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.

돈사의 시설 및 환기구조에 따른 돼지 호흡기성 질병 발생 가능성

서일환 ( Seo I. -h. ),이인복 ( Lee I. -b. ),황현섭 ( Hwang H. -s. ),홍세운 ( Hong S. -w. ),( Jessie P. Bitog ),유재인 ( Yoo J. I. ),권경석 ( Kwon K. -s. ),김용희 ( Kim Y. -h. ) 한국농공학회 2008 한국농공학회 학술대회초록집 Vol.2008 No.-

The typical diseases for pigs in Korea are Porcine epidemic diarrhea (PED), Porcine reproductive and respiratory syndrome (PRRS), Post weaning multi-systemic wasting syndrome (PMWS), and Porcine respiratory disease complex (PRDC). The main factor for the occurrence of these diseases specially the respiratory diseases is the environmental condition particularly ventilation inside the pig house. Considering that Korea has 4 distinct season, the environmental condition in the pig house changes every season. The purpose of this study was to find the relationship between the configuration of the structure and ventilation system of pig houses and the occurrence of pig respiratory disease. The effect of internal airflow distribution to internal disease dispersion in pig house was analyzed. Several field experiments were conducted at several pig farms to understand the environmental control in relation to disease occurrence. To overcome the difficulties of conducting field experiments and obtain internal airflow visualization quantitatively and qualitatively, computational fluid dynamic (CFD). The accuracy of the simulations was preliminarily examined and improvements were made in the model based form the seasonally collected farm data.

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.

버블 칼럼 광생물반응기의 내부 유동분석을 위한 전산유체역학 시뮬레이션 모델의 이용

유재인,이인복,황현섭,홍세운,서일환,권경석,김용희,Yoo, J.I.,Lee, I.B.,Hwang, H.S.,Hong, S.W.,Seo, I.H.,Bitog, J.P.,Kwon, K.S.,Kim, Y.H. 한국농공학회 2009 한국농공학회논문집 Vol.51 No.5

Photobioreactor (PBR) 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 the culture volume and productivity while supplying optimum environmental conditions, various PBR structures and process control are needed to be investigated. In this study, computational fluid dynamics (CFD) was economically used to design a bubble-column type PBR taking 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 to realize bubbles were compared by theoretical approaches and comparing in a 2D simulation. As a result, the VOF (volume of fluid) model was found to be the most effective model to realize the bubbles shape as well as the flow inside PBR which may be induced by bubble injection. Considering the accuracy and economical efficiency, 0.005 second time step size was chosen for 2.5 mm mesh size. These results will be used as criteria for scale-up in the PBR simulation.

축산 악취의 확산 모델 개발을 위한 현장 실험

홍세운,이인복,황현섭,서일환,권혁진,유재인,권경석,하태환,김용희,Hong, S.W.,Lee, I.B.,Hwang, H.S.,Seo, I.H.,Kwon, H.J.,Bitog, J.P.,Yoo, J.I.,Kwon, K.S.,Ha, T.H.,Kim, Y.H. 한국농공학회 2008 한국농공학회논문집 Vol.50 No.4

Odor is one of the major nuisances in the environment. In most countries, odor annoyance from livestock production is an increasing problem in community. In order to reduce the odor inconvenience and establish a good relation between livestock industries and the surrounding communities, many studies, such as diffusion simulations and field experiments, on the odor dispersion and its reduction have been investigated. These studies need to accompany the aerodynamic approach, as a main mechanism of diffusion phenomenon, and computational fluid dynamics(CFD) can be effectively 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. In this study, as the first step of this study, various phenomena and factors of odor diffusion from livestock houses were investigated through field experiments in 2007. Later, those data will be also used to verify the CFD accuracy as well as to develop 3-dimensional CFD model.

BES 기법을 이용한 자연환기식 육계사의 난방에너지 분석

홍세운,이인복,홍희기,서일환,황현섭,유재인,권경석,하태환,김기성,Hong, S.W.,Lee, I.B.,Hong, H.K.,Seo, I.H.,Hwang, H.S.,Bitog, J.P.,Yoo, J.I.,Kwon, K.S.,Ha, T.H.,Kim, K.S. 한국농공학회 2008 한국농공학회논문집 Vol.50 No.1

Most of the broiler houses in Korea have experienced problems on controlling the environmental conditions such as suitability, stability and uniformity of rearing condition inside the broiler house. It is very critical which if not properly controlled, would cause serious stress on the chickens. It is therefore urgent to develop optimum designs of naturally ventilated broiler house which is appropriate to the four seasons of Korea. Field experiment for this matter is very difficult to conduct due to the unpredictable and uncontrollable weather condition. In this study, the heating load of a naturally ventilated broiler house was calculated using TRANSYS 15 BES program while internal climate and thermal condition were computed using Fluent 6.2. The computed resulted of the conventional ventilation system (A) and upgraded ventilation system (B) (Seo et al, 2007) were compared with each other for cold season. The results of the Building Energy Simulation(BES) indicated that the system B, the upgraded ventilation system made 8% lower total heating load and 47% lower at only the broiler zone compared to the conventional broiler house. Considering the entire broiler house, the existence of middle ceiling made the heating energy 11% lower required than without middle ceiling. Accordingly, the system B with middle ceiling was found to save heating energy by 20% in average. This study showed that the BES program can be a very powerful to effectively compute the energy loads of agricultural building while the energy load is very close related to ventilation efficiency.

