• 한국수자원학회논문집
• /
• 제30권3호
• /
• pp.201-210
• /
• 1997

$textsc{k}$-$\varepsilon$난류모델을 이용한 개수로 급축소부 흐름의 해석을 위한 수치모형을 개발하였고, 그 수치실험결과는 실험결과와 잘 일치하였다. 이는 난류모델에 의한 적절한 난류 와점성계수의 산정이라 생각된다. 유함수 및 유속분포의 분석을 통한 축소부 통과후 급변화 흐름의 수리특성을 분석하였고, 또한 난류 와점성계수의 분포를 분석하였다. 따라서 천수방정식의 점성항에 경험적인 유효점성계수의 도입보다는 흐름의 양상과 장소에 따라서 변화하는 난류와점성계수의 산정에 의한 급변화흐름의 해석이 필요하다.

• Tribology and Lubricants
• /
• 제14권1호
• /
• pp.85-93
• /
• 1998

The Bair & Winer's limiting shear stress rheological model is incorporated into the Reynolds equation to successfully predict the traction and film thickness for an isothermal line contact using the primary rheological properties. The modified WLF viscosity model and Barus viscosity model are also adapted for the realistic prediction of EHD tractional behavior. The influences of the limiting shear stress and slide-roll ratio on the pressure spike, film thickness, distribution of shear stress and nonlinear variation of traction are examined. A good agreement between the disc machine experiments and numerical traction prediction has been established. The film thickness due to non-Newtonian effects does not deviate significantly from the fdm thicknesss with Newtonian lubricant.

• 대한기계학회논문집B
• /
• 제27권9호
• /
• pp.1327-1334
• /
• 2003

Flow characteristics of the fluid laden with many particles in the two-dimensional channel are investigated using the Navier-Stokes equations coupled with the equation of motion of particles by direct numerical simulation. A four-step fractional step method with Crank-Nicolson scheme and ALE technique is used for P2P1 mixed finite element method. The motion and distribution of particles in the fluid is virtually described as a result of direct numerical simulation and the increase of viscosity is compared with theoretical equations. The effect of channel height on the relative viscosity and the tubular pinch effect are discussed.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.786-791
• /
• 2003

We have studied on the main causes of pressure drop in the paint hose under the spraying with airless spray pump and suggest calculation method for selecting the optimum pressure drop during the spraying. Among many factors contributing the pressure drop during the airless spraying procedure of paint, some of the key factors and the correct method for checking pressure loss between airless pump and spray gun are addressed. We have developed pressure loss calculation method which depending on hose length and diameter, viscosity and flow rate in the painting hose during the spraying. also we have developed calculation equation for the expected spray tip flow rate which depending on pressure and specific gravity and tip size.

• 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.

• 설비공학논문집
• /
• 제13권7호
• /
• pp.653-665
• /
• 2001

The characteristics of the pulsating flow in a hydraulic pipe have been investigated. It is necessary to study the power control of the power transmission system in the landing gear system of aircraft and the design of robots. In this system, the power transmission pipeline is composed of a hydraulic system, and the operating flow is unsteady flow. The wave equation varying with frequency is analyzed in order to investigate the characteristics of unsteady flow in such a pipe. This wave equation involves the propagation coefficient in terns of frequency and viscosity. The theoretical result of this wave equation are compared with experimental result. Each wave equation, varying with the propagation coefficient, is analyzed theoretically. then, a sinusoidal wave generator is built in order to make better sinusoidal waves, and a rectifier is built to eliminate the noise from the hydraulic pump. The theoretical results of the wave equation in the flow of viscous fluid agree well with experimental results.

