지하도로는 폐쇄적인 공간 구조와 내·외부 조도 차이로 인해 지상도로와 다른 교통 환경을 형성하며 이러한 특성은 교 통사고에 영향을 미칠 수 있다. 특히 고속도로 터널에서 사고 발생 시 대형 인명 피해로 이어질 가능성이 크다는 점을 고려할 때 지하도로에서도 유사한 우려가 제기된다. 따라서 지하도로의 교통류 특성을 면밀히 분석하여 안전성을 평가하 고 사고 예방을 위한 효과적인 대책을 마련하는 것이 중요하다. 본 연구에서는 서부간선 지하도로 성산 방면의 14개 VDS 검지기 데이터를 기반으로 지점별 속도 변동성과 교통사고 분석을 통해 안전성을 평가하였고 분석 결과의 시사점 을 바탕으로 지하도로 속도 관리 전략을 설계하였다. 먼저, VDS 검지기 지점별 속도 표준편차와 time-varying-volatility 산출 및 속도의 변동성과 교통사고 데이터 매칭을 통해 사고 개연성과 심각도를 분석하였다. 이후, 사후검정을 통해 속 도 및 속도 변동성 기준으로 동질적 부분집합을 도출하고 회귀분석을 통해 속도 변동성과 교통량·밀도 간의 관계를 규명 하여 속도 변동성을 최소화할 수 있는 최적의 교통량과 밀도를 산출하였다. 분석 결과, 속도 변동성이 큰 구간에서 사고 개연성과 심각도가 높게 나타났으며 지하도로에 구간단속을 적용할 경우 하류부에서 변동성이 증가하는 현상을 확인하 였다. 이를 바탕으로 위험 구간을 식별하고 해당 구간에 가변형 속도 제한 시스템을 적용한 로컬 속도 관리 전략을 제시 하였다. 본 연구의 결과는 지하도로의 사고 예방 및 안전성 향상을 위한 실질적인 속도 관리 전략 설계에 기여할 수 있 을 것으로 기대된다.

Proper Orthogonal Decomposition (POD) is applied to analyze the coherent structure of three-dimensional cylinder wake flow. The flow field data, such as velocity and pressure as functions of time, was obtained by the incompressible CFD analysis. The resulting CFD data was then used to determine eigenvalues, POD modes, and time coefficients through POD process. The flow field was approximately reconstructed using some of lower POD modes. The three-dimensional field reconstructed using the low-order model was found to be in good agreement with the original. This verifies that low-dimensional modeling of complex flow fields is fully possible.

Toilet liquid-type cleaners utilize operating technology that employs buoyancy mechanism to inject uniform amount of cleaning solution. Flow characteristics of velocity and pressure distributions in the flow field of toilet flush cleaner injection device have been analyzed with CFD method. The flow rate decreases near the inlet of the system, where it contacts the container of the cleaning liquid bottle. It then increases near the injection device stopper and decreases again as it moves toward the system outlet The height of the cleaning solution decreases from 12 cm to 3 cm when using the spray device, the average outlet velocity decreases by approximately 73%. The solution level difference increases from 1.616 cm to 3.216 cm, the inlet velocity decreases by approximately 4.1%~5.6%. These predicted results can be widely applied as basic conceptual design data for highly efficient toilet flush cleaner injection device.

In order to understand the MR fluid flow in the MR damper core, the annular orifice path was simplified into a square channel and the electromagnetic flow was analyzed. For this purpose, the CFD-ACE+ program was used. The temperature and magnetic field of the MR fluid were based on room temperature and orifice wall data, and 2-D steady incompressible laminar flow was assumed. The inlet and outlet of the orifice channel are at atmospheric pressure, and the inflow velocity of the MR fluid is 0.1 m/s. After analyzing the magnetic field of the core, which is a simple model of the 1 stage MR damper, the electromagnetic flow analysis of the MR fluid flowing through the orifice channel was performed. From this, the magnetic field of the orifice channel and the electromagnetic flow of the MR fluid were observed. As the magnetic flux density increased, the flow distribution and velocity of the MR fluid in the channel core changed significantly.

In the development of a digital multi-process welding machine, we aimed to analyze the heat dissipation effects resulting from changes in the transformer's shape. Two installation configurations for the transformer, vertical and horizontal, were proposed. Thermal-flow analysis was conducted for the welding machine, taking into account variations in spacing between each proposed configuration. The results indicated that the shape and spacing of the components did not significantly alter the airflow around the reactor coil, which is the main heat-generating component of the machine. When comparing the heat dissipation effects across models with different transformer spacings, it was observed that models with narrower spacing exhibited improved heat dissipation, while the vertical configuration demonstrated a slightly higher heat dissipation effect overall. Transient analysis revealed the irregularities in internal flow and the resulting scattered temperature distribution over time within the welding machine.

