• 한국환경과학회지
• /
• 제9권1호
• /
• pp.13-18
• /
• 2000

The purpose of this study is to estimate the low-flow statistics at the mountainous watershed. The formulation for the estimation of the design low-flow statistics was obtained by means of a hydraulic approach applied to a simple conceptual model for a mountainous watershed. Three of the independent variables associated with the low-flow statistics is watershed area(A), average basin slope(S) and the base flow recession constant(K); Watershed area was measured from topographic maps and average basin slope is approximated in this study using Strahler's slope determining method. And base flow recession constant computed using Vogel and Kroll's method. Unfortunately, this method is usually unavailable at ungaged sites. In this study, recession constant at ungaged sites is estimated using graphical regression method used by Giese and Mason. The model for estimating low-flow statistics were applied to all 61 catchments in the Sumjin, Mankyung basin.

• 대한지하수환경학회지
• /
• 제7권1호
• /
• pp.8-14
• /
• 2000

오늘날 급격한 산업화, 도시화, 인구증가 등으로 용수수요 급증, 수질오염 수자원 개발의 한계, 용수공급의 안정성 등으로 인하여 갈수량에 관한 관심이 증대하고 있다. 물리적 토대를 둔 유로-대수층 모형을 이용하여 영산강 유역에 위치하고 있는 주요하천의 지역 갈수 유출모형의 개발을 모색하였다. 이를 위하여 영산강 유역의 주요하천에서 23개의 대상 소유역을 선정하였으며, 여기서 갈수량을 측정하여 본 연구의 모형개발에 이용하였다. 그리고 최종적으로 영산강 유역의 미계측 지점에서 갈수량을 추정하기 위한 지역갈수 유출 모형을 제안하였다.

• 국제초고층학회논문집
• /
• 제2권2호
• /
• pp.105-113
• /
• 2013

Recent studies proved turbulent flow properties in high-rise building models differ from those in low-rise building models by comparing turbulent statistics. Although it is important to understand the flow characteristics within and above high-rise building models in the study of urban environment, it is still unknown and under investigation. For this reason, we performed wind tunnel experiment using Particle Image Velocimetry (PIV) to investigate and identify the turbulent flow properties and characteristic flow patterns in high-rise building models. In particular, we focus on instantaneous flow field near the canopy and extracted flow field when homogeneous flow field were observed. As a result, six characteristic flow patterns were identified and the relationship between these flow patterns and turbulent organized structure were shown.

• 대한지리학회지
• /
• 제47권2호
• /
• pp.268-281
• /
• 2012

인구이동통계는 사회현상에 대한 공간적 이해와 공간과정의 사회적 영향 파악에 유용한 정보를 제공해줌에도 불구하고 데이터 구조의 복잡성 때문에 자료 서비스와 분석이 제한되어 왔다. 한편 인구이동통계를 탐색하고 시각화하는 효과적인 방법인 유선도 작성(flow mapping)은 아직 상용 GIS 소프트웨어서 완전히 구현되지 못하고 있다. 이에 본 연구의 목적은 Web GIS를 통한 유선도 제작과 이를 이용한 인구이동통계에 대한 탐색적 공간 분석이 가능함으로 보여주는 것이다. 데이터베이스, GIS, 지도학적 관점에서 인구이동통계의 특성을 고찰하였고, 이를 바탕으로 O-D 구조의 인구이동통계를 유선도 제작에 적합한 공간데이터로 변환하였다. 인구이동통계에 적합하도록 Web GIS의 사용자 인터페이스를 전문화하였고, 지도화의 시간, 공간 및 속성 범위의 설정을 통한 탐색적 시각화가 가능하도록 구성하였다.

• Journal of Magnetics
• /
• 제21권2호
• /
• pp.273-280
• /
• 2016

In this paper, the peristaltic flow of Psedoplastic fluid with variable viscosity in an asymmetric channel is examined. The bionic effects by means of magnetohydrodynamics (MHD) are taken into account. The assumptions of long wave length and low Reynolds number are taken into account. The basic equations governing the flow are first reduced to a set of ordinary differential equation by using appropriate transformation for variables and then solve by using perturbation method. The effect of physical parameters on the pressure rise, velocity and pressure gradient are illustrated graphically. The trapping phenomenon is analyzed through stream lines. A suitable comparison has also been made as a limiting case of the considered problem.

