• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2002년도 학술대회지
• /
• pp.307-310
• /
• 2002

A two-dimensional numerical method for inviscid two-fluid flows with evolution of density interface is developed, and an initially stationary two-dimensional fluid sheet surrounded by another fluid is studied. The Interface between two fluids is modeled as a vertex sheet, and the flow field u÷th the evolution of interface is solved by using vortex-in-cell/front-tracking method. The edge of the sheet Is pulled back into the sheet due to surface tension and a blob is formed at the edge. This blob and fluid sheet are connected by a thin neck. In the inviscid limit, such process of the blob and neck formation is examined in detail and their kinematic characteristics are summarized with dimensionless parameters. The edge recedes at $V=1.06({\sigma}/{\rho}h)^{0.5}$ and the capillary wave Propagating into the fluid sheet must be considered for bettor understanding of the edge receding.

• 한국해양환경ㆍ에너지학회지
• /
• 제10권2호
• /
• pp.107-111
• /
• 2007

경계를 가지는 비점성 2유체 유동을 해석할 수 있는 수치해법을 개발하고 이를 이용하여 초기에 정지되어 있는 액체판의 끝단에서 일어나는 수축현상을 분석하였다. 경계면은 보오텍스 쉬트로 모델하였고 유동장은 와도격자법과 경계면추적법을 적용하여 계산하였다. 액체판의 끝단은 표면장력에 의해 수축되고 뭉툭한 형상을 취하게 되고, 이러한 끝단은 잘룩한 형상의 통로에 의하여 액체판에 연결되어 안쪽으로 끌려들게 된다. 이러한 현상을 비점성 조건에서 운동에너지 변화를 포함한 무차원 수의 함수로 분석하였다. 끝단의 수축속도는 로 파악되었고 표면장력파의 전파특성이 엄밀하게 조사되어야 함을 밝혔다.

• 한국컴퓨터그래픽스학회논문지
• /
• 제25권1호
• /
• pp.13-22
• /
• 2019

본 논문에서는 입자 기반 유체 시뮬레이션에서 과하게 보존되는 액체 시트를 제거함으로써 유체 표면의 디테일을 개선시키는 새로운 방법을 제안한다. 지금까지 울퉁불퉁하고 구멍이 생기는 유체 표면의 고질적인 문제를 해결하기 위한 다양한 비등방성 접근법들은 제안되었지만, 액체 시트의 보존과 분해를 안정적으로 표현할 수 있는 방법은 제시되지 않았다. 본 연구에서는 비등방성 커널과 밀도를 기반으로 하여 물 입자를 동적으로 추가/삭제함으로 입자 기반 유체시뮬레이션에서 액체 시트의 보존과 분해라는 두 가지 특징을 동시에 표현할 수 있는 새로운 프레임워크를 제안한다. 이 방법은 입자 기반 유체 시뮬레이션 접근법에서 과하게 보존되는 액체 시트를 제거함으로써 분열되는 유체 시트의 특징을 잘 표현했으며, 결과적으로 노이즈를 없애 액체 시트의 품질을 개선시켰다.

• 소성∙가공
• /
• 제26권1호
• /
• pp.5-10
• /
• 2017

Fluid cooling is one of the manufacturing processes used to control mechanical properties, and is recently used for hot stamping of automobile parts. The formed part at room temperature is heated and then cooled rapidly using various fluids in order to obtain better mechanical properties. The formed part may undergo excessive thermal deformation during rapid cooling. In order to predict the thermal deformation during fluid cooling, a coupled simulation of different fields is needed. In this study, cooling simulation of boron steel square sheet was performed. Material properties for the simulation were calculated from JMatPro, and three convection heat transfer coefficients such as water, oil and air were obtained from the experiments. It was found that the thermal deformation increased when the difference of cooling rate of sheet face increased, and the thermal deformation increased when the thickness of sheet decreased.

• 펄프종이기술
• /
• 제31권3호
• /
• pp.35-46
• /
• 1999

Mathematical modeling provided a systematic analysis for the dynamic behavior of stock fluid in a paper machine pressurized headbox. Dynamic responses of liquid level, sheet basis weight and hydraulic pressure were predicted from the simulation model which represents the system. A unit step and asinusoidal wave load were considered as the input forcing functions in the headbox. Results are summarized as follows : 1. The dependence of sheet basis weight on liquid level in the pressurized-headbox was non -linear. 2. Liquid level in the head-box showed first-order lag with a unit step forcing to fluid input rate ; 3 . The amplitude of wave response of liquid level was inversely proportional to the time content for the sinusoidal input changes ; 4.Sheet basis weight showed second-order oscillating underamped responses for the step input load of flow rate ; 5. The damping factor in the second-order system was a function of air-pressure in the headbox ; and, 6. Dead-time existed in the measuring process for the headbox slice pressure.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
• /
• pp.1675-1677
• /
• 2005