• International Journal of Aeronautical and Space Sciences
• /
• 제9권2호
• /
• pp.34-40
• /
• 2008

The aeroelastic analyses for several wing models were performed using the transonic small-disturbance (TSD) equation, which is very efficient, to consider the aerodynamic nonlinearities in the transonic region. For more accurate aerodynamic analysis of airfoil and wing models with shock waves, the viscous equations based on the Green's lag-entrainment equation of boundary-layer effects were coupled with the TSD equation in the transonic region. Finally the aeroelastic characteristics of wing models were investigated through comparisons of the aeroelastic analysis results for wing models considering the change of a thickness of the airfoil section. Moreover, the results of the aeroelastic analysis using the coupled TSD equation with the viscous equations were compared with those using the TSD equation for several wing models.

• 한국해안·해양공학회논문집
• /
• 제27권6호
• /
• pp.406-418
• /
• 2015

기존 FUNWAVE-TVD 버전 2.1 모형을 수정한 본 모형의 검증을 위해 고립파 실험, Vincent and Briggs(1989)의 비쇄파 및 쇄파 실험, Luth et al. (1994)의 수리실험을 수행하였다. 쇄파 실험의 경우 기존 결과와 비교하기 위하여 eddy viscosity를 이용한 쇄파 방법도 포함하였다. Eddy viscosity 쇄파 방법을 이용하여 Vincent and Briggs(1989)의 쇄파 실험에 적용한 결과 수정된 모형에서는 수중천퇴 중심의 y축을 기준으로 파랑류(wave-induced current)의 대칭성이 유지되었으나 FUNWAVE-TVD 버전 2.1 모형에서는 대칭성이 유지되지 않았다. 또한 eddy viscosity 쇄파 방법을 이용한 경우가 천수방정식으로 전환하여 쇄파를 모의하는 방법보다 관측치에 더 가깝다. 그리고 FUNWAVE-TVD 버전 2.1 모형에 사용한 기법들과 비교하기 위하여 Erduran et al.(2005)이 제시한 4차 정확도의 MUSCL-TVD 기법과 minmod limiter를 이용한 3차 정확도의 기법을 적용하여 고립파의 전파 양상을 비교 검토하였다.

• 대한화학회지
• /
• 제54권1호
• /
• pp.71-76
• /
• 2010

298.15~318.15 K 온도에서 디지탈 진동 U-tube densimeter 와 Ubbelohde 모세관 점성계을 사용하여 2-브로모프로판/메탄올 이성분 혼합물의 밀도와 점성도를 측정하였다. 온도와 농도에 대한 밀도와 점성도 상호 의존 관계를 조사하였다. 이성분 혼합물의 여분 몰부피와 여분 점성도를 실험으로 얻어진 밀도와 점성돌로부터 계산하여 구하였다. 모델이 실험치와 잘부합됨을 발견하였다.

• Journal of Biosystems Engineering
• /
• 제21권2호
• /
• pp.198-207
• /
• 1996

To measure the moisture content, protein and viscosity of brown and milled rice with Near Infrared Reflectance(NIR) analyzer, the comparison and analysis of the data from the chemical analysis and NIR analyzer were conducted. The purpose of this study is to find out the fundamental data required for the prediction of rice qualify and taste rank, and to develop a measuring method of constituents and physical characteristics of domestic rice with NIR analyzer. The important results can be summarized as follows. 1. The $r^2$ and SEC of moisture calibration from brown rice powder were 0.87 and 0.09 respectively, those of milled rice powder were 0.95 and 0.08 respectively. 2. The $r^2$ and SEC of protein calibration from brown rice powder were 0.83 and 0.20 respectively, those of milled rice powder were 0.86 and 0.20 respectively. 3. The $r^2$ and SEC of viscosity calibration from brown rice powder were 0.36 and 15.50 respectively, those of milled rice powder were 0.55 and 12.98 respectively. Further study is required to develop better prediction model for viscosity. It is necessary the continuous study including wavelength selection, because $r^2$ is small for practical use. 4. The regression equation for one rice variety was nearly coincident with other. Therefore, it is required that the prediction model should be developed for the all rice samples.