Earticle

노인인구비율의 증가에 따라 노인의료복지시설의 수 또한 증가하였으나 노인의료복지시설의 실내공기질을 확보할 수 있는 연구는 미흡한 실정이다. 이에 본 연구에서는 노인의료복지시설의 취기로 인한 실내공기오염과 오염물질확산특성을 조사하여 노인의료복지시설에 적합한 공조설비 및 환기지침 개발에 필요한 기초자료를 확보하고자 한다. 연구결과 노인의 안전성을 위해 출입문이 닫을 경우나 겨울철같이 노인의 온열불쾌감으로 인해 창문개방을 하지 못 할 경우에는 창문개방을 한 경우보다 약 2배가량 취기강도가 높을 뿐만 아니라 더 오래 동안 오염물질이 실내에 체류하게 된다. 그리고 개구부 개방을 통한 환기를 실시하더라도 실의 형상과 급기구와 개구부의 위치에 따라 실내오염물질의 제거효과가 미미할 수 있었다. 그러므로 노인의료복지시설의 쾌적한 실내공기질 및 안정적인 오염물질제거를 위해서 노인의료복지시설에 적합한 환기설비가 개발될 필요성이 있다고 판단되었다.

As the population of the elders are increasing, the healthcare facilities for the aged have been increasing, but there is a lack of studies on air quality securement for the healthcare facilities for the aged. Thus, this study aimed at researching on the pollutant diffusion characteristics of the air pollution at the healthcare facilities for the aged, and securing the fundamental data that is needed for the suitable facility installation and ventilation guideline development. According to the results, in case of closing the doorways for the safety of the elders or when the windows can not be opened in the winter for thermal displeasure of the elders, the concentration of bad odor was twice the case when the windows were opened, and the pollutants stayed inside longer. Even if the ventilation was done via opened windows, removal of the indoors pollutants may be insignificant depending on the forms and locations of the air supplier and the opening area. The results of this study showed that there is a need for proper ventilation system, which is for prevention of secondary pollution and stable removal of the pollution in the healthcare facilities for the aged.

The objective of this study was to determine the optimal angle of a wind louver that would induce the optimal wind speed for indoor. Being controlled to have an optimized angle depending on the direction from which wind is blowing and the wind speed, the wind louver to be installed on the building envelop comes to create indoor comfort through a constant wind speed using the function that reduces the indoor wind speed by changing the angle when the wind speed is not lower than a certain level and makes wind flow into the room to the maximum when the wind direction is adverse to catching the wind or the wind speed is not higher than a certain level. To determine the optimal wind louver angle, a core-centered office building with cross-ventilation problems in the climate of Seoul, Korea, which experiences four distinct seasons, was considered for analysis in this study. A module 1 office space model was used for the CFD simulation to analyze the average indoor wind speed with respect to the outdoor wind speed (varied between 1 and 8 m/s), the wind louver angle, and the outdoor wind direction (varied between $0^{\circ}$ and $180^{\circ}$ in steps of $10^{\circ}$).

본 연구는 Abaqus의 CFD-Structural Co-Simulation 기법을 활용하여 아파트 화재 시뮬레이션을 수행하고, 화재로 인한 연 기 확산 경향과 더불어 주요 구조 부재의 열-응력 및 변형을 동시에 분석하는 연구의 가능성을 타진하였다. 해당 해석 기법을 통해 화재 시의 열-유체 유동이 구조물에 미치는 열 하중을 전달하고, 이로 인한 구조적 응답을 계산할 수 있어 통합적인 화재 안전성 평가에 필수적이다. 또한 해석의 효율성을 극대화하고 빠른 결과를 도출함으로써, 환기시스템의 운영 변화(배기 용량, 위치 등)에 따른 연기 배출 효율 경향 및 구조물의 열적 안전성 변화 경향을 신속하게 파악하는 데 중점을 두었다. 시뮬레이션 결과는 피난 안전성(가시거리, 온도)과 구조적 안정성 (최대 응력, 변형률) 두 가지 측면에서 분석되었으며, 이를 통해 건축 초기 단계에서 방재 설계의 효율성과 타당성을 검토하는 데 기여하는 방법론적 기반을 제시하고자 한다.