• Journal of the Korean Physical Society
• /
• 제73권9호
• /
• pp.1295-1302
• /
• 2018

In the present investigation, we have studied the magnetohydrodynamic (MHD) heat transfer of peristaltic flow in a tube. The analysis is made without imposing any assumption to obtain the streamline and isothermal line directly. Galerkin's finite element method has been used on the governing Navier-Stoke's equation in the form of ${\psi}-{\omega}$. The graphs of the computed longitudinal velocity, temperature and pressure are plotted against different value of the emerging parameter by using the stream function and vorticity. The results are valid beyond the long wavelength and the low Reynolds number limits. We conclude that higher values of the parameters are not independent of the time mean flow rate.

• 대한기계학회논문집B
• /
• 제25권7호
• /
• pp.944-951
• /
• 2001

The purpose of this study is to investigate the effect of shear on turbulent diffusion. Turbulent Couette flows at low Reynolds number are numerically simulated using a Lagrangian PDF method. Flow field and particle trajectories are computed and analyzed in detail. Statistics for particle dispersion obtained from numerical simulations is compared with the classical scaling relations for dispersion in a shear flow.

• 가정과삶의질연구
• /
• 제32권5호
• /
• pp.125-143
• /
• 2014

The purpose of this study was to gain a better understanding of households with a negative cash flow. The Household Budget Survey conducted in 2000, 2005, and 2010 by the Bureau of Statistics in South Korea were used for this study. The households used in this study were divided into four groups according to their income levels; they were categorized the lowest, low, middle, and high income groups. This study made several findings regarding households with a negative/positive cash flow. Firstly, the demographic and economic characteristics were different between those who have a negative cash flow and those with a positive cash flow. A female household head, a household head age 65 and older, a household head with a lower educational attainment, an unemployed household head, and the presence of a child/children in schools were related with the household deficit. Secondly, the households with a positive cash flow had a higher income level compared to the households with a negative cash flow, while the households with a negative cash flow had a much higher consumption level compared to the households with a positive cash flow. Thirdly, the household deficit to total income ratio of the lowest income group was higher when compared to any other income group. Lastly, the multivariate statistics showed that households including a child/children in schools are more likely to be a household with a negative cash flow. Especially, the expenditures on education and transportation were related with the likelihood of a household deficit.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제20권1호
• /
• pp.37-50
• /
• 2016

A large eddy simulation (LES) of a turbulent channel flow is performed by using the third order low-storage Runge-Kutta method in time and second order finite difference formulation in space with staggered grid at a Reynolds number, $Re_{\tau}=590$ based on the channel half width, ${\delta}$ and wall shear velocity, $u_{\tau}$. To reduce the calculation cost of LES, algebraic wall model (AWM) is applied to approximate the near-wall region. The computation is performed in a domain of $2{\pi}{\delta}{\times}2{\delta}{\times}{\pi}{\delta}$ with $32{\times}20{\times}32$ grid points. Standard Smagorinsky model is used for subgrid-scale (SGS) modeling. Essential turbulence statistics of the flow field are computed and compared with Direct Numerical Simulation (DNS) data and LES data using no wall model. Agreements as well as discrepancies are discussed. The flow structures in the computed flow field have also been discussed and compared with LES data using no wall model.

• 한국전산유체공학회지
• /
• 제16권4호
• /
• pp.28-38
• /
• 2011

Large eddy simulation(LES) of fully developed turbulent pipe flow has been performed to investigate the effect of Reynolds number on the flow field at $Re_{\tau}$=180, 395, 590 based on friction velocity and pipe radius. A dynamic subgrid-scale model for the turbulent subgrid-scale stresses was employed to close the governing equations. The mean flow properties, mean velocity profiles and turbulent intensities obtained from the present LES are in good agreement with the previous numerical and experimental results currently available. The Reynolds number effects were observed in the mean velocity profile, root-mean-square of velocity fluctuations, Reynolds shear stress and turbulent viscosity.