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안상준(S. J. Ahn),오형우(H. W. Oh),김광용(K. Y. Kim) 한국유체기계학회 2001 유체기계 연구개발 발표회 논문집 Vol.- No.-
This paper presents analysis of the flows through three different types of radial compressor impeller by using quasi-three-dimensional analysis method. The method obtains two-dimensional solution for velocity distribution on meridional plane, and then calculates approximately the static pressure distributions on blade surfaces. Finite difference method is used for the solutions of governing equations. The compressors have low level compression-ratio and 12 straight radial blades with no sweepback. The results are compared with experimental data and the results of inviscid analysis with finite element method. It can be concluded that the agreement is good for the cases where viscous effects are not dominant.
비정렬 격자계에서 균질혼합 모델을 이용한 선박 프로펠러 주위의 캐비테이션 유동 해석
안상준(S.J. Ahn),권오준(O.J. Kwon) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
In this paper, the cavitating flows around a marine propeller have been numerically investigated by using a 3-d multi-phase RANS flow solver based on pseudo-compressibility and a homogeneous mixture model on unstructured meshes. For this purpose, a vertex-centered finite-volume method was utilized in conjunction with 2nd-order Roes FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing. The kω-SST model was employed for the closure of turbulence. The Gauss-Seidel iteration was used for time integration. The phase change rate between the liquid and vapor phases was determined by Merkles cavitation model based on the difference between local and vapor pressure. Calculations were made for the P4381 marine propeller with different cavitation numbers at several advancing ratios. The cavity structure, such as size and shape, was well captured. Reasonable agreements were obtained between the present results and the experiment for the integrated blade loadings such as thrust and torque. The observation of the loading breakdown behavior was also made.
비정렬 격자계에서 균질혼합 모델을 이용한 2차원 수중익형 주위의 캐비테이션 유동 해석
안상준(S.J. Ahn),권오준(O.J. Kwon) 한국전산유체공학회 2012 한국전산유체공학회지 Vol.17 No.1
In this paper, the cavitating flows around a hydrofoil have been numerically investigated by using a 2-d multi-phase RANS flow solver based on pseudo-compressibility and a homogeneous mixture model on unstructured meshes. For this purpose, a vertex-centered finite-volume method was utilized in conjunction with 2nd-order Roe’s FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing. The Spalart-Allmaras one equation model was employed for the closure of turbulence. A dual-time stepping method and the Gauss-Seidel iteration were used for unsteady time integration. The phase change rate between the liquid and vapor phases was determined by Merkle’s cavitation model based on the difference between local and vapor pressure. Steady state calculations were made for the modified NACA66 hydrofoil at several flow conditions. Good agreements were obtained between the present results and the experiment for the pressure coefficient on a hydrofoil surface. Additional calculation was made for cloud cavitation around the hydrofoil. The observation of the vapor structure, such as cavity size and shape, was made, and the flow characteristics around the cavity were analyzed. Good agreements were obtained between the present results and the experiment for the frequency and the Strouhal number of cavity oscillation.
나노세컨드 펄스 DBD 플라즈마의 멀티스케일 모델링을 위한 비평형 플라즈마 유동 해석 및 검증
안상준(S. Ahn),채정헌(J. Chae),김형진(H.J. Kim),신진영(J.Y. Shin),김규홍(K.H. Kim) 한국전산유체공학회 2019 한국전산유체공학회지 Vol.24 No.1
In a nanosecond pulse discharge, the computational cost is high because of the characteristic time difference between the plasma and the flow. In order to reduce the computational cost, multi-scale modeling study of nanosecond pulse discharge plasma is needed. In this study, we developed and verified a non-equilibrium plasma solver for nanosecond-pulse Dielectric Barrier Discharge(NS-DBD) multi-scale modeling study. To simulate the non-equilibrium phenomena, 17 chemical species / 54 chemistry reaction models were used. The governing equations included chemical species continuity equations, a electrical potential equation, and Navier-Stokes equations. Numerical results show that streamer velocity and micro shock wave speed are comparable to those of other experimental results. This study is expected to contribute to the future study of NS-DBD multi-scale modeling.