딸기 고설재배시설에서의 이산화탄소 농도 유지를 위한 방풍막 설치 효과

김용희(Y.-H. Kim),이인복(I.-B. Lee),전창후(Changhoo Chun),황현섭(H.-S. Hwang),홍세운(S.-W. Hong),서일환(I.-H. Seo),유재인(J.-I. Yoo),J.P. Bitog,권경석(K.-S. Kwon) (사)한국생물환경조절학회 2009 생물환경조절학회지 Vol.18 No.1

딸기 재배용 온실 내 재배 벤치에서 생산량을 높이기 위하여 벤치 주위에서 이산화탄소를 공급하는 경우 환기 등에 의한 풍속으로 인하여 작물 주변의 적정 가스 농도가 유지되지 못하는 현상이 발생한다. 본 연구에서는 이산화탄소를 보존시키고자 벤치 주변에 방풍막을 설치하는 방안에 대하여 분석하였다. 온실 내 벤치와 방풍막을 2차원 CFD 시뮬레이션으로 모델링하고 온실 내 공기의 풍속과 이산화탄소의 공급을 구현하여 보존되는 이산화탄소의 농도 분포를 살펴보았다. 또한 이를 통하여 설계한 온실의 환경조건에서의 적정한 방풍막 설치 높이를 제안하고자 하였다. 시뮬레이션에서 구현한 온실 내 풍속조건은 0.5, 1.0, 1.5 ㎧ 이고, 방풍막의 높이는 미설치, 0.15, 0.30 m이고, 각 조건에서의 이산화탄소 농도를 측정하였다. 설계상의 편의와 시뮬레이션의 간소화를 위하여 벤치위의 작물은 없는 것으로 가정하였다. 일반적인 온실 내의 풍속 조건은 1.0 ㎧로, 시뮬레이션 결과 이 때 벤치 위에서의 평균 이산화탄소 농도는 방풍막 미설치 시 420 ppm, 방풍막 설치 높이 0.15 m일 때 580 ppm, 0.30 m일 때 653 ppm으로 나타났다. 딸기의 최대 생산량을 위한 적정 생육 이산화탄소 농도가 600~800 ppm 정도인 것을 고려하여, 이와 같은 환경조건에서의 방풍막의 설치 높이는 0.30 m가 적당할 것으로 판단하였으나 이산화탄소 공급조건, 직물의 배치 등의 조건 변화에 따른 상황에서의 연구가 추가적으로 수행되어야 할 것이다. 이처럼 방풍막의 설치가 온실 내에 시비한 이산화탄소를 직물 주변에 머무르게 하는 효과가 상당함을 알 수 있었으며, 설계한 환경조건에서 작물별로 적정한 수준의 이산화탄소량이 공급되고 있는지를 판단하기 위하여 CFD 기술이 이용될 수가 있음을 보였다. The influence of windbreak to minimize the ventilation velocity near the plant canopy of a greenhouse strawberry was thoroughly investigated using computational fluid dynamics (CFD) technology. Windbreaks were constructed surrounding the plant canopy to control ventilation and maintain the concentration of the supplied CO₂ from the soil surface close to the strawberry plants. The influence of no windbreak, 0.15 m and 0.30 m height windbreaks with varied air velocity of 0.5, 1.0 and 1.5 ㎧ were simulated in the study. The concentrations of supplied CO₂ within the plant canopy of were measured. To simplify the model, plants were not included in the final model. Considering 1.0 ㎧ wind velocity which is the normal wind velocity of greenhouses, the concentrations of CO₂ were approximately 420, 580 and 653 ppm (1×10?? ㎏/㎥) for no windbreak, 0.15 and 0.30 m windbreak height, respectively. Considering that the maximum concentration of CO₂ for the strawberry plants was around 600-800 ppm, the 0.30 m windbreak height is highly recommended. This study revealed that the windbreak was very effective in preserving CO₂ gas within the plant canopy. More so, the study also proved that the CFD technique can be used to determine the concentration of CO₂ within the plant canopy for the plants consumption at any designed condition. For an in-depth application of this study, the plants as well as the different conditions for CO₂ utilization, etc. should be considered.

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.

새만금 지역 간척지 및 인근 농경지에서의 비산 및 부유먼지의 지역별, 시기별 모니터링

황현섭,이인복,신명호,이광야,홍세운,서일환,유재인,권경석,김용희,Hwang, H.S.,Lee, I.B.,Shin, M.H.,Lee, G.Y.,Hong, S.W.,Seo, I.H.,Yoo, J.I.,Bitog, J.P.,Kwon, K.W.,Kim, Y.H. 한국농공학회 2009 한국농공학회논문집 Vol.51 No.5

A study on fugitive dusts was conducted at Saemangeum reclaimed land and the neighboring farm located at the west coast of Korea. After the area was completely reclaimed in 2006, halophyte plants and several windbreak systems were installed. The distributions of suspended dust particle was regularly measured through field experiment. The size of dust source area was also analyzed periodically and then it was determined to be in the following order: Buan > Gimje > Gunsan. The suspended dust which were dispersed to the neighboring areas were significantly affected by the size of the soil particles, wind velocity and wind direction. The results of Big Spring Number Eight (BSNE) experiments also showed that the concentration of the fugitive dust generated from the reclaimed land was reduced remarkably by the presence of halophyte plants. Recently, in 2008, the measured dust concentration rate was decreased by an average of 30.6%. The average dust concentration is expected to decrease further as more areas are being covered by halophyte plants.

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.