Thermoacoustic oscillations (TAOs) could be often observed in liquid helium cryogenic system especially in half-open tubes. These tubes have closed warm end (300K) and open cold end (usually 4.4K). This phenomenon significantly induces additional heat load to cryogenic system and other undesirable effects. This work focuses on using computational fluid dynamics (CFD) method to study TAOs in liquid helium. The calculated physical model, numerical scheme and algorithm, and wall boundary conditions were introduced. The simulation results of onset process of thermoacoustic oscillations were presented and analyzed. In addition, other important characteristics including phase relation and frequency were studied. Moreover, comparisons between experiments and the CFD simulations were made, which demonstrated thevalidity of CFD simulation. CFD simulation can give us a better understanding of onset mechanism of TAOs and nonlinear characteristics in liquid helium cryogenic system.

인공습지는 오염물질 저감기능을 포함하는 여러 가지 생태서비스 기능 때문에 다양하게 적용되고 있다. 그러나 인공습 지에 많은 입자상 물질이 유입하게 되면 유지관리의 어려움과 기능의 저하를 초래한다. 따라서 본 연구는 인공습지 내 입자상 물질의 제거효율 향상을 위한 침강지내 최적 baffle 설치방안을 도출하고자 수행되었다. 최적 저류판 설치방안 은 침강지내 유체와 입자의 흐름을 해석함으로써 도출가능하며, 이를 위해 전산유체역학(Computational Fluid Dynamics, CFD) 이론을 활용하였다. 연구결과는 baffle이 유속을 저하시키고 입자상 물질의 침강효율을 증가시키는 것으로 나타났으며, 경사각을 가진 저류판보다는 수직 저류판이 효과적인 것으로 나타났다. 이러한 연구결과를 활용하 여 공공지역 비점오염저감시설로 설치된 소규모 하이브리드 인공습지의 침강지 효율개선 방안을 도출하였다. 수직각을 이용한 저류판을 설치할 경우 침강효율이 1.2~1.3배 정도 증가하는 것으로 나타났다. 이러한 침강지 내 저류판의 설치 에 따른 결과는 인공습지의 전반적인 저감 효율을 증가시킬 뿐만 아니라 유지관리 빈도를 줄임으로써 비용효율적 인공 습지 설계에 기여할 것으로 평가된다.

Constructed wetlands are widely applied in urban and rural areas for various purposes such as pollutants reduction, acquisition of eco-spaces and habitats, flooding reduction, acquisition of water resources and environmental education. Since the design of constructed wetlands utilizes ecosystems, special consideration must be given to ecological mechanisms, environmental mechanisms and hydrological mechanisms. To ensure the sustainable functionality of constructed wetlands, it is necessary to achieve stable flow rate and velocity, and remove sediments to ensure sufficient space for detention. To enhance the efficiency of constructed wetland sedimentation basins, this study determined the optimal position for baffle installation, and applied Computational Fluid Dynamics (CFD) to the cross-sectional design of wetlands. CFD analysis revealed that the decrease in flow velocity with baffle installation enhanced the efficiency of sedimentation of particulate matters. Vertical baffles had higher sedimentation efficiency than those with an inclined angle. When vertical baffles were installed in the sedimentation basin of a hybrid constructed wetland to reduce non-point source pollutants in urban areas, the average flow velocity within the basin decreased by 10~30%, while the sedimentation efficiency improved by 1.3~1.5 times. The application of CFD to constructed wetlands is expected to improve the cost efficiency of designing hybrid constructed wetlands with high removal efficiency.

Computational fluid dynamic simulation based on the ABAQUS software was conducted to observe the inside flow of slot-die nozzle. The slot-die nozzle was modeled as 3-dimensional structure and three significant parameters were determined: inlet velocity of fluid, reservoir angles, number of strips none of which have been mentioned previously in the literature. The design of experiment, full factorial analysis was performed within determined design and process levels. The simulation result shows the inlet fluid velocity is most significant factor for the flows of inside nozzle. As an interaction effect, reservoir angle is closely related with number of strip that should address when the nozzle is designed. Moreover, the optimized values of each determined parameter were obtained as 35 mm/s of inlet velocity, 3 of strip numbers, and $22^{\circ}$ of reservoir angles. Based on these parameters, the outlet velocity was obtained as 0.53% of outlet uniformity which is improved from 8.67% of nominal results.

