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An Advection Scheme for the Transport of Fractional Volume of an Incompressible Fluid
곽호상(Ho Sang Kwak),Kunio Kuwahara 한국전산유체공학회 1998 한국전산유체공학회지 Vol.3 No.1
서로 섞이지 않는 두 비압축성 유체의 유동을 해석하기 위하여 VOF방법에 기초한 수치기법을 개발하였다. 유체간의 계면형상의 거동은 유동장내의 윤체의 점유체적비의 변화에 의해 요사되는데 이를 지배하는 이동 방정식을 풀기 위한 새로운 대류항 계산법을 고안하였다. 대류항은 유체계면의 방향에 따라 풍상법과 역풍상법의 적절한 조합을 취하여 계산하는데 여기에 대각방향의 상류효과를 포함시켜 시간에 대한 2차 정확도를 갖도록 하였다. 또한 이 방법을 유량보정수송(FCT)법과 결합시켜 해의 단조성을 보장하였다. 몇 가지 단순 문제에 대한 시험 결과 이 기법이 수치오차에 의한 계면형상의 변형과 파손올 감소시킴을 확인하였다.
LCD 기판 세정건조용 스피너 설계를 위한 내부유동 해석
곽호상(Ho Sang Kwak),이상우(Sang Woo Lee),이상현(Sanghyun Lee),김용범(Yong Bum Kim) 한국전산유체공학회 2002 한국전산유체공학회 학술대회논문집 Vol.2002 No.-
A numerical model is employed for design of a spinner device to dry the 5-th generation LCD glass panel. The turbulent flow in a spinner is driven by rotation of a large disk and suction by the exhaust system connected to vacuum chamber, which is simulated by using the FLUENT package, Based on numerical simulation, the required capacity of exhaust system is assessed. The effects of the presence of cover on the flow characteristics ate examined. A computational trouble shooting is attempted to resolve the problem of panel rising which occurred in real experiments.
An Advection Scheme for the Transport of Fractional Volume of an Incompressible Fluid
곽호상(Ho Sang Kwak),Kunio Kuwahara 한국전산유체공학회 1998 한국전산유체공학회지 Vol.3 No.1
서로 섞이지 않는 두 비압축성 유체의 유동을 해석하기 위하여 VOF방법에 기초한 수치기법을 개발하였다. 유체간의 계면형상의 거동은 유동장내의 윤체의 점유체적비의 변화에 의해 요사되는데 이를 지배하는 이동 방정식을 풀기 위한 새로운 대류항 계산법을 고안하였다. 대류항은 유체계면의 방향에 따라 풍상법과 역풍상법의 적절한 조합을 취하여 계산하는데 여기에 대각방향의 상류효과를 포함시켜 시간에 대한 2차 정확도를 갖도록 하였다. 또한 이 방법을 유량보정수송(FCT)법과 결합시켜 해의 단조성을 보장하였다. 몇 가지 단순 문제에 대한 시험 결과 이 기법이 수치오차에 의한 계면형상의 변형과 파손올 감소시킴을 확인하였다.
마이크로/나노 채널에서의 비평형 전기삼투 유동 모사를 위한 수치모델
곽호상(Ho Sang Kwak),E. F. Hasselbrink 한국전산유체공학회 2004 한국전산유체공학회 학술대회논문집 Vol.2004 No.-
A finite volume numerical model is developed for simulating non-equilibrium electroosmotic flow in micro- and nanochannels. The Guoy-Chapman model is adopted to compute the flow and electric potential. The Nernst- Planck equation is employed to trace unsteady transports of ionic species, i.e., time-dependent net charge density. A new set of boundary conditions based on surface charge density are designed rather than using the conventionally-employed zeta potential. A few issues for an efficient computation of electroosmotic flows are discussed. Representative computational examples are given to illustrate the robustness of the numerical model.
곽호상(Ho Sang Kwak) 한국전산유체공학회 1997 한국전산유체공학회 학술대회논문집 Vol.1997 No.-
A parallel implementation is made of a two-dimensional finite volume model based on the SIMPLER. The solution domain is decomposed into several subdomains and the solution at each subdomain is acquired by parallel use of multiple processors. Communications between processors are accomplished by using the standard MPI and the Cray-specific SHMEM. The parallelization method for the overall solution procedure to the Navier-Stokes equations is described in detail. The parallel implementation is validated on the Cray T3E system for a benchmark problem of natural convection in a sidewall-heated cavity. The parallel performance is assessed and the issues encountered in achieving a high-performance parallel model are elaborated.
