• 한국소음진동공학회논문집
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• 제24권3호
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• pp.180-188
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• 2014

현대자동차그룹은 HSM이라고 불리는 간략화된 차량 모델에 대하여 썬루프 버페팅 현상의 실험적인 조사를 시행하였다. 현대자동차그룹은 어떤 CFD솔버가 충분한 정확도를 가지고 썬루프 버페팅 현상을 예측하는지 조사하기 위해 상용CFD공급업체의 참여를 요청하였다. ANSYS Korea는 이번 조사에 참여하여 ANSYS fluent를 이용하여 HSM의 썬루프 버페팅에 대한 수치해석을 수행하였다. 먼저 유동장 검증을 위해 풍속 60 km/h에 대하여 썬루프가 닫힌 HSM모델에 대하여 해석을 수행하였다. HSM상부 면의 세 지점에서 속도 분포를 예측하였고, 이는 시험결과와 비교되었다. 그런 다음 고해상도 난류 모델인 DES를 이용한 해석이 전 풍속영역에 걸쳐 수행되었다. 버페팅 주파수와 버페팅 음압레벨이 예측되었고, 이는 시험결과와 비교되었다. 이를 통해 실제 차량 개발을 위한 CFD의 예측 가능성에 대하여 결론을 얻을 수 있었다.

• 한국해양학회지
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• 제21권4호
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• pp.203-210
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• 1986

선형, 평행 수송모델을 세우고 이상적인 항해에 적용하였다. 이 간단한 해석 모델로서 지금 까지 예지되어 온 황해 남부의 역풍류 현상을 적절히 설명할 수 있 다. 수심이 임계수심(본모델 바다에서는 Hc=53m임)보다 깊은 해역에서는 압력 경도 력이 바람응력보다 우세하여 역풍류를 야기시킨다. 추정된 역풍류 속도는 풍속과 함께 증가하며 최대 역풍류는 황해의 깊은 골을 따라나타난다. 하계의 전형적인 남 풍속도 5-10노트에 대해서 황해골을 따른 역풍류(남향류)속도는 1-5cm s$^{-1}$로 추정된다. 반면에 동계의 전형적인 북풍속도 10-15노트에 대해서는 역풍류(북향류) 속도는 5-12cm s$^{-1}$ 이다. 이와 같은 속도 범위는 각각 하계의 황해 저층냉수 와 동계의 황해난류의 잠입속도에 대한 개략적인 추정치로서 사용될 수 있다.

• 대한기계학회논문집B
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• 제27권4호
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• pp.466-475
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• 2003

The gun-type gas burner adopted in this study is generally composed of eight slits and swirl vanes. Thus, this paper is studied to investigate the effect of slits and swirl vanes on the turbulent flow fields in the horizontal plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rate 450 $\ell$/min in the test section of subsonic wind tunnel. The axial mean velocity component in the case of burner model with only swirl vanes shows the characteristic that spreads more remarkably toward the radial direction than axial one, it does, however, directly opposite tendency in the case of burner model with only slits. Consequently. both slits and swirl vanes composing of gun-type gas burner play an important role in decrease of the speed near slits and increase of the flow speed in the central part of a burner because the biggest speed spurted from slits encircles rotational flow by swirl vanes and it drives main flow toward the axial direction. Moreover, the turbulent intensities and turbulent kinetic energy of gun-type gas burner are distributed with a fairly bigger size within X/R<0.6410 than burner models which have only slits or swirl vanes because the rotational flow by swirl vanes and the fast jet flow by slits increase flow mixing, diffusion, and mean velocity gradient effectively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.341-346
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• 2001

The gun-type gas burner adopted in this study is generally composed of some slits and swirl vanes. Therefore, this paper is studied to investigate the effect of slits and swirl vanes on the turbulent flow fields in the horizontal plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rate $450\;{\ell}/min$, which is equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of subsonic wind tunnel. When the burner has only swirl vanes, the axial mean velocity component shows the characteristic that spreads more remarkably toward radial direction than axial one, but when it has only slits, that is developed spreading more toward axial direction than radial one. Therefore, because the biggest speed is spurted in slits and it derive main flow toward axial direction encircling rotational flow that comes out from swirl vane that is situated on the inside of slits, both slits and swirl vanes composing of cone type gas burner act role that decreases the speed near slits and increases the flow speed in the central part of a burner. Moreover, because rotational flow by swirl vanes and fast jet flow by slits increase turbulent intensities effectively coexisting, the turbulent kinetic energy is distributed with a bigger size fairly near slits than burner models which have only slit or swirl vanes within X/R<0.6410.

