In this study used Computational Fluid Dynamic analysis to examine NOx reduction in hydrogen combustion, analyzing six conditions with varying air/fuel ratios, temperatures, and concentrations. Results were compared between two combustor shapes and previous experimental data. Findings showed increased air/fuel ratios decreased flame temperature and increased post-combustion O2. NOx emissions peaked at high temperatures and low O2. Numerical results aligned with previous experimental trends, validating the approach. Combustor shape differences, reflecting variations in fuel and air pipes, significantly affected flow rates and combustion positions. This reduced NOx emissions up to a certain air/fuel ratio, but excessive increases diminished this effect. The study highlights the complex relationship between combustor design, operating conditions, and NOx emissions. Further research is needed to optimize NOx reduction by considering pipe numbers and combustion locations. Future studies should explore various combustor geometries, fine-tune air/fuel ratios, and investigate additional parameters influencing NOx formation and reduction in hydrogen combustion systems.

본 논문에서는 다중 연결 NURBS 패치 모델에 대한 등기하해석방법을 제시하고 이를 기하학적으로 엄밀한 쉘의 해석에 적용하였 다. 서로 다른 NURBS 패치를 연결할 떼 조정점 망(control point meshes)의 밀도와 패치간의 불연속성으로 인해 등기하해석이 부정확 해질 수 있다. 이러한 문제를 해결하기 위해 니셰(Nitsche) 방법을 등기하해석법에 적용하여 두 패치 사이의 변위와 견인력(traction) 의 정합성(compatibility)을 확보하였고, 최종 유도된 해석 방정식이 대칭성을 유지하도록 하였다. 추가되는 경계 조건은 패치간 경계 의 적분으로 표현되기 때문에 계산비용이 크게 증가되지 않는다. 시스템 방정식이 양정 행렬(positive definite matrix)이 되도록 안정 성 매개변수(stability parameters)를 도입하였으며 일반화된 고유치 해석을 통해 두 패치사이의 조정점 밀도에 따른 안정성 매개변수 의 값과 응력장의 해의 정확성을 분석하였다. 이 다중 패치 등기하해석법을 1차 전단변형을 고려한 기하학적으로 엄밀한 쉘요소의 해석에 적용하였으며, 니셰 방법을 사용함으로써 패치간의 변위 및 응력 연속성이 향상된 결과를 확인 할 수 있었다.

본 논문에서는 다중 연결 NURBS 패치 모델에 대한 등기하해석방법을 제시하고 이를 기하학적으로 엄밀한 쉘의 해석에 적용하였 다. 서로 다른 NURBS 패치를 연결할 떼 조정점 망(control point meshes)의 밀도와 패치간의 불연속성으로 인해 등기하해석이 부정확 해질 수 있다. 이러한 문제를 해결하기 위해 니셰(Nitsche) 방법을 등기하해석법에 적용하여 두 패치 사이의 변위와 견인력(traction) 의 정합성(compatibility)을 확보하였고, 최종 유도된 해석 방정식이 대칭성을 유지하도록 하였다. 추가되는 경계 조건은 패치간 경계 의 적분으로 표현되기 때문에 계산비용이 크게 증가되지 않는다. 시스템 방정식이 양정 행렬(positive definite matrix)이 되도록 안정 성 매개변수(stability parameters)를 도입하였으며 일반화된 고유치 해석을 통해 두 패치사이의 조정점 밀도에 따른 안정성 매개변수 의 값과 응력장의 해의 정확성을 분석하였다. 이 다중 패치 등기하해석법을 1차 전단변형을 고려한 기하학적으로 엄밀한 쉘요소의 해석에 적용하였으며, 니셰 방법을 사용함으로써 패치간의 변위 및 응력 연속성이 향상된 결과를 확인 할 수 있었다.

