In order to design a diesel engine system and predict its performance, it is necessary to analyze the gas flow of the intake and exhaust system. A gas flow analysis in three-dimensional (3D) format needs a high-resolution workstation and enormous time for analysis. Therefore, the method of characteristics (MOC) was used for a gas flow analysis with a fast calculation time and a low-resolution workstation. An experiment was conducted on a single cylinder diesel engine to measure pressure in cylinder, intake pipe and exhaust pipe. The one-dimensional (1D) gas flow was analyzed under the same conditions as the experiment. The engine speed, valve timing and compression ratio were the same conditions and the intake pressure was inputted as the experimental results. Bent pipe such as an exhaust port that cannot be realized in 1D was omitted. As results of validation, the cylinder pressure showed accuracy, but the exhaust pipe pressure exhibited inaccuracy. This is considered as an error caused by the failure to implement a bent pipe such as an exhaust port. When analyzed in 3D, calculation time required 61 hours more based on a model of this study. In the future, we intend to implement a bent pipe that cannot be realized in 1D using 3D and prepare a method to supplement reliability by using 1D-3D coupling.

Various electronic control parts and devices installed in electric vehicles have greatly improved the convenience of occupants, but electromagnetic waves emitted from electronic devices have greatly increased concerns about malfunctions, deterioration of performance, safety accidents, etc. There are two models of analysis. Case A is symmetrical about one axis of rotation. Case B has two axes of rotation. In this study, a flow analysis was conducted to find excellent flow conditions in the mixing process to develop a paint with excellent electromagnetic shielding and thermal insulation performance. The results of the flow analysis are reflected in manufacturing specifications and are intended to be used to develop high-quality systems.

In this study, two types of cyclone separators containing a structure of prevention underflow and a cyclone separator without the structure were analyzed by computational fluid technique. The pressure loss was increased by increasing the inlet velocity from 8m/s to 28m/s, and the velocity and pressure were compared through five cross sections in the vortex finder. Also, the velocity and the pressure contour in the central section were compared. It can be seen that the performance reduction of the cyclone separator by the prevention structure is related to the distance to the vortex finder inlet rather than the effect of the diameter of the structure.

In this study, numerical analysis was carried out to develop low-noise axial fans, which are often used for ventilation in houses. A commercial program and the turbulence models are used for the analysis of internal fan. Proudman acoustic power model and the Curle surface acoustic power model were used for analysis. As a result, the distribution of flow velocity and pressure around the blade and guide of the fan was high, and low in the center of the fan. Noise from the inner wall of the fan case and the blade surface was the highest at the body and vane connections of the blade, and low at the center of the vane and the center of the body.

The flow analysis of two dimensional transient flow over the obstacles with rectangular cross sections was performed. And 190 velocity distributions for each aspect ratio were imaged to provide input data for convolutional neural network learning. The classification and regression methods were used in estimating the aspect ratio from given velocity distributions. As a result the classification method was more exact than the regression method. But both the classification and regression methods gave relatively accurate prediction of the defined aspect ratio judging from the imaged velocity distributions. This confirms that the deep learning technique is applicable to the flow analysis.

