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상경계면에서의 열유속 정보를 활용하는 상변화 모델을 이용한 상변 화열전달 수치해석 연구
손종현(Jong Hyeon Son),박일석(Il Seouk Park) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
A phase-change is a phenomenon in which the phase of a material is changed through the mass and heat transfer caused by the latent heat at the phase interface. But there are various difficulties in performing numerical analysis using the discrete grid system because of sudden changes in thermodynamic properties and complex convective flows. In this study, the numerical phase-change model based on the finite volume method using the thermal information around the phase interface is developed and the phase-change heat transfer problems are numerically investigated. To validate the new phase-change model, the one-dimensional Stefan condensation, the two-dimensional infinite corner solidification and the bubble growth problems that has the exact solution are solved. The results of temperature changed, and the interface shape obtained from the present phase-change model are more consistent with the exact solution than that of the existing phase-change models.
공기기둥이 형성된 원통 용기의 내부유동 특성에 관한 수치해석 연구
손종현(Jong Hyeon Son),박일석(Il Seouk Park),손창현(Chang Hyun Sohn) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
An air core is generated during draining after rotating cylindrical tank filled with a liquid through an axisymmetrically placed circular orifice. If the air core is generated, the draining flow rate decreased and the draining time is delayed. In this study, the formation process of the air core and internal flow characteristics of a cylindrical tank is studied by numerical methods. Several methods are used in the analysis and compared with experimental results to obtain the proper scheme. Axial, radial and swirl velocity profiles on a variety of height are shown in graphs, And the internal flow structure is analyzed from the velocity profiles, the vector plot and the stream function distribution.
배수 중에 발생하는 자유표면 와류유동 억제 방법에 관한 수치해석 연구
손종현(Jong Hyeon Son),이강욱(Kang Wook Lee),김성은(Seong Eun Kim),박일석(Il Seouk Park) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
A free-surface vortex flow forms when a liquid discharges through a drain hole. And when the liquid is draining after rotating the cylindrical tank with constant speed, there is the swirl flow accompanied with the strong axial flow in the center. The shape of free-surface in the center become thread-like or spiral and is finally connected to the outlet along the axis of tank. But, the mass flow rate of liquid phase decreases because of the gas entrainment to the outlet. In the present study, we numerically studied the liquid draining process from the cylindrical tank applied the various method of vortex suppression to prevent the generation of strong vortex flow. We investigated the draining from the cylindrical tank having the drain hole which is not situated in the center and the sloped bottom. Also, the simulation of draining from the tank installed the thin disc above the drain hole is numerically conducted. These suppression methods are effective at arresting the axial and circumferential vortices and preventing the formation of the sharp dip on the free-surface.
원형 용기 및 배수구 크기와 선회유동이 공기기둥 발생에 미치는 영향에 관한 수치해석 연구
손종현(Jong Hyeon Son),박일석(Il Seouk Park) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
A dimple appears on the free surface while rotating a cylinder tank filled with liquid. The dimple starts to get deeper concentrically during draining. In the course of time, the dimple penetrates the drain port and the free surface forms a long and slender string shape in the tank; a so-called air core phenomenon occurs. The generation of the air core depends on the size of the tank and drain port. In this study, the liquid level and the time when the air core is generated for the first time are numerically investigated for the different tank and drain port diameters and initial tank’s rotation speeds. Instead of a full three-dimensional analysis, a two-dimensional axisymmetric simulation was conducted. Several non-dimensional variables based on Buckingham’s Pi theorem are created. Finally, the critical height is correlated with the other non-dimensional variables.
