• 한국조경학회지
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• 제30권6호
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• pp.17-25
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• 2003

The physical components of a river, such as water surface width/river width ratio, water level, and flow velocity vary according to different flowrates. Moreover, the riverside landscapes are greatly affected by the change of physical components of the stream or river. This paper provides an analysis of the influence of changing physical components of a river on the riverside landscape using a survey-based quantification method. The questionnaire was developed based on current literature, and was submitted to 326 people who each visited a representative station along the riverside.This survey was implemented three times at each representative station during periods of different flowrates. The results of this analysis and survey have Produced an understanding of the relationship between the variation of physical components and riverside landscapes. Survey results about the flow comparison are summarized as follows. Viewing riverside landscapes, most respondents are sensitive to the change of the flow velocity and prefer high water levels to low water levels. As a whole, respondents prefer abundant stream flows and moderate flow velocity in which they can perceive the flow of water. The minimum instream flows for riverside landscapes is estimated at each representative station by using a survey-based quantification method, and the estimated results of some representative stations were greater than the mean monthly flow at each station. The result of this analysis shows that establishing minimum instream flows for riverside landscapes is not only a technical problem, but also a legal problem. Therefore, in the to establish the instream flows in a river, the estimated results have to be considered as a relative standard. Regarding the survey results, respondents' satisfaction level didn't show any clear inclination according to the variation of various hydraulic properties. In determining the minimum instream flow using such an inquiry method, the structure of riverside scenery may vary according to the change of seasons or months. Therefore, to determine a consistent general inclination about the flow rate, it is necessary to have more detailed flow rates for each season or month combined with more inquiries.

• 물과 미래
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• 제8권2호
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• pp.53-53
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• 1975

한 유역의 수계망조직은 그 유역의 기상학적 및 지상학적 특성의 복합효과에 의하여 형성되는 것이며 유역의 주요수문량인 유량은 이들 하천형태학적 특성에 의하여 큰 영향을 받게된다. 따라서 본 연구에서는 한강유역의 하천형태학적 특성을 양적으로 분석한 후 이들 형태학적 특성을 유역의 유출특성과 상관시켰다. 유출특성으로 선정한 유량은 이수목적을 위한 분석대상이 되는 일 평균 유량과 수질오염통제의 기준이 되는 7일 10년 유량(7-day 10-year low flow)으로서 다음과 같은 절차에 의하여 하천형태학적 특성인자와 상관시켰다.

• 한국환경과학회지
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• 제11권3호
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• pp.191-199
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• 2002

In this study, water protection reservoir is selected as the target which is located at the estuary of Taehwa river to analyze and examine the effects of hydraulic structure on river environment. This study aims at the definition of factors which cause the change of ecological environment of river due to the effects of the sediment protection reservoir, and the proposal of the direction of environmental friendly river space development through the analysis and examination of stream variation conditions and riverbed variation characteristics among many effects of hydraulic structure on river environment before and after removal of the sediment protection reservoir when design flow is yielded. Firstly, in case of removal the existing sediment protection reservoir, the hydraulic variation characteristics like depth drop due to removal of the sediment protection reservoir are thought of little because it is examined that depths drop with about 0.01m and 0.01~0.56m when low flow is yielded and design flood yielded, respectively. Nextly, as the examination result of the variation characteristics of flow velocity in case of removal the existing sediment protection reservoir, it is thought that the concern about riverbed erosion is not serious according to the analyzed result as the mean velocity of the channel section where the velocity varies in case of removal the sediment protection reservoir is about 0.07~1.36m/s when low flow is yielded, and is about 1.02~2.41m/s when design flood is yielded despite riverbed erosion is concerned as it is examined that flow velocity is getting increase as about 0.01m/s when low flow is yielded and about 0.01~0.44m/s when design flood is yielded. Lastly, from the prediction result of riverbed variation for each flow amount condition before and after removal the sediment protection reservoir, it is known that the variation range of riverbed is nearly constant when flow amount of the channel exceeds a specific limit as it is analyzed that the more flow amount, the more erosion and sediment in the channel section of down stream part of the sediment protection reservoir and the sediment protection reservoir~Samho-gyo, and the variation ranges according to flow amount between flood condition and design flood condition have little difference in the channel section of the upstream of Samho-gyo.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.667-672
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• 2000

The Characteristics of the conical vortices on the roof surface of a low-rise building has been investigated by using a PIV(Particle Image Velocimerty) technique. The scaled model of TTU building with 1:92 scaling ratio was used. The Reynolds number based on the free stream velocity and the length of the model was $1.96{\times}10^5$. When the angle of attack for the building model is $45^{\circ}$, the conical vortices are occurred symmetrically and the center of vortices are changed with respect to the angle of the approaching flow. The rotating direction of the conical vortices found to be counter-rotating. The secondary vortex motions are investigated using the instantaneous flow field data.