The purpose of this study is to review the reliability of the CFD. To perform this study, CFD simulations were compared with experimental results based on the performance results of the diffuser line. The results of this study are as follows. 1) Looking at the results of indoor air distribution measurements, Air distribution of indoor through Air of diffuser could judge to be distributed of indoor air evenly. 2) It compared actual data of Cooling experimental and heating experimental with the CFD analysis results. the average error rate of Cooling was 6% and the average error rate of Heating was 6.9%. In air flow case, the air velocity is some different to 0m/s ~ 0.178m/s. Looking at the air flow and the air velocity, two results could judge to be similar to pattern. As a result, the predictions of the indoor thermal and airflow environment through CFD simulation are considered possible.

일반 공장 내에서 일어나는 화재 및 폭발의 점화원으로 전기가 차지하는 비율은 17%에 달하 는 것으로 나타났으며 가스시설에서 화염, 고온표면, 고온입자 등 점화원 관리가 철저하다는 점을 감안하면 전기가 전화원으로 될 가능성은 훨씬 높을 것으로 추청된다. 이와 관련된 한국 가스안전공사의 가스시설 방폭기준은 위험구역분류에 관한 기준이 매우 부족한 실정이다. 본 연구에서는 LPG관련 시설의 시설별 방폭구역설정을 위해 가스누출전산유동해석 프로그램인 FLACS를 사용하여 LPG시설에서 가스 누출을 가정한 누출 시뮬레이션을 진행하였다. CFD결 과를 기반으로하여 방폭구역설정 기본 도면을 제시할 수 있을 것으로 기대한다.

The electric is accounted for about 17% as the ignition point in the industries. However, Flame, high temperature surface, high temperature particles are thoroughly treated in the gas facilities. Therefore, The electric will be more dangerous substance in the gas facilities. So, facilities where use flammable and explosive gas must distinguish the hazardous area for example zone 0, 1, 2. However, there are lack of detailed standard about hazardous area classifications in KGS code which made by Korea gas safety corporation. In this study, Gas leak CFD was conducted by FLACS(GexCon). So, the detailed drawings regarding hazardous area classification of LPG facilities can be expected in this paper.

Through thermal environment measurement and diagnosis of HVAC system, heating condition of the S station building was investigated and problems was grasped from before this study. On the basis of this study, improvement scheme was prepared for improvement of heating condition. In this study, effect of improvement scheme was confirmed for saving energy of the S station building by CFD simulation and saving energy quantity was computed with improvement scheme. Results of this study are as follows. (1) The result of CFD simulation before improvement, heating of low rise space accumulate on a high temperature at high rise space of above 10m hight, thermal environment of 2nd floor area is presented badly. (2) The result of CFD simulation by improvement, the temperature is higher than 22.0℃ which is designed temperature of the S station building but the applied improvement in this CFD simulation was improved for outdoor air restraint in architecturally and attention of management is needed for better heating effect. (3) The result of saving energy quantity, 40.3% reduction can be saved by the case 1 improvement and 65.6% reduction can be saved by the case 2 improvement.

본 연구는 구조/유체 시뮬레이션 분야에서 VR과 AR를 중심으로 시뮬레이션이 활용되는 현장에서 사용성을 분석하고 어떤 장단점이 있는지 연구한다. 1차로 문헌연구를 통해 구조/유체 시뮬레이션 분야에서 VR과AR 기술의 현 황 및 전망 등을 연구하였고 이에 대한 사례조사를 기술하였다. 또한 사용성 평가의 지표가 되는 사용성 연구에 대한 이론적 고찰을 통해 VR과 AR 사용성 평가를 위한 방안을 도출하였다. 2차로 구조/유체 시뮬레이션 분야에서 모바일 기반의 VR과 AR 서비스의 사용성을 조사하기 위해 현장(C사)에서 구조/유체 시뮬레이션을 수행하거나 활용하고 있는 피실험자들을 대상으로 심층 인터뷰를 진행하였다. 본 연구의 결과는 추후 구조/유체 시뮬레이션 분야에서 VR/AR서비 스 구성에 활용될 수 있을 것으로 사료된다.

This study focused on the usability and the difference between VR and AR technology in the FEM/CFD simulation environments. First, this paper explains the current status and prospect of the VR/AR technology and conducted a case study on the VR and AR service in the FEM/CFD simulation environments. In addition, we made the evaluation strategies for usability by a review of previous research. And then, after Interviewers participants who use of simulation at a specific site C to we investigated the usability of the VR and AR service based on the mobile device in the FEM/CFD simulation environments. The result of this study is look forward to be used as a design service to form a VR and AR service in the future.

