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예조건화된 압축성유동 수치기법에서의 풍상차분법의 수치특성 검토
길재흥(J. H. Gill),이두환(D. H. Lee),최윤호(Y. H. Choi),권장혁(J. H. Kwon),이승수(S. S. Lee) 한국전산유체공학회 2002 한국전산유체공학회 학술대회논문집 Vol.2002 No.-
Studies of the numerical characteristics of implicit upwind. schemes, such as upwind ADI, Line Gauss-Seidel(LGS) and Point Gauss-Seidel(LU) algorithms, for preconditioned Navier-Stokes equations are performed. All the algorithms are expressed in approximate factorization form and Van Neumann stability analysis and convergence studies are made. Preconditioning is applied for efficient convergence at low Mach numbers and low Reynolds numbers. For high aspect ratio computations, the ADI and LGS algorithms show efficient and uniform convergence up to moderate aspect ratio if we adopt viscous preconditioning based on min-CFL/max-VNN time-step definition. The LU algorithm, on the other hand, shows serious deterioration in convergence rate as the grid aspect ratio increases. Computations for practical applications also verify these results.
오픈 소스 CFD 코드를 이용한 차세대 고속열차 공력 해석
김병윤(B.Y. Kim),길재흥(J.H. Gill),권혁빈(H.B. Kwon) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
CFD simulation is widely used in various industries, universities and research centers. In Korea most of the researchers use foreign commercial S/W packages especially in industries. But commercial CFD packages have some problems as limit to source code and very high license fee. So from several years ago open source CFD code has been widely spread as an alternative. But in Korea there are a few users of open source code. Insufficiency of performance validation as for accuracy, robustness, convenience and parallel speed-up is important obstacles of open source code. So we tested some validation cases as to incompressible external aerodynamics and internal flows and now are doing compressible flows. As the first stage of compressible flow validation, we simulated Korea next generation high speed train(HEMU). It’s running condition is 400㎞/hr and maximum Mach number reaches up to 0.4. With the high speed train we tested accuracy, robustness and parallel performance of open source CFD code OpenFOAM. Because there isn’t experimental data we compared results with widely used commercial code. When use 1<SUP>s</SUP> <SUP>t</SUP>order upwind scheme aerodynamic forces are very similar to commercial code. But using 2<SUP>nd</SUP> order upwind scheme there was some discrepancy. The reason of the difference is not clear yet. Mesh manipulation, domain decomposition, post-processing and robustness are satisfactory. Paralle lperformance is similar to commercial code.
오픈소스 CFD 코드 오픈폼(OpenFOAM)을 이용한 가스터빈엔진 노즐-터빈 유동 해석
김병윤(B.Y. Kim),김병휘(B.H. Kim),길재흥(J.H. Gill) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
OpenFOAM is widely used open source CFD code. In this study the performance of OpenFOAM to simulate nozzle-turbine flow is evaluated. Single stage nozzle-turbine of radial gas turbine engine is simulated. To simulate nozzle-turbine flow, the capability of compressible flow, MRF, cylic boundary condition and non-matching grid interface are needed. snappyHexMesh of OpenFOAM is used to generate mesh and steady DensityBasedTurbo solver of OpenFOAM-1.6-ext is used for flow compressibility, cyclic난gi boundary condition is used, and overlapGgi method for non-matching grid interface between nozzle and turbine. We compared results of OpenFOAM with commercial CFD code. OpenFOAM shows enough capability for industrial turbine simulation and shows some advantages and disadvantages comparing to commercial CFD code.