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사각형 탱크 내에서의 2차원 슬로싱에 대한 전산유체 역학적 연구
곽영균,고성호,Kwack, Young-Kyun,Ko, Sung-Ho 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.8
The present study describes a numerical analysis for simulation of the sloshing of flows with free-surface which contained in a rectangular tank moving in harmonic or pitching motion. The VOF function, representing the volume fraction of a cell occupied by the fluid, is calculated for each cells, which gives the location of the free-surface filling any some fraction of cells with fluid. The time-dependent changes of free-surface height are used for visualization subject to several conditions such as fluid height, horizontal acceleration, sinusoidal motion, and viscosity. The free-surface heights were used for comparing wall-force, which is caused by sloshing of flows. Damping effects by baffles were extensively investigated for various conditions in terms of baffle shape and position.
CFD를 이용한 이중냉각핵연료의 봉단마개 측면오리피스를 통과하는 내측수로 유동에 대한 연구
곽영균(Young Kyun Kwack),신창환(Chang Hwan Shin),이치영(Chi Young Lee),박주용(Ju Yong Park),전태현(Tae Hyun Chun),인왕기(Wang Kee In) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
A bottom end plug with side orifices was developed for sufficient coolant flowing to inner channel in the case of complete entrance blockage of the inner channel. In this event, the flow rate of the inner channel should be greater than 60% of normal condition in order to avoid a damaged condition of the nuclear fuel. The flow rate and the pressure loss coefficient were obtained through simulation analysis of single rod for the end plug. According to the blockage rate of the outer channel, flow pattern and pressure loss coefficient of the side hole were investigated.
곽영균(Young Kyun Kwack),신창환(Chang Hwan Shin),박주용(Ju Yong Park),이치영(Chi Young Lee),오동석(Dong Seok Oh),전태현(Tae Hyun Chun),인왕기(Wang Kee In) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Dual-cooled nuclear fuel for a Pressurized Water Reactor(PWR) has been introduced for a significant increase in reactor power. The spacer grid was accordingly designed. We studied about hydraulic characteristics of the developed spacer grid. The pressure loss coefficient of a spacer grid is a significant factor of the grid design because it influence the hydraulic performance of the existing fuel assembly. The pressure loss is dependent on the reduction of the flow area and the flow constriction in the spacer region of the dual-cooled nuclear fuel assembly. It is also affected by the presence or absence of coning and chamfering on the spacer grid. The pressure loss coefficients of the spacer grid were compared with three types such as spacer grid with chamfering/coining, with only coining and without chamfering/coining.
확산계면모델을 이용한 2차원 초공동 유동에 대한 수치해석
곽영균(Young Kyun Kwack),고성호(Sung Ho Ko) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Numerical simulation of supercavitating flow involves many difficulties related to interfaces of shock, expansion waves and evaporation. It is difficult to model and compute correctly jump conditions across the interfaces. In this paper, numerical analysis of supercavitating flows are performed using diffuse interface model for modelling liquid-gas interfaces. The reduced five equation model based on the mixture velocity and mixture pressure is used. These diffuse interfaces relaxation effects are solved in order to match the jump conditions of equal pressure and equal normal velocities. The numerical analysis has been conducted for two-dimensional cavitator of wedge type and disk type.
고성호(Sung Ho Ko),곽영균(Young Kyun Kwack),한승렬(Seung Yeul Han),김연태(Yun Tae Kim) 한국유체기계학회 2009 유체기계 연구개발 발표회 논문집 Vol.2009 No.-
In the present study, a fully coupled FSI(Fluid-Structure Interaction) analysis has been made to predict the flutter of a three dimensional wing. The FSI computation was made by the information exchange between CFD solution and FEM solution at each time step. Converged CFD solutions were obtained and used as the initial flow fields of the FSI computation. An unstructured FEM mesh was constructed for FEM calculation. Results of the fully coupled FSI computation were compared with those of an unsteady CFD solution, which showed why the FSI computation was essential for flutter analysis.
초공동 수중비행체의 공동영역 내부에서 분사된 배기가스가 수중비행체의 항력에 미치는 영향에 대한 수치해석적 연구
유상원(Sang Won Yoo),이우근(Woo Keun Lee),김태순(Tea Soon Kim),곽영균(Young Kyun Kwack),고성호(Sung Ho Ko) 대한기계학회 2015 大韓機械學會論文集B Vol.39 No.12
초공동 수중비행체는 수중에서 시속 300 km 이상의 속력을 가진다. 초공동 수중비행체는 로켓추진을 동력으로 사용하기 때문에 초공동 수중비행체의 수치해석은 물과 수증기, 배기가스로 이루어진 다상 유동을 다루게 된다. 배기가스가 수중비행체에 미치는 영향은 초공동 수중 비행체 성능연구에 중요한 부분이다. 본 연구에서는 초공동 수중비행체 주변의 유동장에 대한 수치해석을 통하여 배기가스가 비행체의 항력에 어떠한 영향을 미치는지 알아보았다. 배기가스가 없는 경우, 수중비행체를 둘러싼 초공동으로 물이 유입되는 재유입현상에 의해 수중비행체 항력의 변화가 발생한다. 추진체가 있는 경우 배출되는 가스는 재유입현상에 의한 영향을 감소시킨다. 또한 배기가스는 마하디스크를 생성하며 그 영향을 받아 항력 변화가 발생한다. A supercavitating vehicle has a speed of more than 300 km/h in water. A numerical analysis of the flow around a supercavitating vehicle must deal with a multiphase flow consisting of the water, vapor and exhaust gas because the vehicle is powered by roket propulsion. The effect of the exhaust gas on the vehicle is an important part in the study of the performance of the supercavitating vehicle. In the present study, the effect of the exhaust gas on the drag of vehicle was investigated by conducting numerical analysis. When there is no exhaust gas, drag of vehicle is affected by re-entrant. In the case with rocket propulsion, the exhaust gas reduces the influence of re-entrant. The exhaust gas also creates Mach disk and it changes drag profile.
소듐냉각 고속로 냉각재 순환펌프의 성능에 대한 수치해석적 연구
김연태(Yeon Tae Kim),고성호(Sung Ho Ko),곽영균(Young Kyun Kwack),이용범(Yong Bum Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
A numerical study was conducted to predict the performance curve of a downscaled model of the main coolant pump for sodium-cooled fast reactor. The ANSYS CFX program was utilized to obtain flow characteristics inside the pump as well as the overall pressure rise across the pump operating onand off-design points. Computational domain was divided into several blocks to achieve high grid quality effectively and 7.5 million nodes were used totally to resolve small leakage flows as well as the flow inside the rotating impeller. The corresponding experiment was conducted to validate CFD computed results. The comparison between the CFD and experimental data shows excellent agreement in terms of mass flow rate and head rise on and near design operating points.