As the importance of the indoor environment increases. As part of a study to improve range hood performance, a flow analysis of chamber casing was conducted. flow analysis was performed by applying Realizable (  ) Model. For flow analysis, “STAR-CCM+” program of “SIEMENS” was used. It was analyzed how changes in inlet velocity, outlet velocity(flow rate) and static pressure increase occur according to changes in the shape of the chamber casing. Flow analysis was performed by changing the shape of the chamber casing limitedly, but the results were not helpful in improving the performance of range hood.

In this study, flow analysis was performed using ANSYS CFX to evaluate the performance of the 30kg hydrogen fuel cell hexa-copter drone in hovering flight. In the case of a hydrogen fuel cell hexa-copter drone, a total of four cooling fans are mounted on the drone's body in two pairs on the left and right to cool the fuel cell module. In order to evaluate the effect of the air flow from the cooling fan on the aerodynamic properties of the hydrogen fuel cell drone as the mounted cooling fan operates, the change in thrust for the case where the cooling fan operates and does not operate was compared and analyzed. Looking at the analysis results, it was found that the presence or absence of the drone's cooling fan had little effect on the drone's thrust through the thrust results for the six wings.

선박용 연료전지 시스템의 스택 온도를 일정하게 유지하기 위한 스택 냉각 시스템은 Close-Loop의 청수 라인과 Open-loop의 해수 라인을 적절하게 조합하여 구성할 수 있다. 청수와 해수의 열 교환량은 스택 냉각 시스템에 설치된 3-way 밸브의 열림 정도로 결 정된다. 냉각 시스템의 청수 라인과 해수 라인 각각의 펌프 토출량과 3-way 밸브의 열림률 관계는 명확하게 규명하기 어려우며, 동시 에 연료전지 스택과 결합 되어 동작하기 때문에 난해한 거동을 보인다. 본 연구에서는 냉각 시스템의 구성 요소들과 연료전지 스택이 결합 되어 동작할 때의 관계를 해석하기 위해 통계적 기법을 적용하였으며 필요 데이터를 확보하기 위해 청수 라인과 해수 라인으로 구성된 30KW 급 PEMFC 시스템을 모델링하고, 다양한 조건으로 시뮬레이션하였다. 펌프의 토출량 변화, 부하 조건의 변동 등의 다양 한 시나리오를 통해 도출된 파라미터들은 3-way 밸브 열림률, 시스템 효율, 동적 응답성 등이며 각각 축 재정의, 정규화 기법 등 통계 적 기법으로 시각화되었다. 따라서 본 연구의 접근 방식을 이용하면, 결합 된 설비들의 관계를 시각적 데이터로 명확하게 확인할 수 있으며, 가동 조건을 변경했을 때의 시스템 효율, 소모전력, 시스템의 정상 작동 여부를 예측할 수 있다. 또한, 이와 같은 방법은 복잡 한 시스템의 특성을 정의하는 기초 연구로서 의미가 있으며 선박의 빅데이터를 처리하는 연구 등으로의 발전 가능성을 확인하였다.

고속도로 터널 구간은 일반 도로에 비해 사고 발생 빈도와 심각도가 높으며, 특히 터널 내에서 발생하는 사고나 공사와 같은 돌발 상황은 대기 행렬을 유발해 후미 추돌 위험을 증가시킨다. 본 연구에서는 운전자가 돌발 상황 지점에 접근할 때 선제적으로 대응할 수 있도록, Driving Simulator를 활용하여 다양한 정보를 제공하는 터널 내 교통관리 시스템의 효과를 분석하였다. 분석 대상은 차로 변 경 유도, 속도 감소 유도, 돌발 상황 안내로 구성된 세 가지 교통관리 시스템의 개별 효과와 이들의 통합 운영이 터널의 안전성과 운 영 효율성에 미치는 영향을 포함하였다. 분석 결과, 세 가지 교통관리 시스템을 통해 터널 내 평균 통행 속도가 증가하였으며, 돌발 상황 발생 지점에서 차량의 차로 변경과 감속이 선제적으로 이루어지고 급감속 횟수가 현저히 감소하였다. 본 연구는 터널 내 돌발 상황 발생 시 다양한 정보를 제공함으로써 터널의 안전성과 교통흐름을 개선할 수 있음을 입증하였으며, 특히 여러 시스템을 통합적 으로 운영할 때 그 효과가 극대화됨을 Surrogate Safety Measure를 통해 확인하였다. 이러한 결과는 향후 터널 교통관리에서 단일 시스 템의 기능만을 고려하기보다는, 다양한 교통관리 시스템 간 상호작용을 고려해야 함을 시사한다.

