An important variable in the oil-water separation process is the size and dispersion diagram of the bubbles formed in the induced gas flotation(IGF). In this study, the influence of the behavior and characteristics of the fine bubbles generated in the IGF device on the oil-water separation performance was evaluated by a numerical analysis method. For this reason, it constitutes Grid system suitable for bubble characteristic analysis. By applying Reynolds-averaged Navier-Stokes equations, a continuous abnormal flow analysis model of water and air was established. For the numerical flow analysis model, we applied the Eulerian-Eulerian approach that can be used for the reaction model in which bubbles are formed at one point of the Euler method applied when the base is liquid. As a result, it was confirmed that the bubbles in the IGF device were evenly dispersed as the flow velocity of bubbles increased and the particle size decreased. Such a phenomenon was caused by changes in Reynolds number and drag related to the flow characteristics, and could be explained by Stokes' law of viscosity.

Eutrophication and algal blooms can lead to increase of taste and odor compounds and health problems by cyanobacterial toxins. To cope with these eco-social issues, Ministry of Environment in Korea has been reinforcing the effluent standards of wastewater treatment facilities. As a result, various advanced phosphorus removal processes have been adopted in each wastewater treatment plant nation-widely. However, a lot of existing advanced wastewater treatment processes have been facing the problems of expensive cost in operation and excessive sludge production caused by high dosage of coagulant. In this study, the sedimentation and dissolved air flotation (SeDAF) process integrated with sedimentation and flotation has been developed for enhanced phosphorus removal in wastewater treatment facilities. Design and operating parameters of the SeDAF process with the capacity of 100 m3/d were determined, and a demonstration plant has been installed and operated at I wastewater treatment facility (located in Gyeonggi-do) for the verification of field applicability. Several empirical evaluations for the SeDAF process were performed at demonstration-plant scale, and the results showed clearly that T-P and turbidity values of treated water were to satisfy the highest effluent standards below 0.2 mg/L and 2.0 NTU stably for all of operation cases.

A computational fluid flow analysis of a car has been accomplished to explain the lift characteristics according to the changes of wiper angle and car speed. The present study established the process to get the lift coefficient distribution on the whole range of a wiper operating angle. From the result of the present research, it could be seen that the lift coefficient of a wiper with the lower wiper angle had relatively smaller magnitude. On the other hand, the lift coefficient with the wiper angle near 45° was relatively larger than that with the other wiper angles. The present study also verified the usefulness of the lift coefficient that the lift distributions of various car speeds could be derived from the result of a lift coefficient distribution for only a car speed.

자기부상열차가 중 저속 및 초고속 주행 시 차량의 주행특성 및 교량의 동적 응답 결과를 제시하고자 한다. 수직 자유도 및 회전 자유도를 포함한 10자유도 자기부상열차에 대한 운동방정식을 유도하고, 모드 중첩법을 이용하여 교량의 운동방정식을 구성하였다. 또한 제어 방법으로 UTM01제어기법을 적용하여 수치해석을 수행하였다. 해석 예제로 노면조도, 가이드웨이의 처짐비, 차량 속도 등이 교량의 처짐과 차량의 부상공극 및 여러 가지 변수에 미치는 영향을 파악하였다. 부상공극은 조도의 조건에 따라 그 차이가 확연히 드러나고 또한 자기부상열차의 속도가 증가함에 따라 부상공극이 증가함을 알 수 있었다. 그리고 자기부상열차가 중, 저속 주행 시에는 교량에 대한 영향이 미비하지만 초고속 주행 시 교량에 대한 동적확대계수가 큰 값을 보여주었다.

The sludge flotation/thickening apparatus equipped a micro-bubble generating pump was used to investigate micro-bubble generating properties on operational parameters. We evaluated micro-bubble generating properties as results to be operated the apparatus by operational parameters which are pump discharge pressure, air/water ratio(A/W ratio), air flow rate, and water flow rate. Micro-bubble generating efficiencies in pumps without recycling flow and with 50% of recycling flow was found to be very efficient on optimum A/W ratio from 1.06 to 3.62% and optimum A/W ratio from 1.05 to 4.06%, respectively. In condition of 3.6% of A/W ratio, we showed that the apparatus could be generated 36,000 ppm of micro-bubble concentration to be optimum treatment efficiency in sludge thickening process.