SIMULATION OF AN ARRAY OF FENCES IN SAEMANGEUM RECLAIMED LAND USING CFD TECHNOLOGY

( J. P. Bitog ),이인복 ( I. -b. Lee ),홍세운 ( S. -w. Hong ),황현섭 ( H. -s. Hwang ),서일환 ( I. -h. Seo ),유재인 ( J. -i. Yoo ),권경석 ( K. -s. Kwon ),최지선 ( J. -s. Choi ) 한국농공학회 2009 한국농공학회 학술대회초록집 Vol.2009 No.-

This paper discusses about the quantitative effect of windbreak fences on wind velocity in the reclaimed land at Saemangeum semi-arid desert in South Korea. Windbreak fences were constructed in the reclaimed land purposely to prevent the generation and diffusion of dust. Using CFD simulations, the effects of fence porosity, fence height, and the distance between the adjacent fences were investigated. A wind tunnel experiment was initially conducted and data gathered were used to develop the CFD models. From the experiments and CFD simulations, the overall percentage difference of the measured velocities was 7.81% which is generally acceptable to establishing the reliability of the CFD models. The reduction effect on wind velocity was measured in between the adjacent fences up to a height of 0.6 m from the ground surface. In terms of porosity (ε= 0, 0.2, 0.4, 0.6), 0.2 was found to be the optimum value. Conversely, the effect of fence height (0.6, 0.8 and 1.0 m) showed no significant difference; therefore, 0.6 m height is recommended. In addition, the effect of distance between the adjacent fences (2, 4 and 6 m) having a 0.2 porosity has decreased to about 75% regardless of the distance. In the case of the reclaimed land in Saemangeum, a decrease of 75% can prevent the generation and diffusion of dusts. However, the source of dusts is very large. Therefore, constructing an array of windbreak with 6 m distance between them is deemed necessary.

전산유체역학을 이용한 돈사 건물 간 입자 전파 분석

최지선 ( J. -s. Choi ),이인복 ( I. -b Lee ),서일환 ( I. -h. Seo ),김용희 ( Y-h Kim ) 한국농공학회 2010 한국농공학회 학술대회초록집 Vol.2010 No.-

한국의 양돈산업은 생산성 증대를 위해 대규모화 추세를 보이고 있다. 대형화로 인하여 질병 발생 시 확산 위험이 높아지고 피해규모 역시 커지며 특히 사료나 가축분뇨 등에서 발생하는 먼지에 병원체가 부착되어 전파될 수 있기 때문에 위생조건 관리와 유지의 중요성이 강조된다. 공기 오염물질의 확산은 공기의 유동장에 따라 그 양상이 달라지는데 우리나라는 약 64% 가 산악지대이기 때문에 지형 조건이 공기의 유동장 형성에 중요한 요소로 작용한다. 본 연구에서는 돈사 건물 간 공기 오염물질에 대한 전파에 대하여 공기역학적 분석을 실시하고자 한다. 이를 위하여 현장실험을 통해 돈사 건물 주위와 그 지역의 기상조건을 파악하고, 양돈장 주위의 분진을 포집하여 바이러스의 발생 여부와 입자의 이동을 확인함으로써 질병의 전파 경로의 예측하고자 한다. 현장실험에서 점 측정 및 불안정하고 예측이 어려운 환경 조건 등의 한계를 보완하고자 전산유체역학(CFD) 기술을 이용하여 이를 구현하였다. GIS수치지도에서 필요한 정보를 추출하고 CAD프로그램 등을 이용하여 지형을 3차원으로 구성한다. 구성된 3차원 지형은 Gambit을 이용하여 격자를 생성 한 뒤Fluent를 이용하여 공기의 유동을 구현할 수 있다. 본 연구에서는 국내 양돈장 구조 및 지형 등에 따른 입자확산 모델 연구를 통하여 각 건물 간 영향을 미치는 영향이나 위험도를 산정하여 농장 설계 시 이를 고려할 수 있는 방안을 모색할 수 있도록 한다.

CFD를 활용한 복잡한 지형 내 축산 악취의 확산 예측

홍세운 ( S. -w. Hong ),이인복 ( I. -b. Lee ),황현섭 ( H. -s. Hwang ),서일환 ( I. -h. Seo ),유재인 ( J. -i. Yoo ),( J. P. Bitog ),권경석 ( K. -s. Kwon ),최지선 ( J. -s. Choi ) 한국농공학회 2009 한국농공학회 학술대회초록집 Vol.2009 No.-

Odor is one of the major nuisances in the environment. In most countries, odor annoyance from livestock production is an increasing problem in the community. In order to reduce the odor inconvenience and establish a good relation between livestock industries and the surrounding communities, many studies on the odor dispersion, such as diffusion simulations and field experiments have been investigated. Computational fluid dynamics (CFD) has been effectively and widely used to study this kind of research. CFD considers both various wind conditions as well as topographical conditions to study aerodynamic phenomenon. Therefore, the ultimate objective of the study was to develop an aerodynamic model to predict qualitatively and quantitatively odor diffusion from livestock. During the first year of this 3-year study, various phenomena and factors of odor diffusion from livestock houses were investigated from field experiments. In the second year, mesh models of the study area with a 1.8km radius were built with 5m resolution. Modules for the atmospheric phenomena were also made by user defined functions and linked into a main computing module. The dispersion of odor was predicted by the 3D CFD model and practically agreed to the field measured data. Later, this model will be used to arrange the odor-related conflicts as well as to predict the odor dispersion according to various meteorological conditions.