• 동력기계공학회지
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• 제5권2호
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• pp.22-29
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• 2001

This paper represents axial mean velocity, turbulent kinetic energy and swirl number based on momentum flux measured in the X-Y plane and Y-Z plane respectively of a cone type gas swirl burner by using X-probe from the hot-wire anemometer system. This experiment is carried out at flow rates 350 and $450{\ell}/min$ respectively, which are equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of a subsonic wind tunnel. Axial mean velocities and turbulent kinetic energies show that their maximum values exist centering around narrow slits situated radially on the edge of and in the forefront of a burner until $X/R{\fallingdotseq}1.5$, but they have a peculiar shape like a starfish diffusing and developing into inward and outward of a burner by means of the mixing between flows ejected from narrow slits, an inclination baffle plate and swirl vanes respectively according to downstream regions. Moreover, they show a relatively large value in the inner region of 0.5$S_m$ obtained by integration of velocity profiles shows a characteristic that has an inflection point composing of the maximum and minimum value until X/R<3, but shows close agreement with the geometric swirl number after a distance of X/R=3.

• 한국정보통신학회논문지
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• 제19권8호
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• pp.1773-1779
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• 2015

본 논문은 컬러 클러스터 MIMO 기술을 적용하여 육상과 해상 간의 저비용 고속 무선 데이터 전송이 가능한 해상 가시광 통신 시스템을 제안한다. 제안하는 시스템은 각 컬러 클러스터에 50개의 RGB LED 로 구성되며, 온-오프키잉을 사용하여 변조한다. 수신기에서는 선택적 합성기술을 수행하여 컬러 클러스터의 다이버시티 효과를 얻어 비트오율 개선을 제공한다. 성능 실험에서는 해상 채널 구성을 위해 대기 난류 조건에서 바다 상태 데이터 (파고, 풍속 등)를 Pierson-Moskowitz 및 JONSWAP 스펙트럼에 적용하여 구현하였으며 해상 링크 품질을 통신거리와 비트 오율을 통해 분석하였다. 시뮬레이션 결과를 통하여 제안한 시스템은 국제항로표지협회의 해상 부표식에 충족하고, 고출력 LED를 사용하기 때문에 충분한 조명을 동시에 제공할 수 있는 효율적인 해상 가시광통신 기술임을 보여주고 있다.

• 대한기계학회논문집B
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• 제27권9호
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• pp.1299-1308
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• 2003

This paper is studied to investigate the effect of slits and swirl vanes on the development of turbulent flow fields in gun-type gas burner with a cone type baffle plate because this gas burner is generally composed of eight slits and swirl vanes. All of turbulent characteristics including mean velocities were measured in the horizontal plane and cross section by using X-type hot-wire probe from hot-wire anemometer system. This experiment is carried out at flow rate 450 l/min in the test section of subsonic wind tunnel. Slits cause the fast jets, and then they have the characteristic that the flow is not adequately spread to radial direction and has long flow length and very small flow velocity distribution in the central part. On the contrary, swirl vanes does not have long enough for adequate flow length to downstream because the rotational flow diffuses remarkably to radial direction. However, the suitable arrangement between slits and swirl vanes causes effective flow width and flow length, and then it promotes fast flow mixing over the entire region including central part to increase turbulence more largely and effectively. Therefore, it is thought as a very desirable design method in gun-type gas burner to locate slits on the outside of swirl vanes.

