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.

A wind tunnel study on aerodynamic porosity and windbreak drag

J. P. Bitog,이인복,H.-S. Hwang,M.-H. Shin,홍세운,I.-H. Seo,E. Mostafa,Z. Pang 한국산림과학회 2011 Forest Science And Technology Vol.7 No.1

Natural windbreaks such as trees are very efficient barriers to high velocity winds. The windbreaks exert drag force causing a net loss of momentum and thus disturb the characteristics of flow. The main factors which can affect the efficiency of the windbreaks are tree height, width, tree arrangement, porosity, etc. However, tree porosity which is strongly related to the windbreak drag is very difficult to establish. In this study, the results of a wind tunnel test were introduced to find the aerodynamic porosity and resistance factor of a tree windbreak. Black pine tree (Pinus thunbergii), a typical tree windbreak in Korea was chosen as the experimental tree. With the main factors of wind velocity, static pressure and density of the tree, the aerodynamic porosity as well as the resistance factor of the tree was found. The average porosity at varied tree density were found to be 0.91, 0.69 and 0.42 for one, two and three trees, respectively. The resistance factors which can be equaled to the drag coefficient were 0.55, 0.82 and 1.08 for one, two and three trees, respectively. The determined aerodynamic porosity and windbreak drag will be used later as input data in computer simulation studies such as computational fluid dynamics (CFD). Moreover, the experimental procedure as well as the use of real trees in the wind tunnel experiment of finding the aerodynamic porosity and windbreak drag of various tree windbreaks was established through this study.

Optimised hydrodynamic parameters for the design of photobioreactors using computational fluid dynamics and experimental validation

Bitog, J.P.P.,Lee, I.B.,Oh, H.M.,Hong, S.W.,Seo, I.H.,Kwon, K.S. Academic Press 2014 BIOSYSTEMS ENGINEERING Vol.122 No.-

A numerical simulation using computational fluid dynamics (CFD) was utilised to investigate the flow hydrodynamics of cylindrical bubble column type photobioreactors (PBRs) with a 30l culture medium. To establish the reliability of the simulation study, the CFD model was validated using particle image velocimetry (PIV) computed data under various air flow rates. There were 32 simulation cases for the study comprising two PBR designs, four air flow rates and four nozzle size diameters. Hydrodynamic analyses such as % volume of dead zones, average circulation time and turbulence intensity inside the simulated PBRs were evaluated. Results have shown that the most appropriate PBR for microalgae cultivation was a design with internal baffle and an extended cone-shaped bottom section. In addition, the recommended nozzle diameter was found to be 10 mm and a minimum air flow rate of 0.10 vvm. To eliminate dead zones inside the PBR, the flow rate can be slightly increased but should not exceed 0.15 vvm. Practical evaluation through laboratory experiments has further confirmed the results of the study where the biomass concentration of Chlorella vulgaris from the proposed PBR was significantly higher compared to the standard PBR design. Based on the numerical investigation and practical evaluation, the improved PBR can be seen to be more effective in culturing microalgae particularly for larger scale mass production.

나무의 공극률과 방풍 효과에 대한 풍동 실험

제시비톡 ( J. P. Bitog ),이인복 ( I. -b. Lee ),황현섭 ( H. -s. Hwang ),홍세운 ( S. -w. Hong ) 한국농공학회 2010 한국농공학회 학술대회초록집 Vol.2010 No.-

Natural windbreaks such as trees are very efficient barriers to high velocity winds. The windbreaks exert drag force causing a net loss of momentum and thus disturb the characteristics of flow. The main factors which can affect the efficiency of the windbreaks are tree height, width, tree arrangement, porosity, etc. However, tree porosity which is strongly related to the windbreak drag is very difficult to establish. Recently, computational fluid dynamics (CFD) have been actively used to investigate wind flow characteristics around artificial and natural windbreaks such as trees. As a first step in the simulation, the CFD model had to be designed as a porous media because of the complexity of the physical structure. In this study, the results of wind tunnel test were introduced to find the porosity and aerodynamic resistance of a tree windbreak. Black pine tree (Pinus thunbergii), a typical tree windbreak in Korea was chosen as the experimental tree. With the main factors of wind velocity, static pressure, and density of the tree, the aerodynamic porosity as well as the resistance factor of the tree was found. The average porosity at varied tree density were found to be 0.91, 0. 69 and 0.42 for one, two and three trees, respectively. The resistance factors which can be equaled to the drag coefficient were 0.55, 0.82 and 1.08 for one, two and three trees, respectively. The determined aerodynamic porosity and windbreak drag will be used later as input data of CFD models. Moreover, the experimental procedure as well as the use of real tree in the wind tunnel experiment of finding the aerodynamic porosity and windbreak drag of various tree windbreaks was established through this study.