CFD 시뮬레이션을 활용한 미세조류 배양용 버블 칼럼 광생물반응기 설계

유재인 ( J. -i. Yoo ),이인복 ( I. -b. Lee ),황현섭 ( H. -s. Hwang ),서일환 ( I. -h. Seo ),홍세운 ( S. -w. Hong ),( J. Bitog ),권경석 ( K. -s. Kwon ),최지선 ( J. -s. Choi ) 한국농공학회 2009 한국농공학회 학술대회초록집 Vol.2009 No.-

Photobioreactors (PBRs) that houses and cultivates microalgae providing a suitable environment for its growth, such as light, nutrients, CO2,heat, etc. is now getting more popular in the last decade. Among the many types of PBRs, the bubble column type is very attractive because of its simple construction and easy operation. However, despite the availability of these PBRs, only a few of them can be practically used for mass production. Many limitations still holdback their use especially during their scale-up. To enlarge their culture volume and productivity by supplying optimum environmental conditions, various PBR structures and processes for controlling are needed to be compared. In this study, computational fluid dynamics (CFD) was used to design a bubble-column type PBR to economically take the place of field experiments. CFD is a promising technique which can simulate the growth and production of microalgae in the PBR. To study bubble column PBR with CFD, the most important factor is the possibility of realizing bubble. In this study, multi-phase models which are generally used were compared by theoretical approaches and 2D preliminary simulations. As a result, the VOF (Volume of Fluid)model was found to be the most effective to realize the bubble shape and flow inside PBR which is made by bubble injection. Considering the accuracy and economical efficiency, 0.005 sec of time step size was chosen for 2.5 mm mesh size. With these initial conditions, 3-D PBR trial simulation and PIV (Particle Image Velocimetry) validation test were conducted. The verified CFD simulation model will be used as criteria for PBR scale-up research.

새만금 간척 지역의 비산 및 부유 먼지 확산 모니터링 및 예측

황현섭 ( H. -s. Hwang ),이인복 ( I. -b. Lee ),서일환 ( I. -h. Seo ),홍세운 ( S. -w. Hong ),( J. Bitog ),유재인 ( J. -i. Yoo ),권경석 ( K. -s. Kwon ),최지선 ( J. -s. Choi ) 한국농공학회 2009 한국농공학회 학술대회초록집 Vol.2009 No.-

A study on fugitive dust dispersion was conducted in a 40,100ha reclaimed land located at the west coastal part of Korea. The dusts are composed mainly of minerals with high salinity that is very harmful to human’s health such as skin and eye irritations and If frequently inhaled, respiratory disease can occur. More so, the highly concentrated salty dusts can be very harmful to farms located nearby. A computational fluid dynamics (CFD) model was developed to predict the dispersion of fugitive dust from Saemangeum reclaimed land considering the topography of the area. Field experiment is the ideal method to understand real aerodynamic phenomenon. Nevertheless, it is very difficult to find a correlation between weather condition and dust dispersion because of limited measuring points, labor and time. Moreover, the weather condition is always unstable and unpredictable as well as cannot be artificially controlled. To overcome these limitations, CFD simulation was used to quantitatively and qualitatively analyze the dust dispersion phenomenon according to various weather conditions. Great effort has been needed to improve the CFD accuracy with topographical design, mesh structure, particle generation, and computational process by parallel processing technique. Results from this study in 2006, 2007 and 2008 showed that the changes in dust source are highly connected with the changes of dust concentration. The dust concentration shows a decreasing trend in 2008, and it is expected to decrease further as more dust source areas are being covered by plants. The samples analyzed through SEM showed that most dust particles are large in size with irregular dimension. Dust dispersion ranges of CFD result were compared with that of field experiment at the same measuring points for the CFD validity, and the results at stable weather condition were very acceptable with an average error of 6.8%. The vertically dust concentration of the CFD results also became very similar with the general log-profile of fugitive and suspended dust presented by Gillies et al. (2004). The results also showed that the dispersion of the fugitive dust was mainly affected by particle size, wind speed as well as wind direction. On the basis of 10 μm particle size, the diffused distance of fugitive dust resulted in 3,100m with the wind speed of 1.7m/s at 10 m height from the ground while 6,300m with 3.9m/s. Through this study, it was found that the CFD technology can be effectively used to complement the field experiment at studies and more accurate of reliable results can be obtained.