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최영심(Y.S. Choi),홍준호(J.H. Hong),황호영(H.Y. Hwang) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
Cartesian grid system has mainly been used in the casting simulation even though it does not nicely represent sloped and curved surfaces. These distorted boundaries cause several problems. A special treatment is necessary to clear these problems. A cut cell method on Cartesian grids has been developed to simulate three-dimensional mold filling. Cut cells at a cast-mold interface are generated on Cartesian grids. Governing equations were computed using volume and areas of cast at cut cells. In this paper, we propose a new method that can consider the cutting cells which are cut by casting and mold based on the partial cell treatment (PCT). This method provides a better representation of geometry surface and will be used in the computation of velocities that are defined on the cell boundaries in the Cartesian gird system. Various test examples for several casting process were computed and validated. The analysis results of more accurate fluid flow pattern and less momentum loss owing to the stepped boundaries in the Cartesian grid system were confirmed. We can know the momentum energy at the cut cell is conserved by using the cut cell method. By using the cut cell method, performance of computation gets better because of reducing the whole number of meshes.
모델러와 CAE 를 활용한 최적 금형 방안 설계 기술 개발
임채호(C. H. Lim),곽시영(S. Y. Kwak),조인성(I. S. Cho),황호영(H. Y. Hwang) 한국소성·가공학회 2009 소성가공 : 한국소성가공학회지 Vol.18 No.2
In the casting industry field, a lot of researches have been carried out to maximize soundness and productivity and improve quality of mass produced products. The researches on the optimum mould design by using computer simulation have achieved a lot of accomplishments in the die-casting process especially. Their results are utilized to mass-produce sound products in their field. But there are some difficulties to use the simulation in order to make the design of product and mould. In general, repetitive calculations of computer simulation require much analyzing time in order to make sound design of them. Another difficulty is that only expertise technicians can analyze results of the simulation. In order to solve such a problem, we are building mould design optimization system which consists of knowledge-based module, simulation, optimization module and interactive modeler(it is based on the commercial modeler). By using and interacting between these modules of that system, we can easily make an optimum design of mould and construct the database. This study introduce the general process of the system and connection method between the modules is mentioned above and some examples to apply it to real product.
Yin Song,곽시영(S.Y. Kwak),황호영(H.Y. Hwang) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.3
The safety valve is an essential device for high-pressure equipment; because high-pressure equipment is used in many fields, the use of safety valves is also increasing. Safety valves are used in various fields such as the petroleum industry, power plants, and nuclear power industries. In the 19th century, many boiler explosion accidents occurred due to improper boiler design or the failure of safety valves used in boilers. These incidents drew the attention of the US government, and the American Society of Mechanical Engineers (ASME) enacted the first ASME code for safety valves in response to government requirements. A safety valve is a device used to protect high-pressure systems and people from accidents, and because of its importance, many related studies have been conducted, and related standards are continuously being updated. In actual safety valve experiments, it is difficult to observe the characteristics of fluid flow. In this study, the opening process of a safety valve under high pressure was studied using a simulation method. Analysis was conducted using the commercial software COMSOL Multiphysics and the fluid–structure interaction (FSI) technique. The FSI is calculated by reflecting the interaction between a structure and fluid and is a suitable method for analyzing the safety valve operation process. Two shapes that can reduce flow resistance were designed by analyzing the simulation results and the same flow analysis was performed on these shapes. By comparing the proposed shape’s simulation results with those of existing shapes, it was confirmed that the pressure loss was reduced in the improved method, and the flow rate was further increased due to a relatively low pressure loss. This means that the fluid inside the pressure vessel can be discharged faster and the pressure can be lowered faster, so it was determined that the improved shape safety valve showed better performance.