The past, present and future of CFD for agro-environmental applications

Lee, I.B.,Bitog, J.P.P.,Hong, S.W.,Seo, I.H.,Kwon, K.S.,Bartzanas, T.,Kacira, M. Elsevier 2013 Computers and electronics in agriculture Vol.93 No.-

Computational fluid dynamics (CFD) is a proven simulation tool which caters to almost any field of study. The CFD technique is utilized to simulate, analyze, and optimize various engineering designs. In this review, the discussion is focused on the application of CFD in the external atmospheric processes as well as modeling in land and water management. With respect to its application in environmental investigations, numerous CFD studies have been done in the atmospheric processes where generally only the fluid flow characteristics are investigated. The application of CFD to soil and water management is still limited. However, with the present demand for conservation and sustainable management of our soil and water resources, CFD application in this field is fast emerging especially in structure designs of dams and reservoirs where CFD offers fast reliable results with less labor and cost. Every CFD model should be validated in order to be considered accurate and reliable. However, a benchmark or standard procedures in validating CFD models is not yet available. This probably answers why the success of the CFD models is still mostly attributed to the user's skills and experience. At present, the degree of application of CFD to the agro-environmental field is limited by the computing power and software used, however, the fast ever computing power of PCs continually expands the potential of CFD and can be generally more flexible at accounting for the unique aspects of every CFD project. This allows easy access to conduct simulation studies from simple to complex models. In this paper, after a state of art analysis of the past and present application of CFD in the agro-environmental applications, its future directions were discussed, in order to potentially serve as a guide for researchers and engineers on what project or investigations can be conducted.

소형 풍력 발전을 위한 축산 배기팬의 후류 평가

홍세운 ( Sewoon Hong ),이인복 ( Inbok Lee ),( J. P. Bitog ),송상현 ( Sanghyeon Song ),이성복 ( Sungbok Lee ),김용희 ( Yonghee Kim ) 한국농공학회 2010 한국농공학회 학술대회초록집 Vol.2010 No.-

풍력 발전은 풍속의 세제곱에 비례하여 에너지를 생산할 수 있으므로 풍속이 높고 일정할수록 높은 발전효율을 보인다. 풍속이 낮고 변동이 큰 자연풍과 달리 팬에 의하여 인위적으로 생성된 기류는 이러한 관점에서 최적의 적용 대상이라 할 수 있다. 농업 분야에서 축산 시설에서 사용되는 배기팬은 축사 내부의 유해 가스 배출 등의 목적으로 최소환기 이상의 환기량으로 연중 가동되고 있으므로, 본 연구에서는 이에 의해 형성되는 배기팬 후류의 양질의 바람을 발전에 사용하고자 발전 가능성 및 발전 시 배기팬에 나타날 수 있는 부하의 가능성을 사전에 평가해 보고자 하였다. 축산 농가에서 주로 사용되고 있는 50인치 배기팬을 사용하여 실험을 한 결과, 배기팬으로부터 약 3 m정도 거리에서 약 5~7 m/s의 풍속이 유지되었으며, 5 m 이후부터는 풍속이 약 4 m/s 이하로 급격히 감소되는 것으로 나타났다. 배기팬 뒤에 장애물을 설치하여 장애물에 의한 부하를 측정한 결과, 배기팬의 1 m 뒤에 장애물 판을 설치한 경우에는 약 20% 정도의 배기유량이 감소되는 결과를 보였으나, 거리가 증가함에 따라 그 부하는 점차 감소하였다. 배기팬의 소비전력 또한 약 1 m 거리일 때에는 10 % 정도 증가하였지만, 그 이후의 거리들에서는 약 5 % 미만으로 점차 부하는 감소하는 결과를 보였다. 약 3 m 정도의 거리에서는 배기유량과 소비전력에서 장애물이 없을 때와 비교하여 약 5 % 내외의 차이를 보이고 있으며, 실험에 사용된 장애물 판에 비하여 실제 풍력 터빈은 솔리디티가 훨씬 작으므로 부하에 의한 역효과는 더욱 감소할 것으로 예상된다. 이러한 풍력 발전의 가능성에 따라 적정 풍력 터빈의 형상과 위치 등을 결정하고자 전산유체역학 시뮬레이션 툴을 사용하여 배기팬에서 형성되는 복잡한 후류를 모의하고자 하였다. 해석 결과의 검증과 보정을 위하여 실험을 통하여 배기팬 후류의 수평적 풍속 분포를 측정하였고, 배기팬 후면에 다수의 짧은 실을 프로브로 설치하여 유동을 가시화하였다. 실험을 통하여 측정된 수직, 수평적 풍속 분포들은 시뮬레이션에 의한 기류 분포와 비교하여 배기팬에서 생성되는 기류의 프로파일을 생성하는데 활용되었다.

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.

제3발표장 : 생물생산시설 및 환경공학 분야 ; CFD를 이용한 광생물반응기 구조에 따른 바이오매스 생산성 예측

서일환 ( Il Hwan Seo ),이인복 ( In Bok Lee ),JPBitog ( J P Bitog ),권경석 ( Kyung Seok Kwon ),박하아린 ( Ha A Rin Park ) 한국농업기계학회 2013 한국농업기계학회 학술발표논문집 Vol.18 No.1

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.

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.