• 오토저널
• /
• 제5권2호
• /
• pp.56-63
• /
• 1983

The aerodynamic characteristics of the most popular car (PONY 2) produced in Korea have been experimentally investigated by Seoul National University's wind tunnel. The model (PONY 2) chosen for the wind tunnel was a 1/5 scale of the original car without simulated underbody, cooling air flow and accessories. The measured aerodynamic drag coefficient corrected by JARI formula is 0.45 which is very close to those of small foreign cars. To see the effect of the different configurations on the aerodynamic drag, the modifications have been made by changing the hood slope and backlight slope, and putting the add-on-aerodynamic devices on the orignal shape. The rear spoiler was found the most effective one to reduce the aerodynamic drag. It may be concluded that the considerable aerodynamic drag reduction can be achieved by changing the slopes and A-O-A devices at the proper places of the car.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 1995년도 추계 학술대회논문집
• /
• pp.219-224
• /
• 1995

The adaptive wall test section has distinct advantage over the other devices for reduction of wall interference in the wind tunnel testing. For two-dimensional steady flows the wall adaption strategy has been well established and, in some extent, has been effectively applied to three-dimensional steady flows. For unsteady testing, the wall adaptation is conceptually possible but has never been realized in the wind tunnel experiment. In this study, relatively simple adaptive wall models have been proposed and evaluated through numerical tests. The effect of Mach number, frequency, and amplitude of pitching oscillation on the wall interference reduction has been also studied.

• EDISON SW 활용 경진대회 논문집
• /
• 제5회(2016년)
• /
• pp.632-637
• /
• 2016

This study shows what difference would be made to the aerodynamic characteristic with different thickness ratio of the same airfoil, Eppler 387, at low Reynolds number, at the angle of attack of $0^{\circ}$. Konkuk Univ.'s airfoil has a bigger thickness ratio than that of the original Eppler 387 airfoil. The reason for the thicker camber is a Pt 100 ohm heater mounted inside the Konkuk Univ.'s airfoil and this was assumed to make some differences to aerodynamic characteristic. The comparison of these two airfoils' CFD data, provided by EDSION_CFD, with real experiment that had been made in subsonic wind tunnel at Konkuk Univ. is done. A finer result would come out if the complement of the homogeneity of the wind tunnel's fluid is done in the future.

• 대한기계학회논문집B
• /
• 제30권4호
• /
• pp.373-380
• /
• 2006

Annubar is one of popular tools to measure the exhausted gas flow rate from the stacks. For the accurate monitoring of the amount of discharged pollutants, calibration of annubar is very important. Calibration of annubar has been carried out in a wind tunnel. When the length of annubar is longer than the test section size of wind tunnel, it is very difficult to find out typical value of annubar coefficients. So, a measurement technique to calibrate annubar longer than the size of the test section of wind tunnel must be developed. In the present study, an experiment is performed to measure the annubar coefficients in such a limited size of the wind tunnel. The experimental annubar coefficient by using a partial blocking technique is very close to the annubar coefficient of normal condition.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
• /
• 제10권S_1호
• /
• pp.11-22
• /
• 2001

Observations related to the along-wind dispersion of puffs were collected from 12 field sites and from a wind tunnel experiment and used to test simple similarity relations. Because most of the date made use of concentration time series observation from fixed monitors, the basic observation was t, the standard deviation of the concentration time series. This data also allowed the travel time, t, from the source to the receptor to be estimated, from which the puff advective speed ue, could be determined. The along-wind dispersion coefficient, x, was then assumed to equal tue. The data, which extended over four orders of magnitude, supported the similarity relations t=0.1 t and x=1.8 $u^*$t, where t is the travel time and $u^*$ is the friction velocity. About 50% of the observations were within a factor of two of the predictions based on the similarity relations.

• Wind and Structures
• /
• 제20권4호
• /
• pp.527-548
• /
• 2015

Aeroelastic wind tunnel experiments were conducted for conventional and tapered super-tall building models to investigate the effect of taper on fundamental aeroelastic behaviors in various incident flows. Three incident flows were simulated: a turbulent boundary-layer flow representing urban area; a low-turbulent flow; and a grid-generated flow. Results were summarized focusing on the effect of taper and the effect of incident flows. The suppression of responses by introducing taper was profound in the low-turbulence flow and boundary-layer flow, but in the grid-generated flow, the response becomes larger than that of the square model when the wind is applied normal to the surface. The effects of taper and incident flows were clearly shown on the normalized responses, power spectra, stability diagrams and probability functions.

