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다양한 형태의 미소 채널에서 격자 볼츠만 방법을 이용한 이상 유동 해석
변성준(Sing-jun Byun),윤준용(Joon-Yong Yoon),이도형(Do-Hyung Lee) 한국유체기계학회 2007 유체기계 연구개발 발표회 논문집 Vol.- No.-
This research investigates the lengths of droplets and the spatial periods between droplets in micro channels of having separately different entrance types. The entrance types of micro-channels are T-type, cross type and Y-type, Lattice Boltzmann method is used for analysis. Interaction potential LBM proposed by Shan and Chen appears to be effective for immiscible two-phase flow in micro channel. Experimental data by Joshua D. Tice el al is found to be in good agreement with values obtained from simulations. As a result of simulation, the sizes of droplets are most small and the period between droplets are most short in cross type. The formations of droplet are influenced by the ratio of flow rate and shapes of inlets.
격자 볼츠만 방법을 이용한 난류 경계층에서의 오염물질 확산에 대한 수치적 연구
김준형(Joon-Hyung Kim),윤준용(Joon-Yong Yoon),변성준(Sung-Joon Byun),신명섭(Myung-Seob Shin) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
The purpose of this study is a numerical simulation of pollutant-laden flow in a boundary layer. The pollutant source is divided Ground-Level Source (GLS) and Elevated source (ES). Air velocity and pollutant particle concentration profile is compared with the experiments in a turbulent boundary layer flow. The code for this research uses Large-Eddy Simulation (LES) model by using Lattice Boltzmann Method (LBM). The Lattice Boltzmann subgrid model predicts more exact solution than previous Reynolds-Averaged Navier-Stokes (RANS) model.
고차압 제어용 글로브 밸브 트림 내부의 3차원 유동장 해석
윤준용,변성준,양재모,이도형,Yoon, Joon-Yong,Byun, Sung-Joon,Yang, Jae-Mo,Lee, Do-Hyung 한국유체기계학회 2001 한국유체기계학회 논문집 Vol.4 No.3
Numerical analysis of the three dimensional turbulent flow field in a complex valve trim is carried out to confirm the possibility whether this simulation tool can be used as a design tool or not. The simulation of the incompressible flow in a glove valve is performed by using the commercial code. CFD-ACEA utilizes the finite volume approach as a discretization scheme, and the pressure-velocity coupling is made from SIMPLEC algorithm in it. Four flow cases of the control valve are investigated, and the valve flow coefficient for each case is compared with the experimental data. Simulation results show a good agreement with the experiments, and it is observed that the cavitation model improves the simulation results.
윤준용,맹주성,변성준,이상환,Yoon, Joon-Yong,Maeng, Joo-Sung,Byun, Sung-Joon,Lee, Sang-Hwan 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.7
Numerical study of three-dimensional turbulent flow in a forward curved centrifugal fan is presented. Standard $k-{\varepsilon}$ turbulence model and non-orthogonal curvilinear coordinates arc used to consider the turbulent flow field and complex geometry. Finite Volume approach is adopted for discretization scheme and structured grid system is used to help convergence. Multiblock grid system is used for flow field and divided into five domains that are inlet, outlet, impeller, tip clearance and scroll. It is assumed that the flow field is steady and incompressible. These numerical results are compared with the experimental data inside a rotor and at the fan outlet. Most important flow features are captured through this numerical approach. Finally details of flow field inside a fan are described and analyzed.
표면 거칠기 효과를 고려한 2-방정식 난류 모델의 성능평가
윤준용,천정민,강승규,변성준,Yoon, Joon-Yong,Chun, Jung-Min,Kang, Seung-Kyu,Byun, Sung-Joon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.12
The effect of roughness is a change in the velocity and turbulence distributions near the surface. Turbulence models with surface roughness effect are applied to the fully developed flow in a two-dimensional, rough wall channel. Modified wall function model, low-Reynolds number k-$\varepsilon$ model, and k-$\omega$ model are selected for comparison. In order to make a fair comparison, the calculation results are compared with the experimental data. The modified wall function model and the low-Reynolds number k-$\varepsilon$ model require further refinement, while the k-$\omega$ model of Wilcox performs remarkably well over a wide range of roughness values.