본 연구에서는 창문의 크기와 위치를 달리하여 정수장 여과지동의 환기특성을 3차원 전산유체역학 프로그램을 이용하여 해석하였다. 그 결과 기존 창문의 위치와 크기를 갖는 여과지동에서 최대 염소가스의 농도는 0.13ppm 으로 나타났다. 이것은 좀 더 쾌적한 실내 공기질을 유지하기 위해서 추가적인 환기량이 필요함을 의미한다. 정 수장 여과지동의 창문의 크기를 2배로 늘리고 재배치한 경우, 실내 염소가스의 최대농도는 0.11ppm으로 감소하 였다. 따라서 정수장 여과지동의 염소가스를 줄이기 위해서 환기량과 환기구 위치가 중요함을 알 수 있었다.

In this paper, the ventilation characteristics of a filter basin of the purification plant were investigated for different windows size and the locations by numerical simulation. It has been found that the maximum concentration of chlorine gas in the filter basin with original windows was predicted about 0.13ppm. It means that an additional required amount of ventilation is needed to maintain good indoor air quality. For the filter basin with double sized windows and relocations, the maximum concentration of chlorine gas was predicted 0.11ppm. It is known that the window size and its locations in a filter basin of the purification plant are important factors to reduce the concentration of chlorine gas in the indoor.

본 연구에서는 비용효율적인 인공습지의 설계를 위하여 초기 침강지 내 다양한 도류벽형태에 따른 인공습지의 사수역 및 입자상 물질의 제거효율을 전산유체역학(Computational Fluid Dynamics, CFD)을 통해 연구하였다. 그 결과, 초기 침강지에서 도류벽의 형태는 유입 유속에 영향을 미치며, 침전률에도 큰 영향을 미치는 것으로 분석되었다. 2 ㎛ 와 5 ㎛ 와 같은 미세한 입자에서는 수평으로 설치한 도류벽에서 침전률이 높았으며, 10 ㎛ 와 20 ㎛ 크기의 큰 입자는 수직형 도류벽에서도 높은 침전률을 나타내었다. 또한, 수직형 도류벽의 경우 좁은 면적에 침전이 집중적으로 이루어지기에 다른 형태에 비해 유지관리가 효율적일 것으로 판단되었다. 이에 인공습지의 설계 목적에 따라 가장 적절한 도류벽의 형태를 선정하여 설계해야 할 것으로 보여진다.

In this study, the removal efficiency of the wetland in terms of particulate matter and dead water zone through the application of baffles in the sedimentation were simulated with the use of Computational Fluid Dynamics (CFD) to determine the design of a cost-effective constructed wetland. As a result, it was analyzed that the application of the baffle in the sedimentation tank affect the flow and sedimentation rate. Fine particles such as 2 ㎛ and 5 ㎛ showed high sedimentation rate when the baffles are installed horizontally. large particles such as 10 ㎛ and 20 ㎛ showed also high deposition rate when the baffles are installed vertically. In addition, the vertical baffles is considered to be more efficient than other baffle types in terms of maintenance since the particulate matter are concentrated in narrow areas. Therefore, it is considered that the selection of the most applicable type of baffle depends on the design purpose of the wetland to be constructed.

Using jet propulsion, squid can swim at high speed or at low speed with good maneuverability, which makes them quiet valuable to be studied for biomimetic purposes. Vortex rings usually occur in the highly-unsteady jet flow in squid, and they play quite important roles in the jet propulsion of squid. This paper tries to investigate the squid jet structure by computational fluid dynamics (CFD) analysis. A simplified squid body model was established. The mantle motion during jet locomotion was explicitly included into the simulations by using a deforming mesh. By solving the 2D-axisymmetric, incompressible, laminar, unsteady Navier.Stokes equations, different vortex evolution behaviors were observed depending on different mantle contraction velocities and nozzle diameters. An important parameter, the formation number of the vortex rings, L/D, which decide the propulsive efficiency of jet propulsion directly, was also discussed in this paper. The numerical results show that adult squid propel themselves by long jet flows with a large formation number, L/D. The results also prove that smaller squid have larger relative funnel diameter. Interaction of vortex rings was simulated in two jet process, which might interpret squid increase their contraction frequencies with elevated swimming speed. To validate the force generated in the simulation, a bionc squid mantel jet propulsor is investigated and tested.