• 한국공간구조학회논문집
• /
• 제13권1호
• /
• pp.51-57
• /
• 2013

There can be diverse causes in the destruction of a large space structure by strong wind such as characteristics of construction materials and changes in internal and external wind pressure of the structure. To evaluate the wind pressure of roof against the large space structure, wind pressure experiment is performed. However, in this wind pressure experiment, peak internal pressure coefficient is set according to the opening of the roof in Korea wind code. In this article, it was tried to identify the change of internal pressure coefficient and the characteristics of wind pressure coefficient acting on the roof by two kinds of opening on the side of the structure with Hyperbolic Paraboloid Spatial Structures roof. When analyzing internal pressure coefficient according to roof shape, it was found that minimum (52%) and maximum (30%~80%) overestimation was made comparing to partial opening type proposed in the current wind load. It is judged that evaluation according to the opening rate of the structure should be made to evaluate the internal pressure coefficient according to load.

• Journal of Advanced Marine Engineering and Technology
• /
• 제40권4호
• /
• pp.330-335
• /
• 2016

본 논문에서는 설계된 100 W급 헬리컬 수직축 풍력발전기의 공기 역학적 출력 및 유동 특성에 관하여 연구하였다. 이를 위하여 100 W급 헬리컬 수직축 풍력발전기 로터를 설계하였고 풍동 시험과 동일한 환경을 적용한 3차원 전산유동해석을 수행하였다. 전산유동해석 결과를 통하여 공기 역학적 출력과 헬리컬 유동 특성을 확인하였다. 마지막으로 실제 크기의 수직축 풍력발전기에 대한 풍동 시험을 수행하여 전산유동해석에서 예측한 공기역학적 출력과 비교 검증하여 전산유동해석 기법의 타당성을 확인하였다.

• 대한공업교육학회지
• /
• 제32권1호
• /
• pp.117-133
• /
• 2007

이 연구는 중등학교 학생들에게 비행의 원리를 이해하고 항공 기술 분야에 흥미를 가질 수 있도록 하기 위해 학교 현장에 적용 가능한 교수-학습 자료인 학습용 풍동의 힘 측정 장치를 개발하였다. 연구의 내용은 학습용 풍동의 힘 측정 장치 개발과 실험으로 이루어져 있다. 이 연구에서 얻은 주요 결과를 정리하면 다음과 같다. 공과대학 기계계열 학과나 항공연구소 등에서 사용하는 고가의 Load cell을 이용한 장치 대신에 지렛대 원리를 활용한 간단한 구조이다. 종합된 하나의 장치로 양력, 항력 및 유체 저항 비교 실험이 가능하다. 에어포일 받음각에 따른 양력 계수는 실험값과 이론값이 전체적으로 비슷한 경향성을 갖으며, 실속 현상은 실험값이 이론값보다 더 큰 받음각에서 나타났다. 에어포일 받음각에 따른 항력 계수는 실험값과 이론값이 전체적으로 비슷한 경향성을 갖으며, 실험값은 이론값에 비해 항력 계수의 증가 비율이 완만하게 증가하였다.

• 생물환경조절학회지
• /
• 제17권2호
• /
• pp.83-89
• /
• 2008

작물은 복잡한 형상 때문에 CFD모델에서 다공성 매체로 설계된다. 작물이 고려된 CFD 모델 해석을 위해서는 작물군락의 공기저항값을 입력하여야 하며, 이 값은 작물에 따라 달라진다. 본 연구에서는 풍동실험을 통해 국화군락의 공기저항 값을 구하였다. 풍상측에서는 풍속과 재식밀도가 증가할수록 정압이 증가하였다. 풍하측에서는 풍속이 증가할수록 정압이 낮아졌으나 재식밀도의 영향은 크게 받지 않는 것으로 나타났다. 풍속과 재식밀도가 증가할수록 풍상측과 풍하측의 압력차가 커지는 것으로 나타났다. 국화군락의 공기저항값인 항력계수 $C_d$값은 0.22였으며, Fluent 프로그램의 공기저항 계수로 이용한다. CFX 프로그램에서 필요로 하는 다공성 매체의 특성값 $K_Q$는 재식간격 $9{\times}9cm$일 때 2.22, $11{\times}11cm$일 때 1.81, $13{\times}13cm$일 때 1.07이었으며, 이 값을 CFX 프로그램의 quadratic resistance coefficient로 입력한다.