얕은 물에서 선박과 바닥의 상호작용으로 인해, 제한이 없는 깊은 물에서 운항할 때와 비교하여 저항이 증가하는 현상이 발생 한다. 이러한 천수효과에 의해 증가하는 저항은 주로 조파저항에 기인하기 때문에, 본 연구에서는 유람선을 대상으로 LCG(Longitudinal Center of Gravity)의 위치 변경을 통해 성능을 최적화하여 조파저항을 감소시키는 것을 목표로 진행하였다. 수치해석 시뮬레이션을 통해 LCG 위치를 최적화하여 저항의 최소값을 찾고, 이후 수심의 깊이에 따른 영향을 분석하였다. 분석 결과, 37.5% - 52.5% Lpp의 영역에서의 LCG 변화는 총 저항에 큰 영향을 주었으며, 깊은 물의 조건에서는 총 저항의 최대값과 최소값을 비교하였을 때, 72.67%의 큰 차이를 보이 는 반면, 얕은 물 조건에서는 그 차이가 62.97% 정도로 비교적 낮은 차이를 보인다. 수심의 깊이에 따른 효과는 수심이 낮을수록 총 저항 이 증가하는 경향을 보였다. 깊은 물과 비교하여 1.5m의 얕은 물에서는 총 저항이 최대 67.68% 가량 증가하는 것으로 분석되었다. 이 경우 총 저항 증가의 주요 원인은 전체 저항의 84.99%를 차지하는 조파저항에 의한 것으로 판단된다.

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.

본 논문에서는 전산점근해석기법을 사용하여 복합재료 보에 대한 경계층 해를 계산하고, ANSYS 결과와 비교 검증하였다. 경계층 해는 내부해와 순수 경계층 효과의 합으로 표현되기 때문에, 내부 및 경계층에 대한 수학적으로 엄밀한 정식화를 요구한다. 전산점근 해석기법은 수학적으로 매우 강력한 기법으로, 이러한 문제에 유용하다. 그러나 경계층과 내부 해들의 연결을 시키기 쉽지 않은데, 본 연구에서는 가상일의 원리를 통해 생브낭의 원리와 내부 및 경계층 문제를 체계적으로 분리하였다. 경계층 해는 팝코비치-패들 고유 벡터를 계산하여, 실수부와 허수부 벡터들의 선형 조합으로 표현하고, 내부 해의 워핑 함수들을 보상할 수 있도록 최소오차 자승법을 적용하였다. 계산된 해들은 2차원 유한요소 해석 결과와 비교하여 정성적일 뿐만 아니라 정량적으로도 잘 일치하는 결과를 얻었다.

Hydraulic cylinders are hydraulic system parts widely used in various industries such as construction machinery, machine tools, robots, automobiles, and automation systems. The maximum capacity of vane pumps used in machine tools is 70bar, but the actual operating pressure is less than 50bar. The allowable pressure of a commercial hydraulic cylinder is 140 - 210 bar, so it is heavy and uneconomical because it uses thick and strong materials. In this paper, we intend to develop a small and lightweight hydraulic cylinder suitable for the allowable pressure of 50bar or less so that it can be used in the hydraulic system field. In order to develop a compact hydraulic cylinder, flow analysis, and structural analysis were conducted under piston forward and backward conditions. The analyzed flow rate value was calculated to be suitable for the operation of the hydraulic cylinder. As a result of comparing the stress calculated under the forward/backward condition of the piston with the yield stress of the material, the safety factor was calculated to be more than 2.5.

Microclimate analysis was conducted through actual measurement according to land use status in urban, and CFD analysis was conducted to analyze and predict the microclimate characteristics of urban, and compared and analyzed with the actual measurement results. It was measured in high-rise areas and parks, and the temperature of the park area was 0.4 to 0.6℃ lower, and the relative humidity was 1.0 to 3.0% higher. The correlation coefficient was obtained by comparing the results of the computational fluid analysis with the results of the computational fluid analysis at the actual location located within the CFD analysis area for validation. The seasonal correlation coefficients are all higher than 0.8, so it is judged that they can be applied to microclimate analysis in urban area. The computational fluid analysis was divided into three areas (low-rise, low and high-rise, and high-rise) centered on the A2 point. On average, the low-rise area was 0.1 to 0.4% higher than the high-rise area. In the low and high-rise area and high-rise area, the pith of buildings are wide, so the airflow is smooth, so it is judged that the temperature is relatively low.

In this paper, durability verification of forged wheels for automobiles were performed using the finite element method for bending fatigue analysis and impact analysis. In addition, the durability analysis environment of forged wheels was implemented. By analyzing the stress distribution on the surface of the forged wheel, the area with a high possibility of breakage was identified and improved. The durability analysis of the initial model forged wheel was performed by bending fatigue analysis and impact analysis, The stress distribution of the forged wheel surface was analyzed through the analysis results of the initial model. and the spokes, flanges, hubs, and rear parts are less likely to be damaged were cut to reduce the weight by about 10%, and the reliability of the improved model was confirmed.