• 대한기계학회논문집B
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• 제25권2호
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• pp.225-234
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• 2001

This paper represents the vector fields, three dimensional mean velocities, the turbulent intensities, the turbulent kinetic energy, and the Reynolds shear stresses in the X-Y plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rates 350 and 450ℓ/min respectively, which are equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of subsonic wind tunnel. The vector plot shows that the maximum axial mean velocity component exists in the narrow slits situated radially on the edge of gas swirl burner, for that reason, there is some entrainment phenomena of ambient air in the outer region of burner. Moreover, mean velocities in the initial region are largely distributed near the outer region of burner at Y/R≒0.97, but they diffuse and develop into the center flow region of burner according to the increase of axial distance. The turbulent intensities and the turbulent kinetic energy due to large inclination of mean velocity and swirl effect show that the maximum value in the initial region of burner is formed in the narrow slits situated radially on the edge of gas swirl burner and large values are mainly formed in the entire region of burner after X/R=2.4358, hence, the combustion reaction is anticipated to occur actively near this region. And the Reynolds shear stresses are also largely distributed from slite to vanes of gas swirl burner in the intial region, but their values largely disappear after X/R=3.2052.

• 대기
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• 제33권4호
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• pp.343-354
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• 2023

Turbulence produced on roadways is one of the major factors determining the dilution rates at the initial stage of traffic emissions of air pollutants and, thus, the distribution of air pollutants near the roadways. Field experiments were conducted on Gyeongbu Highway, one of the busiest highways in Korea, for 4~7 days in winter, spring, and summer. Two three-dimensional ultrasonic anemometers were installed on both sides of the highway to estimate turbulence intensities (vertical wind fluctuation and kinetic turbulence energy) induced by the roadway. Roadway-induced turbulence consists of three components: structural road-induced turbulence (S-RIT), thermal road-induced turbulence (T-RIT), and vehicle-induced turbulence (VIT). The contribution of T-RIT to the total RIT was insignificant (less than 10%), and the majority of RIT was S-RIT (by the highway embankment) and VIT. In this study, we propose the empirical relationships of VIT as a function of traffic density and wind speed under free-flow traffic conditions. Although this empirical relationship appears to underestimate the VIT, it can be applied to the air quality models easily because the relationship is simple and only needs readily obtainable input variables (wind speed and traffic information).

• 한국농림기상학회지
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• 제15권1호
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• pp.17-25
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• 2013

본 연구는 복잡한 산악지형에서 바람장 변화를 해석하고, 산불발생시 확산방향을 예측하여 산불방지 전략에 활용하기 위해서 수행되었다. 연구 대상지는 2000년 4월 7일 산불이 발생하여 10일간 진행되었던 삼척지역을 대상으로 하였다. 삼척 산불피해지는 복잡한 산악구조를 가지고 있는데 먼저 중규모 기상 모델인 WRF를 사용하여 대상지에 설치한 AWS(4 지점)의 관측결과와 비교하였다. WRF 모의 결과, 4개 지점의 풍속은 AWS 관측지점의 풍속에 비해 5~8m/s(200% 과대평가) 강하였으며, 관측된 풍향은 지점마다 다양하게 나타난 것에 비해 모의된 풍향은 모든 지점에서 서풍계열로 나타났다. 결과적으로 WRF와 같은 중규모 기상모델은 복잡한 산악지형에서의 바람장 변화를 잘 모의하지 못하였다. 이러한 문제점을 해결하기 위해 미기상 대기유동장 수치모형인 ENVI-met 프로그램을 이용하여 지표면 높이에서 삼척 LTER 지역의 국지규모 바람장을 모의하였다. 지형효과에 의한 모델의 민감도를 위해 다양한 초기 조건(기류, 온 습도, 대기난류, 토양 및 식생 모형)들을 고려하여 분석하였다. ENVI-met 모의결과, 풍속은 실측과 비교할 때 약 70%의 정확도를 보였으며, 풍향은 계곡부와 능선부에서 지형효과로 인한 변화를 잘 반영하였다. 향후 ENVI-met은 산불확산예측 및 산불방지전략 수립을 위해 미기상 대기유동장 수치모형을 이용하여 산악지역의 미기상 해석에 관한 연구가 필요할 것으로 판단된다.