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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.
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.
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.
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.
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.
박경우(Kyoungwoo Park),김진배(Jin-Bae Kim),이주희(Juhee Lee) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.12
A 3-dimensional numerical investigation of a WIG effect vehicle with DUP (direct underside pressurization) is performed to predict aerodynamic characteristics and the static height stability. DUP can considerably reduce take-off speed and minimize the hump drag while the vehicle accelerates on the water to take off. The DUP of the model vehicle, Aircat, consists of a propeller in the middle of the fuselage and an air chamber under the fuselage. The air accelerated by the propeller comes into the camber through the channel in the middle of fuselage and augments lift by changing its dynamic pressure to static pressure dramatically. However, the air accelerated by a propeller produces excessive drag and reduces static height stability.
박경우(Kyoungwoo Park),이주희(Juhee Lee),안종관(Jong-Kwan Ahn),김광수(Kwang-Soo Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The purpose of this study is to predict the effect of cyclone shape on pressure loss and its efficiency. Generally, the increase of inlet velocity of gas improves the separation efficiency, while it results in increasing in the pressure losses. The standard turbulence model with isotropic assumption cannot predict the flow characteristics with Rankine vortex but the RSM(Reynolds stress model) can estimate them properly. Because of difficulty of the adoption of turbulence model, the validation of CFD model is carried out by comparing with experimental results. It is known that the influence of the contract cone at a dust corrector is significant on pressure loss and separation efficiency. This study focuses on flow characteristics according to shapes of the cone, which is made up by angle of cone. As the results of computation, the increase of cone angle increases the separation efficiency and decreases the pressure loss.
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.
박경우(Kyoungwoo Park),최동훈(Dong-Hoon Choi),이관수(Kwan-Soo Lee),김양현(Yang-Hyun Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
In this study the optimization of plate-fin type heat sink for the thermal stability is performed numerically. The<br/> optimum design variables are obtained when the temperature rise and the pressure drop are minimized simultaneously.<br/> The flow and thermal fields are predicted using the finite volume method and the optimization is carried out by using<br/> the sequential quadratic programming (SQP) method which is widely used in the constrained nonlinear optimization<br/> problem. The results show that when the temperature rise is less than 34.6 K, the optimal design variables are as<br/> follows; B1 = 2.468 mm, B2 = 1.365 mm, and t = 10.962 mm. The Pareto optimal solutions are also presented for the<br/> pressure drop and the temperature rise.