서울시의 대표적인 대중교통 수단인 도시철도를 이용하는 승객 수는 지속적으로 증가하고 있다. 이에 따라 출 퇴근시간대에 열차 내의 혼잡뿐만 아니라 역사내의 혼잡까지 이어져 안전사고가 발생하기도 한다. 본 연구는 역사에서 발생되는 보행흐름의 위험 여부를 판단하기 위해 도로의 교통류에서 활용되고 있는 vehicle accumulation과 travel time 간의 elliptic bivarate relationship을 적용하였다. 또한 보행흐름과 교통류의 혼잡발생 과정을 비교하여 차이점을 규명하였다. 본 연구에서는 도시철도 역사내 CCTV영상을 기반으로 실제 데 이터를 추출하여 역사내 통로에 발생하는 여러 보행흐름을 혼잡강도와 혼잡지속도에 따라 분류하여 비교분석하였다. 혼잡이 발생하는 여러 역의 첨두, 비첨두, 주말등 다양한 시간대의 CCTV 영상을 확보하였고, ByteTrack 방식을 활용하여 객체를 검지하였다. 검지된 보 행흐름을 강도, 지속도에 따라 분류하고 보행 누적량과 평균통행시간을 산출하여 비교분석하였다. 또한, elliptic bivarate relationship의 형태가 교통류와는 어떠한 차이점이 있는지를 규명하고 보행에서의 위험 상황 여부를 그래프를 통해 확인하였다. 분석 결과, 혼잡발생 강도가 높을수록 그래프 타원의 장축이 길게 나타났고, 보도유효폭이 클수록 타원의 기울기가 낮게 나타났다. 또한, 사람들의 평균보 행속도가 클수록 타원이 낮게 위치하였다. 마지막으로 흐름이 바로 해소되지 않고 지속되는 보행흐름의 경우, 일반적인 타원형태에서 우측부분에 타원이 추가로 형성됨을 확인하였다. 교통류와 비교한 결과, 차량의 경우 교통량에 따라 속도가 일정하게 나타나지만, 보 행의 경우 보행량과 속도의 관계가 비교적 불분명하였다.

Air flow field characteristics in a compact chamber system are indispensable for the efficient development of vehicle aerodynamic performance. In this study, air flow and velocity uniformity in the chamber system were numerically analyzed using the CFD method. Air flows at a uniform velocity from the outlet of the blower, passes fast through the heat exchanger with partial pressure difference, and then moves into the blower inlet. Overall pressure drop through the fan gradually increases with the flow rate. The uniformity varies along the test section, decreasing by 5-10% with distance from the nozzle. These predicted results can be widely used as basic conceptual design data for an efficient vehicle chamber system.

In this study, a numerical analysis study was conducted on the flow characteristics according to the internal flow path change and differential pressure of the hydrogen shut-off valve, and through this, the pressure loss characteristics and flow coefficient of the hydrogen shut-off valve were predicted. ANSYS CFX program was used to predict the flow characteristics of the hydrogen shut-off valve. When the flow path gap was 1.3 mm, the design conditions of the hydrogen shut-off valve were satisfied, and the value of the flow coefficient of the valve was about 1.53. As the inlet pressure of the hydrogen shut-off valve increases, the outlet flow rate increases, but regardless of the inlet pressure, the flow coefficient of the valve is almost constant, ranging from 1.53 to 1.56, indicating that it is the inherent flow coefficient of the designed hydrogen shut-off valve.

Passengers on public buses operating in the metropolitan area are exposed to the closed indoor air for minutes to hours. The indoor air quality of buses is mostly controlled through ceiling-mounted ventilation and filtration devices. A simulation study using a commercial code was conducted for fluid flow analysis to evaluate the potential effectiveness of an air purifier that can be inserted into bus windows to supply clean air from the outside to the inside. As a result of field measurements, the average CO2 concentration inside the bus during morning and evening rush hours ranged from 2,106±309 ppm to 3,308 ± 255 ppm depending on the number of passengers on board. This exceeded the Guideline for Public Transportation. The optimal installation position of an air purifier appeared to be the front side of the bus. In fact, even a low diffusing flow velocity of 0.5m/s was effective enough to maintain a low concentration of CO2 throughout the indoor space. Based on numerical analysis predictions with 45 passengers on board, the maximum CO2 concentration in the breathing zone was 2,203 ppm with the operation of an air purifier.

