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가압축성 기법을 이용한 비정렬 격자상에서의 비압축성 점성해석
문영준(Young J. Moon) 한국전산유체공학회 1995 한국전산유체공학회 학술대회논문집 Vol.1995 No.-
Viscous analysis on incompressible flows is performed using unstructured triangular meshes. A twodimensional and axisymmetric incompressible Navier-Stokes equations are solved in time-marching form by artificial compressibility method. The governing equations are discretized by a cell-centered based finitevolume method, and a centered scheme is used for inviscid and viscous fluxes with fourth order artificial dissipation. An explicit multi-stage Runge-Kutta method is used for the time integration with local time stepping and implicit residual smoothing. Convergence properties are examined and solution accuracies are also validated with benchmark solution and experiment.
벽면 전단 유동의 공력 소음 해석을 위한 유동-음향 분리 기법
서정희(J. H. Seo),문영준(Young J. Moon) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Aeolian tone generation from a two dimensional circular cylinder is numerically investigated via<br/> direct numerical simulation and hydrodynamic-acoustic splitting method. All governing equation are<br/> spatially discretized with the sixth-order compact scheme and fourth-order Runge-Kutta method to avoid<br/> excessive numerical dissipations and dispersions of acoustic quantities. Comparisons of two results show<br/> that the previous splitting method can not accurately predict the aeroacoustic noise of wall bounded<br/> shear flow. In this study, a perturbation viscous term and a new energy equation have been developed.<br/> This modified splitting method accurately predicts aeroacoustic noise from wall-bounded shear flow. The<br/> present results agree very well with the direct numerical simulation solution.
조용,문영준,박진무,Cho, Yong,Moon, Young J.,Park, Jin-Moo 대한설비공학회 2001 설비공학 논문집 Vol.13 No.7
The flow induced noise of the cross-flow fan with uniform/random pitch blades is predicted by computational methods. With the time dependent surface pressure data obtained by solving the incompressible Navier-Stokes equations in moving coordinates, the acoustic pressure is predicted by the Ffowcs Williams-Hawkings equation. The positions of the blade noise source are identified through an investigation of the acoustic pressure history induced by one blade, and it is confirmed that the dominant noise source is near the stabilizer. Since the acoustic pressure of the random pitch fan fluctuates according to the blade passin, the dominant BPF noise of the uniform pitch fan is modulated into some reduced discrete noises which have multiples of a 50Hz difference from BPF.
비정상 점성유동 해석에 의한 부등피치 횡류홴의 BPF 순음 주파수 변조 특성 예측
조용,문영준,Cho, Yong,Moon, Young J. 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.3
The unsteady flow characteristics and associated blade tonal noise of a cross-flow fan are predicted by computational methods. The incompressible Navier-Stokes equations are time-accurately solved for obtaining the pressure fluctuations between the rotating blades and the stabilizer. and the sound pressure is predicted using Curie's equation. The discrete noise characteristics of three impellers with a uniform and two random pitch (type-A and -B) blades are compared by their SPL (Sound Pressure Level) spectra. and the frequency modulation characteristics of the BPF (Blade Passing Frequency) noise are discussed. Besides. a mathematical model is proposed for the prediction of discrete blade tonal noise and is validated with available experimental data. The fan performance is also compared with experimental data. indicating that the random pitch effect does not significantly alter the performance characteristics at ${\phi}$ 〉 0.4
장재영(Jae Young Jang),문영준(Young J. Moon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Fluid-structure interactions(FSI) of an elastic cantilever are numerically predicted to analyze the characteristics of the cantilever and induced sound field under various cantilever properties. A moving-grid based system and 6th-order compact scheme are adopted, which is based on non-conservative form of Navier-Stokes equation. First, a flow field is simulated with an immovable cantilever. Through this simulation, the basic information of a flow instability is obtained. Then forced-vibration simulation is performed, to understand the behavior of the elastic cantilever. After these simulations, FSI results are shown, which is treating both the flow field and the elastic cantilever simultaneously. These results report that the movement of beam reduces sound considerably.
비압축성 점성유동 해석에서의 Multi-Stage Runge-Kutta 기법의 수렴특성 연구
박원찬(Won C. Park),문영준(Young J. Moon) 한국전산유체공학회 1997 한국전산유체공학회 학술대회논문집 Vol.1997 No.-
Objective of the present study is to examine the convergence characteristics of the various multi-stage Runge-Kutta methods in solving the incompressible Navier-Stokes equations of a time-marching form casted by the artificial compressibility method. Convergence characteristics are examined over 2-stage, 4-stage and hybrid type (using 4-, 3-, 2-stages sequentially) Runge-Kutta methods for a laminar lid-driven cavity flow, and also for a turbulent bump channel flow using Chien's low-Reynolds number turbulence model. Efforts are made to establish a stable and fast convergent multi-stage Runge-Kutta method with minimal artificial dissipations.
Counter-Rotating Streamwise Vortex Formation in the Turbine Cascade with Endwall Fence
고성룡(Seong Ryong Koh),문영준(Young J. Moon) 한국전산유체공학회 1999 한국전산유체공학회 학술대회논문집 Vol.1999 No.-
The three-dimensional turbulent cascade flows with and without endwall fences are numerically investigated by solving the incompressible Navier-Stckes equations with a high-Reynolds number k-ε turbulence closure model. A projection method based algorithm is used in the finite-volume formulation, with the second order upwind-differencing scheme for the convective terms. First, assessments on accuracy of the present method are made by comparing the static pressure distributions at the mid-span of the cascade with measured data, and also by confirming the experimental observations on the choice of an optimal fence height for the secondary flow control. In understanding the three-dimensional nature of the secondary flow in turbine cascade, the limiting streamline patterns and the static pressure contours at the suction surface of the blade as well as on the cascade endwall are employed to visualize the effectiveness of the endwall fence for the secondary flow control. Analysis on the streamwise vorticity contour maps along the cascade with the three-dimensional representation of their iso-surfaces reveals the structure of the complicated vortical flow in the turbine cascade with endwall fence, and also leads to an understanding on formation of the counter-rotating streamwise vortex over the endwall fence, in explaining the mechanisms of controlling the secondary flow and also for the proper selection of an optimal fence height.
비구조형 삼각형 격자에 대한 SMAC기법을 이용한 비압축성 나비어-스톡스 방정식 해법 개발
남현식(Hyeun S. Nam),문영준(Young J. Moon) 한국전산유체공학회 1997 한국전산유체공학회 학술대회논문집 Vol.1997 No.-
An unstructured finite volume method is presented for seeking steady and unsteady flow solutions of the two-dimensional incompressible viscous flows. In the present method, SMAC-type algorithm is implemented on unstructured triangular meshes, using second order upwind scheme for the convective fluxes. Validation tests are made for various steady and unsteady incompressible flows. Convergence characteristics are examined and accuracy<br/> comparisons are made with some benchmark solutions.