Effect of Propeller-propulsion on Aerodynamic Characteristics of WIG-Craft

박경우(Kyoungwoo Park),이주희(Juhee Lee),홍철호(Chol-Ho Hong),강기준(Kijun Kang),안종관(Jong-Kwan Ahn) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

Numerical investigations for the 3-dimensional WIG effect vehicle with DUP (direct underside pressurization) have been performed to analyze aerodynamic characteristics and static height stability. The computational model is consisted of all compartments of a WIG effect vehicle such as propeller, fuselage, air chamber, main wing, and tail. Increased pressure under the fuselage by DUP-device( propeller and air chamber) can considerably reduce the take-off speed and thus minimize the effect of the hump drag which is one of the technical difficulties of the WIG effect vehicle, while the vehicle can be accelerated to take off on water. The accelerated air by the propeller comes into the air chamber through the channel at the middle of the fuselage and it results in an augmentation of the lift by changing its dynamic pressure to static one. Additionally, the DUP-device is not favorable for both stability and aerodynamic performance of the WIG effect vehicle because the accelerated air produces an excessive drag, negative pitching moment and 3-dimensional effects (that is, yawing and rolling moments). The result shows that the effect of yawing and rolling moments is not serious.

원통형 축열탱크의 디퓨저 형상이 열성층 유지에 미치는 영향에 관한 수치해석적 연구

박경우(Kyoungwoo Park) 호서대학교 공업기술연구소 2020 공업기술연구 논문집 Vol.39 No.2

축열탱크는 고온의 유입수(water)와 상대적으로 저온 상태인 저장수가 탱크내에서 혼합될 때 부력효과를 이용하여 혼합효과를 적절히 감소시킴으로서 온도의 성층화(thermal stratification)를 유지함으로 열에너지를 저장하는 장치이다. 이러한 열성층은 유입 및 저장수와의 온도차이에 의한 부력효과 뿐만 아니라 유입되는 유량, 축열탱크의 크기 및 형상, 유/출입구의 위치 등에 영향을 받으며, 혼합에 의한 열성층 파괴 방지를 위해 유입/유출부에 디퓨저를 설치할 수 있다. 이 연구에서는 원통형 축열탱크 내부에 설치된 디퓨저의 직경 및 슬롯거리 등이 열성층도에 미치는 영향을 수치적으로 규명하고자 하였으며, 이를 위하여 3차원, 비정상, 난류유동에 대한 혼합대류 열전달현상을 STAR-CCM+을 사용하여 수치적으로 해석하였다. Thermal storage tank(TST) can store a thermal energy by maintaining the thermal stratification which occurs when two types of water with different temperatures come into contact. That is, a thermal stratification arises due to the temperature variation which gives rise to a density variation in the water. Additionaly the cold and hot water are separated by means of gravitational effect. The performance of storage tanks depends on various factors such as inlet flow rates, size and shape of TST, locations of inlet and outlet in addition to the buoyancy effect. Among them, the installation of diffuser in a TST is one of the general technologies in improving the performance of TST. In the present work, the heat transfer charcteristics for three-dimensional, unsteady turbulent mixed convection are investigated numerically by using a general purpose S/W of STAR-CCM+.

노광장비 내 유동특성 규명을 통한 입자제어

박경우(Kyoungwoo Park),박차식(Cha-Sik Park),심성태(Sung-Tae Sim) 대한설비공학회 2011 대한설비공학회 학술발표대회논문집 Vol.2011 No.7

An exposure process, which is making a pattern at photoresist, is one of the key technologies in the field of semiconductor chip production. Therefore, researches on performance improvement of an exposure apparatus have been carried out recently. In this paper, CFD was used to predict the flow characteristics numerically in exposure apparatus in order to suggest the new shape for performance improvement. For them, analyses were performed for seven different shapes of exposure apparatus and parametric studies were carried out to suggest the efficient flow scheme that can reduce the vortex. As the results of this study, vortex is generally formed in the stage that is occurred an exposure at granite surface plate gap. Consequently, it is also found the modified shape which can reduce the strength of vortex in the stage. Henceforth, the authors will compare with real data of exposure apparatus in recent days.

순차적 2 차 반응표면법을 이용한 열교환기 최적설계

박경우(Kyoungwoo Park),최동훈(Dong-Hoon Choi),이관수(Kwan-Soo Lee),김양현(Yang-Hyun Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11

In this study, the shape of plate-fin type heat sink is numerically optimized to acquire the minimum pressure drop under the required temperature rise. To do this, a new sequential approximate optimization (SAO) is proposed and it is integrated with the computational fluid dynamics (CFD). In thermal/fluid systems for constrained nonlinear optimization problems, three fundamental difficulties such as high cost for function evaluations (i.e., pressure drop and thermal resistance), the absence of design sensitivity information, and the occurrence of numerical noise are confronted. To overcome these problems, the progressive quadratic response surface method (PQRSM), which is one of the sequential approximate optimization algorithms, is proposed and the heat sink is optimize by means of the PQRSM.

