the rated wind speed region. The side-furling power regulation is used for small-capacity horizontal axis wind turbines because they cannot use active pitch control due to high cost which is commonly used for large-capacity wind turbine. Also, the torque schedule above the rated wind speed region should be different from that of the large capacity wind turbines because active pitching is not used. The program developed in this study was validated with the results with FAST which is the only program that can analyze the performance of side-furled wind turbines. For the validation a commercial 10 kW wind turbine data which is available in the literature was used. From the validation, it was found that the performance prediction from the proposed simple program is close to those from FAST. It was also found that the optimal torque scheduling from the proposed program was found to increase the turbine power substantially. Further experimental validation will be performed as a future work.

Design of Instrumented Pod for Flight Aeroacoustic Environment (비행 공력음향 환경 측정을 위한 계측포드 설계)

  • Jun, Oo-Chul;Kim, Sang-Yong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.6
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    • pp.536-541
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    • 2012
  • An instrumented pod has been developed to measure the aeroacoustic environment as well as the conventional data such as load, vibration, and aerodynamic heating of fighters during flight tests, confirming to the recently developed external pod design for fighters. This study presents the development of the measurement system in detail, being the first indigenous effort in its kind. The pod was designed to meet the requirements of the MIL-HDBK-1763 and MIL-STD-810 Method 515, which are the base to determine the locations and range of sensors. The Endevco 8510B-2 was selected as the sensor to withstand the harsh environment during the flight tests. In order to assess the integrity of the fabricated pod design, a ground run-up test of a KF-16 has been conducted with the pod installed at Station 5. The test results show that the system works well but the sound level exceeds the predetermined sensor range. The sensor range has been readjusted for flight test performed later.

Unsteady Aerodynamic Analysis for Helicopter Rotor in Hovering and Forward Flight Using Overlapped Grid (중첩 격자를 이용한 제자리 및 전진 비행하는 헬리콥터 로터의 비정상 공력해석)

  • Im, Dong-Kyun;Wie, Seong-Yong;Kim, Eu-Gene;Kwon, Jang-Hyuk;Lee, Duck-Joo;Park, Soo-Hyung;Chung, Ki-Hoon;Kim, Seung-Bum
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.3
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    • pp.215-223
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    • 2009
  • In this paper, the helicopter aerodynamics is simulated in hovering and forward flight. Also, an overlapped grid technique is applied in this simulation to consider the blade motion and moving effects. The Caradonna & Tung's rotor blade was selected to analyze the unsteady aerodynamics in hovering and non-lift forward flight. Also, the AH-1G rotor blade was selected in forward flight. In forward flight case, the numerical trim was applied to determine the cyclic pitching angles using Newton-Raphson method, and the numerical results were in good agreement with experimental data, especially, the BVI effects were well simulated in advancing side in comparison other numerical results. The governing equation is a three dimensional unsteady Euler equation, and the Riemann invariants condition is used for inflow and outflow at the boundary.

Measurement of Aerodynamic Heating over a Protuberance in Hypersonic Flow of Mach 7 (Mach 7 극초음속 유동 내의 돌출물 공력가열 계측)

  • Lee, Hyoung-Jin;Lee, Bok-Jik;Jeung, In-Seuck;Kim, Seong-Lyong;Kim, In-Sun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.6
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    • pp.562-570
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    • 2009
  • An Experimental study was conducted on the flow characteristics and interference heating caused by a two-dimensional object protruding from a flat plate using a blow-down type of hypersonic wind tunnel. Inflow condition was a free-stream Mach number of 7.0 and a unit Reynolds number of $2.0{\times}10^6/m$. Experimental conditions were varied with three heights of protuberance for two flat plate models which have different lengths. Experimental data were obtained from Schlieren visualization images and heat flux measurements. Also, this paper suggests hypersonic experimental techniques such as boundary-layer detection method in detail. A Large separation region was observed in front of the protuberance and that region was very sensitive to the height of protuberance and the length of the flat plate. For only the highest protuberance, a severe jump of heat flux was observed at the top station among the measuring points. Measured heat flux is large when the height of protuberance is large and the length of flat plate is long.

Aerodynamic Approaches for the Predition of Spread the HPAI (High Pathogenic Avian Influenza) on Aerosol (고병원성 조류인플루엔자 (HPAI)의 에어로졸을 통한 공기 전파 예측을 위한 공기유동학적 확산 모델 연구)