• 한국안전학회지
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• 제13권3호
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• pp.51-59
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• 1998

The vortex tube is a simple device for separating a compressed fluid stream into two flows of high and low temperature without any chemical reactions. Recently, vortex tube is widely used to local cooler of industrial equipments and air conditioner for special purpose. The phenomena of energy separation through the vortex tube were investigated to see the effects of cold flow inlet-outlet ratios and partial admission rates on the energy separation experimentally. The experiment was carried out with various cold flow inlet-outlet ratios from 0.28 to 10.56 and partial admission rates from 0.176 to 0.956 by varying input pressure and cold air flow ratio. To find best use in a given cold flow inlet-outlet ratio and partial admission rate, the maximum temperature difference of cold air was presented. The experimental results were indicated that there are an optimum range of cold flow inlet-outlet ratio for each partial admission rate and available partial admission rate.

• 분석과학
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• 제26권1호
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• pp.34-41
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• 2013

SPLITT Fractionation (SF)는 콜로이드 입자 및 거대분자들을 둘 혹은 그 이상의 부분(fraction)으로 분획하는 기술이다. SF에서는 시료를 지속적으로 주입하므로 대용량 분획이 가능하다. 일반적으로, SF에서는 얇은 리본모양의 채널을 이용하는데, 채널의 입구와 출구부분에는 각각 flow stream splitter가 설치되어 있어서 채널의 입구와 출구가 위 아래로 두 개씩 존재한다. SF에는 두 가지 작동방법이 있는데, 하나는 conventional mode 이고 다른 하나는 전액 공급 모드(full feed mode, FFD)이다. FFD 모드에서의 분리도는 conventional mode 에 비해 떨어지지만, FFD 모드에는 몇 가지 독특한 장점이 있다. FFD 모드에서는 용매의 주입이 필요하지 않으므로 채널의 디자인 이나 작동이 더 간단하다. 따라서 입구 쪽에 flow stream splitter를 필요로 하지 않으며, 시료와 용매를 주입하기 위하여 두 개의 펌프가 필요한 conventional 모드와는 달리 한 개의 펌프만으로 작동이 가능하다. 또한 용매의 주입이 없으므로 시료가 희석되지 않는다. 이는 환경시료와 같이 콜로이드의 농도가 낮은 시료를 분획하고자 하는 경우 유리하다. 농도가 낮은 환경시료의 분획을 위해서는 종종 농축이 필요하다. 본 연구에서는 입구에는 물론 출구에도 splitter를 사용하지 않는 새로운 대용량 FFD 모드 SF 장치를 만들었다. Splitter가 없으므로 장치를 대형화 할 수 있어서 시료처리량(throughput, TP)을 크게 증가시킬 수 있었다. 산업용 폴리우레탄(polyurethane, PU) 라텍스 입자들을 이용하여 새로운 SF 장치를 테스트하였으며, 폴리아크릴레이트(polyacrylate, PA) 입자를 대상으로 새로운 SF 장치의 TP를 확인하기 위하여 유속 및 $d_c$에 따르는 TP의 변화를 조사하였다.

• 대한환경공학회지
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• 제37권11호
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• pp.607-618
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• 2015

본 연구에서는 CFD 모사와 PIV 기법을 이용하여 실규모의 사이드 스트림 방식의 막 모듈을 대상으로 유입부의 수리구조를 개선하여 모듈로 유입되는 유입 유량을 수직으로 균등하게 분포시킬 수 있는 방안을 제시하고 이를 실험적으로 검증하고자 하였다. 사이드 스트림 방식의 막 모듈을 대상으로 유입 유량을 수직으로 균등하게 분포시킬 수 있는 방안을 CFD로 설계한 결과, 내부 유입 수리구조에 유공 격벽을 설치함으로써 모듈내로의 유입유량은 표준편차 기준으로 약 40% 정도 감소됨을 확인하였다. 또한 CFD 결과를 검증하고 사이드 스트림 막 모듈의 편중된 오염의 원인을 조사하기 위해 수행된 입자영상유속 측정 결과로부터 유입구 반대편 유공에서 막 모듈 내부로 들어오는 수체의 유속이 상대적으로 커 수체의 모멘텀이 유입구 측벽에 강한 전단력을 발생하지만 유입구 반대 측벽에서는 사류가 형성됨을 확인하였다.

