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RISS 인기검색어
- 검색키워드
- 주제어 : 등엔트로피과정(Isentropic Process) (검색결과 4 건)
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황세준(Sejoon Hwang),박원규(Warngyu Park),김철(Chul Kim),오세욱(Sewook Oh),조남영(Namyoung Cho) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
In sheet metal forming process using press and draw die some defect can be made because of the high pressure of air pocket between draw die and the product. The purpose of this study is to develop a program to decide an optimal combination of air vent hole size and number to prevent those defect on product. The air inside air pocket is considered as ideal gas and the compression and expansion is assumed as isentropic process. The mass flow is computed in two flow condition: unchocked and chocked condition. The present computation obtains required cross-sectional area of air vent hole for not exceeding the user specified pressure such as the pressure for yielding strength of the product or the pressure for unchocked flow. To validate the program the present results are compared with the results of other researchers and commercial CFD code.
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비압축성 자유표면 유동에서 갇힌 기체의 등엔트로피 및 등온과정에 따른 공기 완충 효과 변화
신상묵(Sangmook Shin) 한국전산유체공학회 2019 한국전산유체공학회지 Vol.24 No.3
A developed code is applied to simulate the air cushion effects caused by isentropic and isothermal processes of entrapped air in incompressible free surface flows. The code uses a pressure-based method for the unified conservation laws of incompressible and compressible fluids. To calculate a pressure field, including compressible entrapped gas region, a pressure Poisson equation is solved for the whole domain. The effects of gas compressibility are reflected in the source terms of the pressure Poisson equation. The oscillations of water column in a closed tube are simulated, which are caused by compression and expansion of air on both sides of the water column. A good agreement is achieved for comparison of computed time history of pressure at the end of the closed tube with other reported result. In the isentropic process, the period of the oscillation becomes shorter and the amplitude becomes bigger. It is shown that the variations in the period and the amplitude can be readily explained based on analogy of a spring-mass system. As the initial velocity of the water column increases, the non-linearity of pressure oscillation becomes more noticeable. However, the variations in oscillation characteristics according to the processes of air remain unchanged. The developed code is applied to compare the air cushion effects caused by isentropic and isothermal processes of entrapped air in broken dam flows. Similar tendencies are observed for variations in period and amplitude of pressure oscillations, according to the assumptions on density-pressure relationship of entrapped air in broken dam flows.
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보텍스튜브 유동의 에너지분리 및 열역학특성에 관한 수치적 연구
최훈기(H.K. Choi),유근종(G.J. Yoo),임윤승(Y.S. Lim) 한국전산유체공학회 2018 한국전산유체공학회지 Vol.23 No.2
A vortex tube is a simple energy separating device which splits a compressed air stream into a cold and hot stream without any external energy supply or chemical reactions. In this article computational fluid dynamics analysis of a 3-D steady state and turbulent flow has been carried out through a vortex tube. The present research has focused on the energy separation and thermodynamic behavior of a vortex tube have been investigated. The temperature separation occurs because of the heat transfer from the central flow to the peripheral flow. Through the interpretation of the second law of thermodynamics, the generation of entropy shows that irreversible processes occur in the vortex tube.
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황세준(Sejoon Hwang),박원규(Warngyu Park) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
While stamping process, air may be trapped between die and blank and it builds up high pressure. This induces the imperfections on the blank surface and makes extreme high tonnage of punch required to reach home position. To prevent these problems, the air ventilation holes are drilled through the die. But, most of die makers drill air ventilation holes excessively on trial and error basis. The present work has developed a simplified mathematical formulation for computing the pressure of air pocket at given cross-sectional area of air ventilation holes and the pressure of air pocket was compared to commercial CFD code and experiments. The pressure was well agreed with the result of CFD code and experiments. The present work could also calculate the optimum cross-sectional area of the air ventilation hole not to exceed the prescribed maximum pressure of air pocket by using the Bisection method.
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