열시스템 최적설계에의 크리깅 방법 적용

박경우(Kyoungwoo Park),한지원(Ji-Won Han),오박균(Park-Kyoun Oh) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

The shape optimal design of the plate-fin type heat sink with vortex generator is performed to minimize the pressure loss subjected to the desired maximum temperature numerically. Evaluation of the performance function, in general, is required much computational cost in fluid/thermal systems. Thus, global approximate optimization techniques have been introduced into the optimization of fluid/thermal systems. In this study, Kriging method is used to obtain the optimal solutions associated with the computational fluid dynamics (CFD). The results show that when the temperature rise is less than 40 K, the optimal design variables are B₁= 2.44 ㎜, B₂ = 2.09 ㎜, and t = 7.58 ㎜. Kriging method can dramatically reduce computational time by 1/6 times compared to SQP method so that the efficiency of Kriging method can be validated.

와류발생기가 부착된 열교환기 최적설계

박경우(Kyoungwoo Park),최동훈(Dong-Hoon Choi) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

In this study the optimization of plate-fin type heat sink with vortex generator for thermal stability is conducted numerically. To acquire the optimal design variables, the CFD and mathematical optimization are integrated. The flow and thermal fields are predicted using the finite volume method. The optimization is carried out by means of the sequential quadratic programming (SQP) method. The results show that when the temperature rise is less than 40 K, the optimal design variables are as follows; B₁ = 2.584 ㎜, B₂ = 1.741 ㎜, and t = 7.914 ㎜. Comparing with the initial design, the temperature rise is reduced by 4.2 K, while the pressure drop is increased by 9.43 ㎩. The pareto optimal solutions are also presented between the pressure drop and the temperature rise.

실리카 에어로겔/고분자 복합재의 물리적 특성에 관한 연구

박경우(Kyoungwoo Park),이연(Yeon Lee),윤종국(Jong-Kuk Yoon),구경완(Kyung-Wan Koo) 대한전기학회 2013 전기학회논문지 Vol.62 No.9

Thermal insulation material was prepared by cross-linking chemical reaction of silica aerogel and epoxy resin, which has a high porous and vacant properties. The structural, mechanical, and thermal properties were analyzed in order to verify its application for industrial and electrical applications. The thermal conductivities were changed from 115 mW/mK to 75 mW/mK by reducing the contents of nano-porous silica areogel powders. The compressive loading is also decreased by increasing the contents of silica aerogels by 20 wt% in aerogel/epoxy composites. It is concluded that the formulated composite materials can be applied to building materials, electronics parts, and heavy industries.

헤드박스의 수송특성 및 형상최적화

박경우(Kyoungwoo Park),임효재,김병삼(Byeong-Sam Kim),이주희(Juhee Lee),김광수(Kwang-Soo Kim),박상린(Sang-Lin Park) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

A main function of paper machine headbox is to deliver a uniform dispersion of fibers in water through the manifold to a paper machine wire. The paper quality is mainly influenced by the flow characteristics taking place in a headbox. In the present work, the prediction of transport phenomena and the optimization of shape of headbox are carried out by integration of CFD and optimization technology. The back-wall of headbox is parameterized by a Bezier curve and its 9-control points and the diffuser diameters are adopted as the design variables. Because the optimal solutions can be obtained when the deviation of flow rate at each manifold and the pressure drop in the headbox are minimized, they are considered as the objective functions. To obtain the non-dominated optima, Pareto set, the multi-objective genetic algorithm is used. After twenty-five evolutions, the 6 numbers of non-dominated optima can be obtained.

화학증착 챔버 형상이 성능에 미치는 영향

박경우(Kyoungwoo Park),권정태(Jeong-Tae Kwon),박상린(Sangrin Park),한재현(Jae-Hyun Han),이헌(Heon Lee),김광수(Kwang-Soo Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

PECVD process has taken advantages of a fast process of manufacture and low cost of production because it is operated at lower temperature than that of existing process. In CVD process, the wafer quality is mainly dependent on the uniformity of film thickness and the film density may reduce due to a low temperature process. In the present work, numerical analyses are carried out to improve the deposition performance of annealing chamber. To do this, governing equations are solved by CFD and TDMAS ([(CH3)2N]3SiH) is considered as the working fluid. In addition, the effect of inlet velocity of O2 and position and length of nozzle on the deposition rate and uniformity are investigated numerically and the computational results are compared with those of experiments.

Paper Machine 헤드박스의 형상 최적설계

박경우(Kyoungwoo Park),임효재(Hyo Jae Lim),권정태(Jeong Tae Kwon),이주희(Juhee Lee),유근열(Keun Yeol Yu) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

An optimal shape for a paper machine headbox can improve the paper quality and increase the production speed, simultaneously. In the present work, the optimization of headbox shape is carried out by integration CFD and optimization algorithm. The shape of the baseline headbox is parameterized and rebuilt with four-Bezier curves. Each Bezier curve is composed of five control points. The range of design variables and their resolutions are two primary keys for the successful optimization. In the paper machine headbox, the optimum values of the design variables can be achieved when the deviation of flow rate at each tube and the amount of return flow at exit are minimized, simultaneously. To complete the optimization, the finite volume method for calculating the objective functions and a multi-objective genetic algorithm for carrying the optimization process are used, respectively. After twenty-five evolutions, the non-dominated Pareto individuals can be obtained.