A cyclone separator is a device that separates solid particles from a fluid using centrifugal force and gravity in its inner chamber. Among cyclone separators, the separator that uses water as a working fluid is called as hydrocyclone separator, which has been developed for the purpose of dehydrating solid mixtures with a proportion of solids floating in liquids greater than 1, such as soil, coal, and cement slurry. In this paper, a hydrocyclone was designed based on the previously proposed design method, and how different the performance is from the targeted value was investigated using the computational fluid dynamics.

The importance of urban green space creation is increasingly recognized as the most realistic and efficient approach for fine dust mitigation in urban areas. Particularly considering the characteristics of domestic cities, the application of buffer green spaces along roads can maximize the efficiency of fine dust reduction without the need for separate green space creation. Accordingly, this study analyzed the fine dust mitigation effects based on the types of plantings in the central dividers and roadside trees in Jeonju City, Jeollabuk-do. To do this, we controlled various external variables of urban space and considered the planting arrangement types in the central dividers, carrying out the analysis using a CFD simulation. The simulation results confirmed that the central dividers with plantings demonstrated more effective ultrafine dust reduction than those without. Moreover, the arrangement of roadside trees showed a greater ultrafine dust reduction effect when adopting a multilayered structure compared to a single layer. Based on these findings, we concluded that installing both trees and shrubs simultaneously in the central dividers and along roads was effective for ultrafine dust mitigation. On this basis, we quantified the dust reduction effects of plants in urban street environments and proposed planting guidelines for roadside green spaces to improve air quality.

Failure to comply with the performance test requirements for the centrifugal pumps at power plants often results in performance dissatisfaction as a result of field tests. This study proposed a method of reducing the uncertainty of the field test results by evaluating the systematic error in the measurement system caused by failure to follow the test requirements using the computational fluid dynamics(CFD) technique. As a result of the evaluation of the systematic error and reflecting it in the performance test data, it was confirmed that the error occurred at a constant rate with respect to the flowrate and that the pump, which showed a difference in performance actually had the same performance.

In order to analyze the pressure drop of the fluid passing through the hydraulic coupler, a flow model using the Computational Fluid Dynamics (CFD) analysis technique was developed and the fluid flow rate and pressure distribution inside the coupler were analyzed. The analysis model was corrected by comparing the pressure drop measurement using a 6.35mm hydraulic coupler with the ISO reference value and the simulation prediction value. Using the calibrated model, the flow rate and pressure drop of 13 types of hydraulic couplers distributed on the market were analyzed, and their performance was determined by comparing them with ISO reference values. In the case of type A coupler, the pressure drop was generally higher than the ISO reference value, and in the case of type B coupler, the pressure drop was similar to or lower than the ISO reference value. It was confirmed that the complex flow analysis inside the hydraulic coupler could be easily performed through computational fluid dynamics (CFD) modeling, and based on this, problems could be identified and performance could be improved performance.

국내 자연재난 피해의 50%는 태풍에 의해 발생하며, 최근 태풍에 동반된 강풍에 의한 인명 피해가 빈번하게 발생하고 있다. 재난 피해 저감을 위한 재난 안전 교육의 일환으로 국내의 강풍체험시설은 대부분 제한된 공간에 설치되어 체험을 위한 내부 유동장의 효과적 설계가 필요하다. 이를 위해 본 연구에서는 전산유체역학 기법을 이용하여 강풍 체험장의 내부 유동장을 해석하였으며, 내부 구조 형상으로 인해 발생하는 압력 저항을 공간 저항으로 정의하였다. 기존 강풍 체험장에 대한 분석 결과 기존의 수평 방향 풍로 구조로 인해 매우 불균질한 내부 유동장이 형성되고 큰 공간 저항이 발생함을 확인하였다. 이를 개선하기 위하여 풍로를 수직 방향으 로 변경함으로써 공간 저항을 80% 가까이 감소시킬 수 있음을 확인하였으며, 체험장 내부 유동장의 균질도도 크게 향상되어 실질적 강풍 체험장 구현이 가능함을 확인하였다.

The objectives of this study were to develop the optimal structures of recirculating aquaculture tank for improving the removal efficiency of solid materials and maintaining water quality conditions. Flow analysis was performed using the CFD (computational fluid dynamics) method to understand the hydrodynamic characteristics of the circular tank according to the angle of inclination in the tank bottom (0°, 1.5° and 3°), circulating water inflow method (underwater, horizontal nozzle, vertical nozzle and combination nozzle) and the number of inlets. As the angle in tank bottom increased, the vortex inside the tank decreased, resulting in a constant flow. In the case of the vertical nozzle type, the eddy flow in the tank was greatly improved. The vertical nozzle type showed excellent flow such as constant flow velocity distribution and uniform streamline. The combination nozzle type also showed an internal spiral flow, but the vortex reduction effect was less than the vertical nozzle type. As the number of inlets in the tank increased, problems such as speed reduction were compensated, resulting in uniform fluid flow.