겨울철 벤로형 유리온실(W59×L68×H5.9m) 보온스크린 높이의 차이에 따른 실내온도 변화를 파악하기 위하여 00시부터 04시까지 30분 간격으로 열유동해석을 하였다. 초기에는 상대적으로 난방 외부접촉면적이 큰 보온스크린 설치높이 5.9m에서 보온스크린 설치높이 4.1m에 비해 온도감소가 빨라 낮은 온도를 나타냈으나 해석 2시간 이후부터는 상대적으로 온도감소가 느렸고 04시에는 0.6°C 높았다. 그러나 해석시작 1시간 후 실내온도가 약 13°C까지 내려가고, 그 이전에 난방기가 작동해야 된다고 볼 때, 해석 2시간 동안 온도감소가 상대적으로 느렸던 보온스크린 설치높이 4.1m에서 5.1m에 비해 난방에너지 절감에 유리할 것으로 판단되었다. 토마토가 자라는 지면 2m 높이에서의 유동은 보온스크린 설치높이 5.9m에서 4.1m에 비해 상대적으로 넓고 빨랐으며 유동해석 1시간 후인 01시의 평균차이는 0.034m·s-1였다. 여름철 차광스크린 설치높이를 5.7m와 3.9m로 달리하되 70%닫힘 조건에서 12시부터 13시까지는 온실하부덕트 외부 공기유입량 0.67m3·s-1 상태 그 후부터는 외부 유입공기를 3배로 증가하여 냉방효과를 비교하였다. 초기 12시부터 13시까지는 차광스크린 70%닫힘 상태에서 무차광에 비해 오히려 평균 약 0.9°C 높았지만 외부공기유입량이 증가하는 13시 이후 부터는 차광스크린 70%닫힘 조건에서 온도가 감소하였고 14시 30분에는 무차광에 비해 0.5°C 낮았다. 차광스크린 70% 닫힘 조건에서 바닥면의 온도분포는 스크린 설치높이와 개방 정도에 비례하여 낮았으며 무차광에 비해 8°C이상 낮았다. 온실 내 상대습도는 차광스크린을 30% 개방하는 조건에서는 차광스크린의 높이나 개방정도에 따른 차이가 미미하였다.

본 연구에서는 대면적을 지니는 CDI 모듈의 흐름 향상을 위하여 유체가 들어가는 유입구로부터 면적이 증가하는 직사각형 형태의 유로를 설계하였다. 이를 바탕으로 설계된 모듈 형태에 대해 공급수의 흐름성과 사영역의 유무를 파악하였고 CFD 전산 유체 역학 프로그램을 통해 유로 내의 내부 압력, 유선 그리고 속도 벡터 분포를 분석하였으며 실제 흐름 관측과 CFD 프로그램을 비교 분석하였다. 실험 결과 모든 유속 10, 20, 30 mL/min에서 유로 내 사영역이 거의 발생하지 않았으며 공급수의 흐름성도 일정하게 유지되어 추후 대면적을 가지는 CDI 공정에 적용이 가능할 것이라 판단된다.

Angiography has excellent advantages to visually observe the internal morphology of the stenosed blood vessel. For OCT(Optical coherence tomography), it is possible to directly provide a reliable two-dimensional cross-sectional information as compared to conventional angiography. In the present study, both velocity and wall shear stress distributions were numerically investigated using stenosed blood vessel models (0%, 25%, 50%, and 75% stenotic expansion rate). The blood vessel geometry was prepared based on the human stenotic aorta from OCT image. Commercially available software (CATIA V5) was used to reconstruct 3D blood vessel for numerial analysis. Pulsatile blood flow boundary condition was applied. The numerical study could help our understanding of the hemodynamic differences in a stenosed blood vessel.

In the modern industrial period, the introduction of mass production was most important progress in civilization. Die-casting process is one of main methods for mass production in the modern industry. The aluminum die-casting in the mold filling process is very complicated where flow momentum is the high velocity of the liquid metal. Actually, it is almost impossible in complex parts exactly to figure the mold filling performance out with the experimental knowledge. The aluminum die-castings are important processes in the automotive industry to produce the lightweight automobile bodies. Due to this condition, the simulation is going to be more critical role in the design procedure. Simulation can give the best solution of a casting system and also enhance the casting quality. The cost and time savings of the casting layout design are the most advantage of Computer Aided Engineering (CAE).. Generally, the relations of casting conditions such as injection system, gate system, and cooling system should be considered when designing the casting layout. Due to the various relative matters of the above conditions, product defects such as defect extent and location are significantly difference. In this research by using the simulation software (AnyCasting), CAE simulation was conducted with three layout designs to find out the best alternative for the casting layout design of an automotive Oil Pan_BJ3E. In order to apply the simulation results into the production die-casting mold, they were analyzed and compared carefully. Internal porosities which are caused by air entrapments during the filling process were predicted and also the results of three models were compared with the modifications of the gate system and overflows. Internal porosities which are occurred during the solidification process are predicted with the solidification analysis. And also the results of the modified gate system are compared.