• 한국연소학회지
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• 제3권1호
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• pp.71-78
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• 1998

The flame stabilization and the combustion characteristics of diffusion flame formed in the wake of a cylindrical bluff body with fuel injection are studied. With the turbulence generator, the flame stability limits and ion currents were measured and analyzed. The results from this experimental study are summarized as follows. The region with highest average value of ion currents in the middle of flame is moved to the upstream side by the turbulent components of main stream. The flame mass with partially active reaction is moved fast for uniform flow and turbulence generator G3, but the flame mass with relatively slow reaction is moved slowly for turbulence generator G1. If the turbulence generator with strong turbulent component is installed, the turbulent time scale is increased with movement from main stream side to recirculation zone as well as the flame stability limits is deteriorated. Though the special dominant frequency is not appeared in the eddy which exists in flame, high frequency characteristics are appeared in uniform flow and turbulence generator G3, and low frequency characteristics are appeared in uniform flow, turbulence generator G3 and G1.

• 한국습지학회지
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• 제10권3호
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• pp.57-68
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• 2008

현장관측에 기초한 원주천의 기준갈수량에 추가하여 수질향상과 어류서식환경의 개선을 위한 목표 유지유량을 산정하였다. 목표유지유량의 산정은 자연 생태적 기능, 친수환경, 경관을 고려한 수심과 유속을 기초로 하여 구간 또는 지점별 저수로폭을 감안하였다. 각 지점별 저수로 수면 폭에 따른 유속은 0.2m/s으로 하고 수심을 상류 0.1m에서 하류 0.3m까지로 하여 산정한 추가적 유지유량 확보량은 상류지점의 $0.03m^3/s$에서 하류지점의 $0.90m^3/s$이다. 목표한 유지유량의 확보를 위한 방안으로 하수도시스템의 개선에 의한 계곡수와 우수의 방류, 유역관리에 의한 기저유출 증가, 상류수원의 개발과 천변저류지 등을 검토하였다. 검토결과는 목표유량과 부합되는 $0.19m^3/s$에서 $3.42m^3/s$로 기준갈수량의 1.4배에서 2.5배 까지 늘릴 수 있는 가능성을 분석하였다. QUAL2E 모형의 적용을 통하여 유지유량 증가에 따른 BOD 수질개선효과를 확인하였다. 원주천 중류의 복원목표종을 갈겨니로 선정하고, 유지유량 증가에 따른 PHABSIM 모형에 의한 서식적합도는 현저히 향상되어 유량증대가 수질과 어류서식환경을 개선하는 것으로 나타났다.

• 한국물환경학회지
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• 제22권5호
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• pp.943-951
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• 2006

Spatial distribution of water pollution in the Gap Stream was investigated from October to November, 2005. Sampling was conducted three times including effluents discharged from a wastewater treatment plant (WWTP) and a dam reservoir during the low-flow period. As a typical urban stream, total nitrogen and inorganic nitrogen concentrations increased toward downstream. Ammonia concentration was the highest in the treated water of the wastewater treatment plant and the lowest nitrate concentration was found in the effluent of the dam reservoir. A part of soluble reactive phosphorous (SRP) in total phosphorous was 22~54% in the upstream reach of WWTP in the Gap Stream whereas 68~73% in the downstream reach. Mean chlorophyll-a concentration ranged from 1.6 to $11.0{\mu}g/L$ and it tends to increase toward downstream except for WWTP effluent. As expected, untreated wastewater and WWTP effluent were suggested as the major sources of water pollution in the Gap Stream. In this study, the water pollution of the Gap Stream is a significant undergoing typical eutrophication, caused by excessive phosphorus and nitrogen nutrients from WWTP located in the watershed. As a result, the critical factor for the water pollution was evaluated to dissolved inorganic nitrogen and phosphorus nutrients. Particularly, SRP is a most important for the eutrophication. It suggest that may occur in the most urban streams of Korean peninsula. Therefore, because the necessity of water pollution management in the urban stream, inorganic N and P nutrients should be included as an essential component of water quality criteria in the advanced water quality project of Korean Government by enforcing of water quality assessment and total maximum daily loads (TMDLs).