본 논문은 하수관 보강 방법 중 보강튜브경화공법(CIPP)의 종점부 미경화 문제를 해결하기 위해 설계된 증기이송튜브 시스템에 대한 유동해석 결과를 보고한다. 설계된 증기이송튜브의 유동해석을 위해 SolidWorks Flow Simulation을 이용하여 해석을 수행하였다. 100mm, 150mm, 200mm의 직경을 갖는 증기이송튜브에 대한 유동 흐름 및 온도 분포가 유동을 해석을 통해 검토되었다. 해석 결과를 통해 증기이송튜브의 직경이 증가함에 따라 경화온도를 만족하는 CIPP 내부 길이가 증가하는 것이 확인되었다. 또한, 직경 200mm를 제외한 모든 직경의 증기이송튜브의 입구에서 증기 역류 현상이 나타남을 확인하였다. 이에 증기이송튜브의 최적 직경은 200mm로 결정되었으며, 이에 대한 유동해석을 통해 증기주입을 시작하고 350초 경과 이후에 CIPP 내 모든 길이에서 경화온도를 만족하는 것을 확인하였다.

본 논문에서는 상용코드인 ANSYS CFX를 통한 해양레저 스포츠 및 야외 활동 시 사용 가능한 휴대용 수평축 수차의 유입유속(U) 및 주속비(TSR, Tip Speed Ratio) 변화에 따른 성능해석을 수행하였으며, 해석결과 및 유동장 분석을 통해 설계에 대한 검토 및 장치의 성능을 확인하였다. 또한, 추가적으로 블레이드의 피치각도(αpitch) 변화에 따른 성능해석을 통해 수차의 성능개선에 필요한 데이터를 획득하고자 하였다. 본 논문의 연구 결과 수치해석 케이스 중 주속비 4인 경우, 모든 유입속도 및 블레이드 피치 각도에서 가장 높은 성능을 보였으며, 설계 유속 이하의 일부 조건에서도 설계 출력인 30 W 이상의 출력을 보였다. 그리고 수치해석 케이스 중 가장 높은 출력과 출력계수는 유입유속 1.5 m/s, 블레이드 피치 각도 3°, 주속비 4에서 보였으며, 출력 약 85 W, 출력계수 약 0.30이었다.

This study aims to observe the wind load characteristics around two-dimensional rotor blade of small wind turbine under high wind speed. The CFD analysis on the blade shape of NACA-4418 is performed to understand the wind load(i.e., drag and lift coefficient). In the results, the drag and lift coefficient were estimated to be 0.013, 0.44, respectively, at the wind speed 35m/s(wind speed at the height of wind tower, z=70m) and angle of attack 3°. By using the lift, drag coefficient and the appropriate assumption of the blade length, the number of blade and the tip speed ratio(TSR), the proper blade shape was obtained. On the base of this basic study, various conditions for Reynolds number and aerodynamic analysis including angle of attack according to parametric test need to study more in the future. Also assessment for the blade need to study safety on wind pressure coefficient and distribution according to wind characteristics.

Abalone (Haliotis discus hannai) is a shellfish that feeds on kelp and, as a product, it can often achieve a high market value. However, the dissolved oxygen (DO) levels in coastal waters in Korea have been negatively impacted by pollution from many anthropogenic sources. Herein, a computational fluid dynamics (CFD) software package was used to analyze the distribution of the DO concentration within an abalone containment structure. A finite volume approach was used to solve the Reynolds-averaged Navier–Stokes equations combined with a k–ε turbulence model to describe the flow. The distribution of DO was determined within the control volume domain, and the transport equations of the pollutants were interpreted using a CFD model. The CFD analysis revealed that more than 60% and 30% of the relative oxygen concentration in one and two containers, respectively, was maintained when the flow acts along the six sheets of polyethylene plates. Therefore, it is clear that the abalone plate shelters should be placed parallel to the flow.

With global warming and the rapid increase in urbanization accompanied by a concentration of population, the urban heat island effects (UHI) have become an important environmental issue. In this study, rooftop greening and permeable asphalt pavement were selected as measures to reduce urban heat island and applied to a simple virtual urban environment to simulate temperature change using ENVI-met. A total of five measures were tested by dividing the partial and whole area application of each measure. The results showed that the temperature range of the base experiment is 33.11-37.11 ℃, with the UTCI comfort level described as strong heat and very strong heat stress. A case applied permeable asphalt has a greater temperature difference than a rooftop greening case, the larger the area where each condition was applied, the greater the temperature change was.