Temperature increases and air flow stagnation caused by the large temperature variation between the cultivation beds and the close irradiation by artificial lightings in a vertical type plant factory serve as chief factors in the deterioration of crop quality and growth. In preceding researches, the methods to resolve these problems and to improve air flow rate were applied by utilizing air flow devices such as air conditioning devices and external fans. However, enhancing the air flow by an external fan reduces the temperature deviation in the entire area of the facility. To maintain a uniform growth environment, there is a limit in improving air flow, which is locally stagnant. Therefore, the factors that hinder the growth of the crops need to be removed by promoting air flow stagnation near the crops with a simultaneous operation of the inner fans at each cultivation bed. Firstly, CFD simulation process is required because a lot of time and cost are involved to establish a testing environment and cultivation experiment in order to investigate improvement effect of the cultivation environment according to the operation mode of air flow device. Experiment and analysis have to be carried out based on these simulation results. This study attempts a CFD simulation, and compares and analyzes the improvement effect on the growth environment according to the operation mode of air flow devices for the vertical type plant factory. By measuring cultivation environment under the smart environment based on the sensor network, accuracy of simulation result is verified, and effect on the improvement of growth rate is investigated through crop cultivation experiment. Experiment results showed that control condition of Case H wherein internal fans are additionally operated was the most suitable in maintaining set temperature, improving air flow, and growth rate of the crops.

Web based simulation is used in various kinds of applications by providing a familiar on-line environment to use existing simulation programs. EDISON (EDucation-research Integration through Simulation On the Net) project supports web simulation service with advanced research/development contents. These advanced education-research simulation programs and contents are utilized to improve the natural sciences and engineering students' research ability and adoptability for the advanced technology e-AIRS (e-Science Aerospace Integrated Research System), the trial service of EDISON_CFD, is employed to support CFD lectures 2011. In this paper, to support stable system, we present e-AIRS performance improvement such as resource reorganization, job assignment control, stable simulation list loading, and waiting time. To show the improvement effect, we describe before and after of e-AIRS performance and users’ feedback between 1st and 2nd semester 2011.

소각로 내 공기 주입은 연소가스의 체류시간, 미연분 제거 및 출구가스 온도 제어 등의 많은 영향을 끼친다. 이에 따라 2차 연소용 공기량을 변화시켜 충분한 체류시간을 확보하고 $850^{\circ}C$ 이상의 출구가스 온도를 유지하며, 높은 turbulent를 관리함으로써 안정적인 소각로 운영이 되어야만 한다. 본 연구에서는 현재 운영 중인 소각장의 소각로를 설계하고, 평균 일일 소각량을 바탕으로 1차 공기량을 산정한 후 2차 공기량을 변화하여 CFD 프로그램(Fluent)을 통해 이론적인 공기유동을 규명하였다. 또한 산정된 공기량을 바탕으로 실제 운영 중인 소각장에 적용함으로써 최적의 연소조건을 도출하였다. CFD simulation 결과 1.2차 공기비는 75:25가 최적의 결과로 나타났으며, 2차 공기 분사노즐 전 후면 유속 비는 1:3에서 가장 우수한 결과로 나타났다. 또한, 실제 운영 중인 소각로에 적용한 결과 적절한 소각로 출구온도는 질소산화물 제거 효율 및 일산화탄소 발생농도에 영향을 미치는 것으로 나타났다.

The feed air to MSW incinerator influences on the residence time of combustion gas, removal of unburnt ash and exiting gas temperature. Thus the secondary air volume could present sufficient residence time which can maintain the exiting temperature over $850^{\circ}C$. The secondary air also relates directly with the turbulence in the inside of combustion chamber, which finally provide the stable combustion condition. The present study designed a modern incinerator for a field scale, and evaluation of the potential amount of primary air based on the daily combustible quantity. From the evaluated primary air volume, the secondary air flow rate could be estimated, and its dynamic behavior was verified. In addition, the obtained air volume enables to find an optimum operation condition of the combustion. As a result of the CFD simulation, the air ratio 75 : 25 between primary and secondary air amount was optimum ratio than design criteria 72 : 28. And the flow velocity ratio of front-back of secondary air jet nozzle was found excellent at 1 : 3. In addition, the result of applied to the plant, the removal efficiency of NOx and CO generation would concentration of CO.