급속냉각이 가능한 고온 엠보싱 나노식각 장비용 열판의 설계
곽호상(Ho Sang Kwak),박규진(Gyu Jin Park),손병철(Byung Chul Sohn),이재종(Jae Jong Lee),박희창(Hee Chang Park) 한국생산제조학회 2006 한국공작기계학회 춘계학술대회논문집 Vol.2006 No.-
A hot plate device has been designed as a thermal treatment tool for the press-type hot embossing machine which copies the nanopatterns on stamp to polymer substrate. Design goal is to achieve the performance of rapid heating and cooling as well as high temperature uniformity and the strength to endure high stamping pressure. Analysis of design requirements leads to a new hot plate configuration having cooling holes and catridge heaters which are straight and arranged in parallel for extensibility toward large area. Numerical computations have been conducted for assessing the feasibility of the proposed design cencept and for determining the optimal distribution of heating and cooling elements. The numerical results and raised issues are scrutinized in view of accomplishment of rapid heating and cooling together with high temperature uniformity.
이중원통형 유체층에서 용기의 회전이 열모세관 유동에 미치는 영향
곽호상(Ho Sang Kwak),우마로프알리세르(Alisher Umarov),김경진(Kyoungjin Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
A numerical study is conducted on thermocapillary flow of thin fluid layer in an annulus with an imposed horizontal temperature difference. In this flow configuration simulating a semiconductor materials processing, the flow is affected by the interaction between buoyancy and surface tension. In a very thin fluid layer, hydrothermal waves occur due to the dominant thermocapillary force. In a relatively thick fluid layer, the flow exhibits long convective rolls formed due to the buoyant flow instability. As a means to suppress these three-dimensional instabilities, rotation of the system is introduced. Numerical results show that the careful use of rotation may be an efficient way to reduce or eliminate hydrothermal waves. For the buoyancy-domanated flow regime, the rotation suppresses the growth of convective instability, but it may invoke other type of three-dimensional waves driven by baroclinic instability.
An Accurate Advection Scheme for the Volume Fraction of an Incompressible Fluid
곽호상(Ho Sang Kwak),Kunio Kuwahara 한국전산유체공학회 1997 한국전산유체공학회 학술대회논문집 Vol.1997 No.-
비압축성 유체의 혼합유동장에서 유체간 경계 형상의 변화를 계산하기 위한 수치기법을 개발하였다. VOF방법에 기초하여 한 유체의 점유체적비의 이동방정식을 풀기 위한 새로운 대류항 계산법을 제안하였다. 유동에 대한 경계면의 방향을 고려하여 풍상법과 역풍상법의 적절한 조합을 취하였고 대각방향 성분의 영향을 고려함으로써 시간에 대한 정확도를 2차로 증가시켰다. 또한 이 방법을 유속보정법(FCT)과 결합시켜 해의 단조성을 보장하였다. 두 가지 단순 문제를 통하여 제안된 기법의 정확성과 신뢰성을 시험,검증하였다.
곽호상(Ho Sang Kwak),현재민(Jae Min Hyun) 한국전산유체공학회 1997 한국전산유체공학회 학술대회논문집 Vol.1997 No.-
Unsteady natural convection of an enclosed fluid has been one of the fundamental thermo-fluid problems, of which dynamic relevance is found in many engineering applications. Together with the inherent coupling between the boundary layers and the interior core, and strong interaction between flow and temperature fields, the unsteadiness poses serious hurdles for analytical and experimental approaches. With the recent development of computers and solution algorithms, computational fluid dynamics has become the prevailing tool to tackle the underlying problems. In this presentation, a few examples of numerical studies are introduced. The usefulness and potential of numerical simulations in investigating unsteady natural convection are elaborated.
영역 분할에 의한 SIMPLER 모델의 병렬화와 성능 분석
곽호상(Ho Sang Kwak),이상산(Sangsan Lee) 한국전산유체공학회 1998 한국전산유체공학회지 Vol.3 No.1
Parallel implementation is conducted for a SIMPLER finite volume model. The present parallelism is based on domain decomposition and explicit message passing using MPI and SHMEM. Two parallel solvers to tridiagonal matrix equation are employed. The implementation is verified on the Cray T3E system for a benchmark problem of natural convection in a sidewall-heated cavity. The test results illustrate good scalability of the present parallel models. Performance issues are elaborated in view of convergence as well as conventional parallel overheads and single processor performance. The effectiveness of a localized matrix solution algorithm is demonstrated.