This study was successfully achieved out the optimized system for dispersing and mixing condition of resin liquid. The flow analysis was simulated according to the shape of the impeller and the stirring tank using ANSYS software and optimized in advanced design. As a result, it was confirmed that the shape and double number of the impeller on the flow field are influenced better effects in a range of mixing and diffusion areas comparing to single number of impeller. It was considered that stirring was performed more quickly and efficiently under the condition of double numbers and saw tooth type impeller. This result can be applied practically for the mixing tank in the industrial application and avaliable used to make a new system for painting equipment.

잠수함에서 발생하는 수중방사소음은 적함의 소나에 의해 피탐될 확률과 직결되며, 잠수함 저소음화 방안은 생존성 향상을 위해 필수적이다. 최신 잠수함의 경우 기계류 소음저감 및 고속/대형화가 진행됨에 따라 선체 주위에 발생하는 유동소음에 대한 관심이 높아지고 있다. 본 연구에서는 자유수면의 효과를 고려하여 잠수함 형상 주위에 발생하는 유동소음 수준을 예측할 수 있는 소음해석기법을 개발하였다. 잠수함이 자유수면 근처 운항시에 잠수함 주위 유동장의 교란에 의해 발생하는 난류유동소음과 쇄파버블에 의한 소음이 발생한다. 먼저 잠수함 주위 유동장 해석을 위해, VOF법 기반의 비압축성 이상유동(two-phase flow)해석을 수행하여 잠수함 주위 자유수면 형상과 유동장 정보를 도출하였다. 이후 난류유동소음해석을 위해 음향상사기법인 Permeable FW-H를 적용하였고, 쇄파버블 소음해석을 위해 유동해석에서 도출된 난류운동에너지 분포결과를 기반으로 쇄파버블 소음모델을 적용하였다. 최종적으로 개발된 유동소음 해석기법은 선박해양플랜트연구소(KRISO)의 대형캐비테이션터널(LCT)에서 수행된 잠수함 모형 유동소음계측 실험결과와 비교를 통해 검증을 수행하였다.

This study investigates the enhancement of the oxygen diffusion rate in the cathode channel of a proton exchange membrane fuel cell (PEMFC) by pure oscillating flow, which is the same as the mechanism of human breathe. Three-dimensional numerical simulation, which has the full model of the fuel cell including electrochemical reaction, ion and electronic conduction, mass transfer and thermal variation and so on, is performed to show the phenomena in the channel at the case of a steady state. This model could analysis the oscillating flow as a moving mesh calculation coupled with electrochemical reaction on the catalyst layer, however, it needs a lot of calculation time for each case. The two dimensional numerical simulation has carried on for the study of oscillating flow effect in the cathode channel of PEMFC in order to reduce the calculation time. This study shows the diffusion rate of the oxygen increased and the emission rate of the water vapor increased in the channel by oscillating flow without any forced flow.

Numerical analysis has been carried out to investigate seawater flow field characteristics with various current directions near the manganese nodule mining device. Seawater flow near the collecting device is largely influenced by the sea current direction, especially along the downstream of the rear system. Predicted flow velocity distributions are analyzed with turbulent kinetic energy and drag force. There is big flow field variation when the direction angle between the mining device and seawater current flow approaches to 30°~ 120°, and flow velocity along the rear region of 60° becomes faster than 180°. Averaged turbulent kinetic energy at 180° also becomes low, about 57% higher at 60°. These results from the study can be applicable to the optimum design of manganese nodule collecting system in the deep seawater flow.