In case of attaching thermoelectric module and heat source, the polymer sheet is attached on the $AL_{2}O_3$ plate, which Is cold and hot side of thermoelectric module, in order to enhance mechanical safty of the system. It is impossible to calculate the exact distribution of temperature and flow pattern of inner gap of thermoelectric module. Therefore CFD(Computational Fluid Dynamics) analysis was executed to determine the thermo-fluid phenomena and distribution by Fluent. As the result of these analysis, heat transfer was dominated by conduction and the difference of temperature was linear distribution according to the thickness of polymer sheet.

• 소성∙가공
• /
• 제20권5호
• /
• pp.377-386
• /
• 2011

During stamping processes, the air trapped between sheet metal and the die cavity can be highly compressed and ultimately reduce the shape accuracy of formed panels. To prevent this problem, vent holes and passages are sometimes drilled into the based on expert experience and know-how. CAE can be also used for analyzing the air behavior in die cavity during stamping process, incorporating both elasto-plastic behavior of sheet metal and the fluid dynamic behavior of air. This study presents sheet metal forming simulation combined simultaneously with simulation of air behavior in the die cavity. There are three approaches in modeling of air behavior. One is a simple assumption of the bulk modulus having a constant pressure depending on volume change. The next is the use of the ideal gas law having uniform pressure and temperature in air domain. The third is FPM (Finite point method) having non-uniform pressure in air domain. This approach enables direct coupling of mechanical behavior of solid sheet metal and the fluid behavior of air in sheet metal forming simulation, and its result provides the first-hand idea for the location, size and number of the vent holes. In this study, commercial software, PAM-$STAMP^{TM}$ and PAM-$SAFE^{TM}$, were used.

• 유공압시스템학회논문집
• /
• 제5권2호
• /
• pp.8-13
• /
• 2008

Shell-and-tube type heat exchangers are generally classified with fixed tube-sheet and floating tube-sheet heat exchangers. In this paper, we employed the fixed tube-sheet heat exchangers. We theoretically investigated the safety evaluation of our shell-tube heat exchanger by axial, bending and equivalent stress of fin tubes, tube plates, channels and shell. Design pressure ranges were chosen pressure($0.6{\sim}2\;MPa$) on tube side and 200 %(3 MPa) of Maximum pressure on shell side for safety evaluation of heat exchangers. This research will be useful for fabrication of heat exchangers to prevent against damage hazard of heat exchangers in operation.

• Journal of Magnetics
• /
• 제21권3호
• /
• pp.468-475
• /
• 2016

In this article, entropy generation on MHD Williamson nanofluid over a porous shrinking sheet has been analyzed. Nonlinear thermal radiation and chemical reaction effects are also taken into account with the help of energy and concentration equation. The fluid is electrically conducting by an external applied magnetic field while the induced magnetic field is assumed to be negligible due to small magnetic Reynolds number. The governing equations are first converted into the dimensionless expression with the help of similarity transformation variables. The solution of the highly nonlinear coupled ordinary differential equation has been obtained with the combination of Successive linearization method (SLM) and Chebyshev spectral collocation method. Influence of all the emerging parameters on entropy profile, temperature profile and concentration profile are plotted and discussed. Nusselt number and Sherwood number are also computed and analyzed. It is observed that entropy profile increases for all the physical parameters. Moreover, it is found that when the fluid depicts non-Newtonian (Williamson fluid) behavior then it causes reduction in the velocity of fluid, however, non-Newtonian behavior enhances the temperature and nanoparticle concentration profile.

• 대한기계학회논문집
• /
• 제16권5호
• /
• pp.873-882
• /
• 1992

본 연구에서는 축대칭 형상의 하이드로 미케니칼 디프드로잉 공정을 강소성 유한요소법으로 해석하는 것이다. 본 논문에서는 Fig.1에서 보이는 바와 같은 경우 에 대하여 평두 펀치(flat headed punch)를 사용한 공정을 강소성 유한요소법으로 해 석하였으며 펀치 행정에 따른 챔버내의 압력 및 플랜지부의 압력분포를 구하였다. 접촉부의 처리는 플랜지부의 압력분포를 구하였다. 접촉부의 처리는 Yang등이 제안 한 방법을 적용하였다. 이론해석의 타당성을 알아보기 위하여 금형을 설계, 제작하 고 실험을 수행하여 결과를 비교 검토하였다.