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정압기 임계유동특성 및 배관망해석 요소로서의 고려에 관한 수치해석적 연구 (II) : 단면적 및 개도 변화
신창훈(C. H. Shin),하종만(J. M. Ha),이철구(C. G. Lee),허재영(J. Y. Her),임지현(J. H. Im),주원구(W. G. Joo) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
The major parameters governing the fluid dynamical and thermo-dynamical behavior in the large pipeline network system are friction loss and the pipeline length. But in local pipeline networks and relatively short distance pipeline system, secondary loss and the considerations of the moving states of the fluid machine are also important. One of the major element in local pressure control system is pressure regulator. It causes the variations of the physical properties in that pipeline system. When it is under working, the accurate analysis of the flow properties is so difficult. In this study, some numerical approaches to investigate the critical-flow-characteristics of the pressure regulator have been done according to the variations of the opening ratio or cross-sectional area and the detail examinations and considerations of the pressure regulator as a pipeline network elements have been carried. Finally the flow-flied distributions and critical-flow-characteristics have been presented in detail and the critical flow phenomena and the relation to the opening ratio or cross-sectional-area ratio have been studied.
터널에 진입하는 고속전철에 의한 3차원 점성유동과 압축파 특성에 관한 수치해석적 연구
신창훈(C. H. Shin),박원규(W. G. Park) 한국전산유체공학회 2000 한국전산유체공학회 학술대회논문집 Vol.2000 No.5
The three-dimensional unsteady compressible Full Navier-Stokes equation solver with sliding multi-block method has been applied to analyze three dimensional characteristics of the flow field and compression wave around the high speed train which is entering into a tunnel. The numerical scheme of AF + ADI was used to efficiently solve Navier-Stokes equations in the curvilinear coordinate system. The vortex formation around the nose region was found and the generation of compression wave due to the blockage effects was observed ahead of the train in the form of plane wave. The three dimensional characteristics of the flow field compared to the analytic results were discussed in detail. The variation of pressure of tunnel wall surface and velocity profile of the train are identified as the train enters into a tunnel. The changes in aerodynamic forces and streamlines of each specific sections are also discussed and presented.
신창훈(C.H. Shin),박원규(W.G. Park) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.11
Shale gas reservoir flow shows very complex and abstruse behavior due to mixing among porous flow normally shown in conventional oil and gas reservoirs and fracture network flow through natural fractures and artificial fractures induced by hydraulic fracturing and diffusion flow in a very tight rock matrix. Therefore, the establishment of proper analysis theory and method to examine shale gas reservoir flow is earnest. For this, we tried to devise the new flow equation simulating the complex flow simultaneously, and to present the finite governing equations by FDM transformation, and then to establish numerical analysis method for the complex flow in this study. For a start, we tried to revise the porous media flow equation to the new flow equation by considering the Darcy-Weisbach relation. As a result, the permeability of porous media can be estimated by considering the effects related to the geometric shape of pore in porous media based on the permeability of internal pipe flow. We defined this as the equivalent porous media permeability, and presented the relation with devising the equivalent section area required for the calculation and defining the equivalent coefficient of pore shape. Additionally, we presented the modified Darcy equation and the governing equation system of porous flow with adopting the equivalent permeability and equivalent section area concepts, and then showed the discretized governing equation system for numerical analysis. Finally, the validity was confirmed by the CFD analysis using the presented governing equation system for the complex flow in the shale gas reservoir.
균열과 다공질 유동의 특성 규명을 위한 수치해석적 연구
신창훈(C.H. Shin),박원규(W.G. Park) 한국전산유체공학회 2013 한국전산유체공학회 학술대회논문집 Vol.2013 No.5
Recently, commercial development of unconventional gas resources including shale gas is being rapidly expanded, centring in North America. For developing these very tight shale gas formations, both long reach horizontal drilling and multi-stage hydraulic fracturing techniques are required. It is possible to produce natural gas by means of the artificial fracture networks created by these techniques. Consequently, the flow in a shale gas reservoir exhibits a very complex flow behaviour, compounded with pipe flows in vertical and horizontal wells, reaching generally 4 to 7 km in distance, diffusion flows in very tight shale rock matrices, porous flows in sand formations and propant banking areas, and fracture network flows through both natural fractures and hydraulic fractures in a shale formation. Therefore, it is required to devise and apply new reservoir flow analysis theory and methods which can accurately consider complex gas flow owing to the geometric characteristics and distributions of various pores and flow paths within a shale gas reservoir. Particularly, a new analysis method which can properly simulate fracture and porous flows having various ranges of porosity and permeability should be necessarily proposed. Hence, in this study, the influences of convection and diffusion forces in the momentum equation for porous flow, the core factors inducing the flow differences between the general range of porosity and permeability in normal porous media and the high range of that in fractures and so on, were closely examined by CFD method. Finally, it was tried to quantify them by each porosity and permeability range of various porous media and to be linked to a new analysis method to distinguish and compound fracture and porous flows.