신명섭(Myung Seob Shin),변성준(Sung Jun Byun),윤준용(Joon Yong Yoon) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.5
본 연구에서는 격자볼츠만 방법(LBM)을 이용하여 미소채널 내의 유동이 완전 발달 층류유동일 때, 미소 채널 내에서의 표면 거칠기 영향에 대하여 수치계산을 수행하였다. 미소채널 내에서 표면 거칠기의 영향을 분석하기 위하여 표면 거칠기의 높이(ε), 폭(w), 간격(s)을 조절하여 미소채널에서의 마찰계수(f), 포와이즈수(Po)와 거시적 이론값과 비교하였다. 미소채널에서의 표면 거칠기의 높이가 증가함에 따라 거시적 이론값(Po=24)에 비해서 수치해석으로부터 예측된 값(25 Po 29)이 높게 나타났으며, 표면 거칠기의 폭과 간격은 표면 거칠기의 높이에 비해 미소채널 내부 유동의 변화에 큰 영향을 주지 않는 것을 알 수 있었다. 이 결과로부터 미소채널 내부 유동에서는 표면 거칠기의 영향으로 거시적 층류유동과는 다른 유동현상이 나타난다는 것을 알 수 있었다. In this paper, lattice Boltzmann method(LBM) results for a laminar flow in a microchannel with rough surface are presented. The surface roughness is modeled as an array of rectangular modules placed on the top and bottom surface of a parallel-plate channel. The effects of relative surface roughness, roughness distribution, and roughness size are presented in terms of the Poiseuille number. The roughness distribution characterized by the ratio of the roughness height to the spacing between the modules has a negligible effect on the flow and friction factors. Finally, a significant increase in the Poiseuille number is observed when the surface roughness is considered, and the effects of roughness on the microflow field mainly depend on the surface roughness.
격자볼츠만 방법을 이용한 도심지역 오염물질 확산에 대한 수치적 연구
정재화(Jae-Hwa Jung),변성준(Sung-Jun Byun),신명섭(Myung-Seob Shin),윤준용(Joon-Yong Yoon) 한국유체기계학회 2007 유체기계 연구개발 발표회 논문집 Vol.- No.-
The pollutant dispersion in a street canyon has been described in this study by using an two-dimensional lattice Boltzmann method coupled to the Smagorinsky sub-grid scale model. The pollutant source is divided ground-level source(Gl.S) and elevated source (ES). The obstacles were made a flat plate. The height of obstacle and distance of them were divided flow patterns as a isolated roughness flow, wake interference flow, skimming flow. The influence of the ratio between the height of the upstream and downstream canyon obstacles, as well as the gap distance between them was analyzed considering the situation of 'open country' and 'urban roughness'. The code for this research used large eddy simulation(LES) model by using lattice Boltzmann method(LBM).
격자볼츠만 아격자 모델을 이용한 난류 경계층 내에서의 오염물질 확산에 대한 수치적 연구
신명섭(Myung Seob Shin),변성준(Sung Jun Byun),김준형(Joon Hyung Kim),윤준용(Joon Yong Yoon) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.2
격자볼츠만 방법(LBM)을 이용하여 난류 경계층에서의 오염물질 확산에 대하여 수치계산을 수행하였다. 난류 경계층 내의 유동을 모사하기 위하여 격자볼츠만 방법에 Smagorinsky 아격자 모델을 적용한 LB-SGS 모델을 사용하였으며, 오염물질의 확산을 모사하기 위하여 Passive-scalar 방법을 적용하였다. LB-SGS 모델의 신뢰성 검증을 위하여 Fackrell & Robins(1982)과 Raupach & Legg(1983)의 실험 조건과 동일한 조건하에서 수치계산을 수행하였고, 수치계산으로 얻어진 농도 분포를 실험값과 비교하였다. 이 결과로부터 LB-SGS 모델이 난류 경계층 내에서의 오염물질의 농도분포를 예측하는데 적합한 모델임을 알 수 있었다. The dispersion of a pollutant in a turbulent boundary layer has been described in this study by using a two-dimensional lattice Boltzmann method (LBM) and the Smagorinsky sub-grid-scale (SGS) model. The scalar transport equation corresponding to the pollutant concentration is adopted; the pollutant is considered to be in a continuous phase. The pollutant source is classified as ground-level source (GLS) and elevated-point source (ES). Air velocity and particle concentration profile for the pollutant are compared with the respective results and profiles obtained in the experiments of Fackrell and Robins (1982) and Raupach and Legg (1983). The numerical results obtained in this study, i.e., the simulation and the experimental data for the mean flow velocity profiles and the pollutant concentration profiles, are in good agreement with each other.