  • Seo, Il-Hwan;Lee, In-Bok;Moon, Oun-Kyung;Hong, Se-Woon;Hwnag, Hyun-Seob;Bitog, J.P.;Kwon, Kyeong-Seok;Kim, Ki-Youn
    • Journal of The Korean Society of Agricultural Engineers
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    • v.53 no.1
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    • pp.29-36
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    • 2011
  • HPAI (High pathogenic avian influenza) which is a disease legally designated as an epidemic generally shows rapid spread of disease resulting in high mortality rate as well as severe economic damages. Because Korea is contiguous with China and southeast Asia where HPAI have occurred frequently, there is a high risk for HPAI outbreak. A prompt treatment against epidemics is most important for prevention of disease spread. The spread of HPAI should be considered by both direct and indirect contact as well as various spread factors including airborne spread. There are high risk of rapid propagation of HPAI flowing through the air because of collective farms mostly in Korea. Field experiments for the mechanism of disease spread have limitations such as unstable weather condition and difficulties in maintaining experimental conditions. In this study, therefore, computational fluid dynamics which has been actively used for mass transfer modeling were adapted. Korea has complex terrains and many livestock farms are located in the mountain regions. GIS numerical map was used to estimate spreads of virus attached aerosol by means of designing three dimensional complicated geometry including farm location, road network, related facilities. This can be used as back data in order to take preventive measures against HPAI occurrence and spread.

Effects of Didecyldimethylammonium Chloride on Sprague-Dawley Rats after Two Weeks of Inhalation Exposure

  • Lim, Cheol-Hong;Chung, Yong-Hyun
    • Toxicological Research
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    • v.30 no.3
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    • pp.205-210
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    • 2014
  • Didecyldimethylammonium chloride (DDAC) is used for various purposes, such as a fungicide for coolants, an antiseptic for wood, and disinfectant for cleaning. Despite the increasing likelihood of DDAC inhalation, available data on its toxicity from inhalation are scarce. Therefore, this study was aimed at confirming the toxicity of DDAC after inhalation exposure for 2 wk. Male Sprague-Dawley rats were exposed to approximately $0.15mg/m^3$, $0.6mg/m^3$, and $3.6mg/m^3$ DDAC aerosols in whole-body exposure chambers. After DDAC exposure for 2 wk, effects of DDAC on body weight, blood, bronchoalveolar lavage (BAL), and the lungs were verified. The mass median aerodynamic diameter of DDAC aerosols was $1.86{\mu}m$ and the geometric standard deviation was 2.75. The concentrations of DDAC aerosols for the low, medium, and high groups were $0.15{\pm}0.15mg/m^3$, $0.58{\pm}0.40mg/m^3$, and $3.63{\pm}1.56mg/m^3$, respectively. Body weight gain was significantly influenced by DDAC exposure. In the high group, a body weight decrease of 2.6 g was observed, whereas a 25.8 g increase was observed in the normal control group after the first 3 days. The low and medium groups showed 23.3 g and 20.4 g increases, respectively, after the first 3 days. Decreases in body weight were recovered during the next 4 days. In contrast, no changes were noted in hematological and blood biochemistry parameters after DDAC exposure. Furthermore, only mild effects were observed on bronchoalveolar cell differentiation counts and cell damage parameters in the BAL fluids of the medium and high groups. Although inflammatory cell infiltration and interstitial pneumonia were partially observed, fibrosis was not found in the lungs of the medium and high groups. In conclusion, body weight gain and the lungs were mainly affected by DDAC exposure. The no-observed-adverse-effect level (NOAEL) for DDAC was determined as $0.15mg/m^3$.

Customized Aerodynamic Simulation Framework for Indoor HVAC Using Open-Source Libraries (공개 라이브러리 기반 실내 공조 맞춤형 전산모사 시스템 개발)

  • Sohn, Ilyoup;Roh, Hyunseok;Kim, Jaesung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.2
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    • pp.135-143
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    • 2017
  • A customized CFD simulator to perform thermo-fluid dynamic simulations of an HVAC for an indoor space is presented. This simulation system has been developed for engineers studying architectural engineering, as the HVAC mechanical systems used in housings and buildings. Hence, all functions and options are so designed to be suitable that they are suitable for non-CFD experts as well as CFD engineers. A Computational mesh is generated by open-source libraries, FEMM (Finite Element Method Magnetics), and OpenFOAM. Once the boundary conditions are set, the fluid dynamic calculations are performed using the OpenFOAM solver. Numerical results are validated by comparing them with the experimental data for a simple indoor air flow case. In this paper, an entirely new calculation process is introduced, and the flow simulation results for a sample office room are also discussed.

9-DOF Modeling and Turning Flight Simulation Evaluation for Parachute (9-DOF 낙하산 모델링 및 선회비행 시뮬레이션 검증)

  • Lee, Sang-Jong;Min, Byoung-Mun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.9
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    • pp.688-693
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    • 2016
  • This paper describes the parachute dynamics modeling and simulation results for the development of training simulator of a HALO (High Altitude Low Opening) parachute, which is currently in use for military purposes. The target parachute is a rectangular shaped parafoil and its dynamic model is derived based on the real geometry data as the 9-DOF nonlinear equations of dynamics. The simulation was conducted through the moment of inertia and its aerodynamic derivatives to reflect the real characteristics based on the MATLAB/Simulink. In particular, its modeling includes the typical characteristics of the added mass and moment of inertia, which is shown in the strong effects in Lighter-Than-Air(LTA) flight vehicle. The proposed dynamic modeling was evaluated through the simulation under the spiral turning flight conditions of the asymmetric control inputs and compared with the performance index in the target parachute manual.