Boiling Water Reactor (BWR) employs the Pressure Suppression Pool (PSP) as a heat sink to prevent overpressure of the reactor vessel and containment. Steam can be injected into the PSP through spargers in normal and accident conditions and through blowdown pipes in case of a loss of coolant accident (LOCA). There is a safety limit on the maximum PSP temperature at which such steam injection might cause dynamic loads on the containment structures. The performance of the pool can be affected if thermal stratification is developed when temperature of the hot layer grows rapidly while cold layer remains inactive. Simulation of pool behavior during realistic accident scenarios requires validated models that can sufficiently address the interaction between phenomena, safety systems and operational procedures. Direct modeling of steam injection into a water pool in long-term transients is computationally expensive due to the need to resolve simultaneously the smallest space and time scales of individual steam bubbles and the scales of the whole PSP. To enable PSP analysis for practical purposes, Effective Heat source and Effective Momentum source (EHS/EMS) models have been proposed that avoid the need to resolve steam-water interface. This paper aims to implement mechanistic approaches previously developed by authors for the simulation of transient thermal stratification and mixing phenomena induced by steam injection through spargers in a Nordic BWR PSP. The latest version of the EHS/EMS models using the 'Unit cell' approach has been validated against integral effect pool tests and applied to plant simulations. Several scenarios with boundary conditions corresponding to postulated accident sequences were simulated to investigate the possibility of stratification development and the effects of activation of different systems (e.g., blowdown pipes, high momentum nozzle) on the pool behavior.

The paper presents the surface-modified NACA 2412 airfoil performance with variable cavity characteristics such as size, shape and orientation, by numerically investigated with the pre-validation study. The study attempts to improve the airfoil aerodynamic performance at 30 m/s with a variable angle of attack (AOA) ranging from 0° to 20° under Reynolds number (R_e) 4.4×10⁵. Through passive surface control techniques, a boundary layer control strategy has been enhanced to improve flow performance. An intense background survey has been carried out over the modifier orientation, shape, and numbers to differentiate the sub-critical and post-critical flow regimes. The wall-bounded flows along with its governing equations are investigated using Reynolds Average Navier Strokes (RANS) solver coupled with one-equational transport Spalart Allmaras model. It was observed that the aerodynamic efficiency of cavity airfoil had been improved by enhancing maximum lift to drag ratio ((l/d) max) with delayed flow separation by keeping the flow attached beyond 0.25C even at a higher angle of attack. Detailed investigation on the cavity distribution pattern reveals that cavity depth and width are essential in degrading the early flow separation characteristics. In this study, overall general performance comparison, all the cavity airfoil models have delayed stalling compared to the original airfoil.

In this study, a computational fluid dynamics (CFD) simulation based on an Eulerian-Eulerian approach was used to evaluate the mixing performance of a mud agitator through the distribution of bulk particles. Firstly, the commercial CFD software Star-CCM+ was verified by performing numerical simulations of single-phase water mixing problems in an agitator with various turbulence models, and the simulation results were compared with an experiment. The standard model was selected as an appropriate turbulence model, and a grid convergence test was performed. Then, a simulation of the liquid-solid multi-phase mixing in an agitator was simulated with different multi-phase interaction models, and lift and drag models were selected. In the case of the lift model, the results were not significantly affected, but Syamlal and O'Brien's drag model showed more reasonable results with respect to the experiment. Finally, with the properly determined simulation conditions, a multi-phase flow simulation of a mud agitator was performed to predict the mixing time and spatial distribution of solid particles. The applicability of the CFD multi-phase simulation for the practical design of a mud agitator was confirmed.

High fidelity nuclear reactor fuel assembly simulation using CFD method is an effective way for the structure design and optimization. The validated models and user practice guidelines play critical roles in achieving reliable results in CFD simulations. In this paper, the international benchmark MATiS-H is studied carefully and the best user practice guideline is achieved for the rod bundles simulation. Then a 5 × 5 rod bundles model in the advanced pressurized water reactor (PWR) is established and the detailed three-dimensional thermal-hydraulic characteristics are investigated. The influence of spacer grids and mixing vanes on the flow and hear transfer in rod bundles is revealed. As the coolant flows through the spacer grids and mixing vanes in the rod bundles, the drastic lateral flow would be induced and the pressure drop increases significantly. In addition, the heat transfer is enhanced remarkably due to the strong mixing effects. The calculation results could provide meaningful guidelines for the design of advanced PWR fuel assembly.