Nuclear power generation is expected to be enlarged for domestic electricity supply based on the 10th Basic Plan of Long-Term Electricity Supply and Demand. However, the issues on the disposal of spent nuclear fuel or high-level radioactive waste has not been solved. KBS-3 concept of the deep geological disposal and pyroprocessing has been investigated as options for disposal and treatment way of spent nuclear fuel. In other way, the radionuclide management process with 6 scenarios are devised combining chlorination treatment and alternative disposal methods for the efficient disposal of spent nuclear fuel. Various scenarios will be considered and comprehensively optimized by evaluation on many aspects, such as waste quantity, radiotoxicity, economy and so on. Level 0 to 4 were identified with the specialized nuclide groups: Level 0 (NFBC, Hull), Level 1 (Long-lived, volatile nuclides), Level 2 (High heat emitting nuclides), Level 3 (TRU/RE), Level 4 (U). The 6 options (Op.1 to 6) were proposed with the differences between scenarios, for examples, phase types of wastes, the isolated nuclide groups, chlorination process sequences. Op.1 adopts Level 0 and 1 to separate I, Tc, Se, C, Cs nuclides which are major concerns for long-term disposal through heat treatment. The rest of spent nuclear fuel will be disposed as oxide form itself. Op.2 contains Sr separation process using chlorination by MgCl2 and precipitation by K2CO3to alleviate the burden of heat after heat treatment process. U/TRU/RE will be remained and disposed in oxide form. Op.3 is set to pyroprocessing as reference method, but residual TRU/RE chlroides after electrorefining will be recovered as precipitates by K3PO4. Op.4 introduces NH4Cl to chlorinate TRU/RE from oxides after Op.2 applied and precipitates them. TRU/RE/Sr will be simultaneously chlorinated by NH4Cl without MgCl2 in Op.5. Then, chlorinated Sr and TRU/RE groups will be separated by post-chlorination process for disposal. But, chlorinated Sr and TRU/RE are designed not to be divided in disposal steps in Op.6. In this study, the mass flow analysis of radionuclide management process scenarios with updated process variables are performed. The amount and composition of wastes by types will be addressed in detail.

In general, systems are developed by repeatedly performing the processes of design, analysis, manufacturing, and performance testing. In particular, systems with temperature, pressure, and flow rate often utilize computational fluid dynamics tools at the design stage. In this paper, we aim to verify the reliability of the analysis results of Solidworks Flow Simulation, which is widely used in heat flow analysis at the design stage. A tube furnace was manufactured, various experiments were performed, and a study was conducted to compare the analysis results. The details of the experiment are as follows. First, an experiment was conducted in which the heater was heated to 900°C without insulating the exposed part of the tube. The detailed contents of the experiment are as follows; - Heating heater and measuring temperature without supplying flow inside the tube, - Tube flow supply (25°C, 15 lpm air) and heater heating/temperature measurement. Second, an experiment was performed in which the exposed part of the tube was insulated (thickness 50 mm) and the heater was heated to 900°C. The detailed contents of the experiment are as follows; - Insulate the outside of the tube except for the flanges at both ends of the tube, and heat the heater and measure the temperature without supplying flow inside the tube. - Insulate the outside of the tube except for the flanges at both ends of the tube, supply flow rate inside the tube (25°C, 15 lpm air) and measure heater heating/temperature. - Insulate the flange of the flow supply section, heat the heater and measure temperature without supplying flow inside the tube. - Insulate the flange of the flow supply section, heat the supply air (277°C, 15 lpm) and measure the temperature using a heating gun without heating the heater. - Insulate the flange of the flow supply section, supply heated air (277°C, 15 lpm) and measure heater heating/temperature. - Insulate the flange of the flow supply section and measure temperature according to heater heating (900°C) and supply temperature (25°C, 277°C 15 lpm). The following results were derived from the experimental and analysis results. - When the exposed part of the tube is insulated, the temperature inside the tube increases and the steady-state power decreases compared to non-insulated. - In areas with insulation, the temperature error between experiment and analysis results is not large. - When flow rate is supplied, there is a large temperature error in experiment and analysis results. - The temperature change after the center of the heater is not large for a temperature change of 15 lpm flow rate. From these results, it can be seen that Solidworks Flow Simulation has a significant difference from the experimental results when there is a flow rate in the tube. This was thought to be because the flow rate acts as a disturbance, and this cannot be sufficiently accounted for in the analysis. In the future, we plan to check whether there is a way to solve this problem.