Micro-climate measurements and computational fluid analysis were conducted to use it as basic data for the preservation and management of the old house of Kim Myung-kwan, a traditional building that is National Folk Cultural Property No. 26. As a result of the actual measurement, the temperature and humidity are relatively evenly distributed indoors unlike outdoors, but the temperature and humidity vary depending on the time change and the installation location in the outdoors. It was found that the temperature increases after dawn and the temperature varies depending on the installation position around 14:00–15:00, when the temperature becomes the highest. In particular, the temperature was high at the outdoor measurement point adjacent to the building and the fence. As a result of the computational fluid analysis, the temperature was high in the buildings and fences in the old house or in the area adjacent to the building, and it was about 1℃ higher than the surrounding area. In this area, it is judged that the thickening of wood will occur more severely than in other locations, and special preservation management is required.

CFD was used to study the change in the operation of the governor to check the effect of response delay due to residual air in the governor cylinder, which adjusts the pump RPM of the Turbine Driven Aux. Feed Water Pump(TD AFWP) in the Nuclear power plant. As a result of analysis, as the amount of internal air increased, the time delay also increased proportionally, and a time delay of up to 0.2 sec. occurred. As in the theory, it was confirmed that the cylinder operation delay occurred depending on the presence or absence of a compressive fluid such as air, but the time delay wat not enough to significantly affect the pump operation.

In this paper, numerical simulations were conducted to secure both flow distribution and uniform flow discharge through a wall mount type air sterilizer. In order to increase the reliability of the simulation results where there is no well-known validation case for air sterilizer, mesh sensitivity study was performed under the constraint that y+ set to one for k-w SST turbulent modeling for both the air sterilizer and the fan. The installation of various guides and structures was reviewed in the point of flow distribution and pressure drop inside the sterilizer, and the exhaust pressure conditions were predicted to secure uniform flow discharge at outlets. This study has been done based on the computational analysis during the development stage of the air sterilizer, and the results will be verified through physical testing after production of prototype.

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.

Valves are one of the indispensable components in modern industry. Filling and de-pressure connectors in rocket valves used for space launch vehicles are very important parts for smooth fluid supply. For this reason, an optimized design that can improve efficiency, miniaturization, weight reduction, and safety of the valve at the same time is required. In this work, flow analysis and structural analysis were performed through 3D modeling using computational numerical analysis for open type filling and de-pressure valves. As results, the flow velocity and pressure distribution of the fluid were analyzed through the flow analysis of valve, and stress distribution was conducted in structural analysis. Through this study, it is consequently expected to provide valves of various specifications by performing production and performance test evaluation of development prototypes.

Among the various causes of the vibration problem of the radial sluice gate used in Saemangeum, the effect of flow-induced vibration was studied by the method of computational fluid analysis. In this study, the effect on the flow-induced vibration of the Saemangeum radial sluice gate was evaluated by 2D unsteady flow numerical analysis using ANSYS Fluent. Gate opening cases of 0.2m, 0.3m, 0.4m, 0.5m, and 1.0m were analyzed. As a result, the flow-induced vibration characteristics due to the instability of turbulent flow were observed through FFT analysis. As the gate opening increases, the frequency of the maximum amplitude moves gradually to a lower frequency region with the reduction of the magnitude. Therefore the flow-induced vibration effects can be considered as small with the gate opening increase.

When operating at high speed on a vessel, a high-speed planing hull occurs nonlinear movements such as stern trim and large sprays. This phenomenon results in the hindrance of stability, embarkation and mission performance. Excessive stern trim during the slides decreases propulsion efficiency and visibility of helmsman due to porpoising and changing the attack angle of the fluid flowing into the propeller. To improve these problems, an outboard floating plate is installed on the cavitation plate to greatly suppress or eliminate the porpoising phenomenon. In this study, to analyze the performance of the floating plate mounted on the outboard engine, numerical analysis was carried out to investigate the resistance applied to the floating plate and the lift generated according to the change of the angle of attack and the flow velocity. The reliability of the floating plate mounted on the outboard engine was verified by applying the floating plate according to the speed and the angle of attack.