계단형 배수구를 가진 원통 용기에서의 배수 과정에 관한 수치해석 연구
손종현(Jong Hyeon Son),박일석(Il Seouk Park) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.12
물이 채워진 원통 용기를 회전시킨 후 배수하면 일정시간이 지난 후 공기기둥이 발생한다. 용기의 크기, 초기 회전 속도나 교반 속도, 배수구 모양 등의 배수조건에 따라 공기기둥의 발생 여부나 발생시간이 달라진다. 본 연구에서는 2 단으로 구성된 계단형 배수구를 가진 원통 용기에서 물이 배수되는 과정을 수치해석적으로 연구하였다. 하부에 위치한 배수구 1 단은 길이와 반경이 고정되어 있고, 상부에 위치한 2 단은 길이와 반경을 변화시켰다. 2 차원 격자계에 축대칭 조건을 적용하여 원통 용기 내부의 배수유동을 해석하였다. 물과 공기의 자유표면 모양을 추적하여 수위 변화를 관찰하였으며, 배수구 2 단의 형상이 공기기둥 발생시간과 내부 유동구조 변화에 미치는 영향을 확인하였다. An air-core vortex is generated during draining after stirring a rotating cylindrical tank or after filling it with water . The formation of the air-core vortex and the time of its formation are dependent on drain conditions such as the dimensions of the tank, the initial rotation or stirring speed, and the shape of the drain port. In this study, a draining process using a two-stage drain port was numerically investigated . The length and radius of the first drain stage located in the lower part of the drain port were kept constant, whereas the radius of the second drain stage was varied for simulating the draining process. The simulation was conducted by considering an axisymmetric swirling flow for all cases. The declining water level was monitored by an interface capturing method. Further, the effects of the radius of the second drain stage on the time of formation of the air-core vortex and the internal flow structure were investigated.
백동현(Baek, Dong-Hyeon),고은애(Go, Eun-Ae),신승철(Sin, Seung-Cheol),손종현(Son, Jong-Hyeon) 한국화재소방학회 2013 한국화재소방학회 학술대회 논문집 Vol.2013 No.추계
실화책임법에 의하면, 화재 발생 시 실화자는 중대한 과실이 아닌 경우 경제적요건, 화재원인 등에 따라 손해배상액의 경감을 청구할 수 있다. 손해배상액의 경감의 여부는 실화피해자의 화재복구에 영향을 끼치게 된다. 화재발생 시 실화자가 손해배상경감청구에 책임을 입증하여야한다. 그리고 실화피해자의 원활한 화재복구를 위해 실화자의 화재보험가입의 의무와 계약자의 안전한 보호 및 보험사의 책임 일부를 분산하는 제도인 재보험의 선택적 가입을 규정하고자 한다.
1차원 Stefan 증발 문제에 대한 상변화 수치 모형 비교
김대곤(Dae Gon Kim),손종현(Jong Hyeon Son),이종희(Jong Hee Lee),오진호(Jin Ho Oh),전철홍(Chul Hong Jeon),김현기(HyunKi Kim),남현영(Hyun Young Nam),박일석(Il Seouk Park) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
The present study illustrates three models for physical phase change, based on a volume of fluid (VOF) method, of which characteristics were compared through one-dimensional Stefan problem. Numerical details for each phase change model were introduced briefly, and dependency on numerical time step and grid was examined for different three models. The control-volume-based sharp interface model showed the best applicability and numerical robustness in terms of the choice of the time step and grid sizes.
공기기둥이 형성된 원통 용기의 내부유동 특성에 관한 수치해석 연구
박일석(Il Seouk Park),손종현(Jong Hyeon Son),손창현(Chang Hyun Sohn) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.3
액체가 차있는 원통 용기를 회전 시킨 후 바닥 중앙에 위치한 원형 배수구로 액체를 배수시키면 공기 기둥이 형성된다. 공기기둥이 발생하면, 배수 유량이 감소하고 배수 시간도 지연된다. 본 연구에서는 공기기둥 형성과 배수과정 중의 용기내부의 유동특성을 수치해석 방법으로 관찰하였다. 다양한 격자계와 시간차분방법을 적용하였고 적합한 방식을 얻기 위해 실험결과와 비교하였다. 여러 위치에서의 축방향, 반경방향, 원주방향 속도 성분들의 분포를 시간대 별로 나타내었고, 속도 벡터와 유선 분포 도시를 통하여 내부 유동 구조를 분석하였다. An air core is generated during draining through an axisymmetrically placed circular orifice after rotating a cylindrical tank filled with a liquid. If an air core is generated, the draining flow rate decreases and the draining time increases. In this study, the process of the formation of the air core and internal flow characteristics in a cylindrical tank are studied by numerical methods. Several methods are used in the analysis, and the results are compared with experimental results to obtain the appropriate scheme. Axial, radial, and swirl velocity profiles on a variety of heights are shown graphically, and the internal flow structure is analyzed from the velocity profiles, the vector plot, and the stream function distribution.