• 한국분무공학회지
• /
• 제12권3호
• /
• pp.138-145
• /
• 2007

In the present work, the breakup mechanism of highly viscous epoxy paints discharged from a fan spray nozzle was examined experimentally. The paints tested were non-Newtonian fluids, composed of epoxy resin, solid particles and other additives. The paint spray discharged from the nozzle was visualized and recorded using a digital camera with back illumination. Due to presence of the solid particles, perforation of liquid sheet was observed in most cases, even at low-Reynolds number conditions (Re < 15,000) where the aerodynamic-wave breakup mode is used to be dominant for pure liquids. However, with the increase of the particle concentration, the sheet became longer and the thickness at breakup became thinner to some extent. This is because, with higher concentration of solid particles, the stabilizing effect by the viscosity increase predominates over the destabilizing effect by perforation.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1316-1321
• /
• 2004

An experimental study is performed on atomization characteristics and stable operating condition for injection of high viscous waste vegetable oil using effervescent atomizer with two aerator tubes. Consideration is given to the effects of ALR and liquid viscosity on the velocity and mean diameter of the injected droplet. It is found that (i) as ALR increases, the axial velocity of the droplet is increased, while half-velocity width and SMD are decreased regardless of the change in liquid viscosities, (ii) the rate of fine drop distribution occupied in the total spray field is increased with an increasing in ALR, and (iii) the effect of viscosity on atomization characteristics is minor.

• 대한조선학회논문집
• /
• 제47권1호
• /
• pp.38-46
• /
• 2010

This study aims at investigating the effect of the baffle height on the liquid sloshing in the three-dimensional (3D) rectangular tank. In order to simulate the 3D incompressible viscous two-phase flow in the 3D tank with partially filled liquid, the present study has adopted the volume of fluid (VOF) method based on the finite-volume method which has been well verified by comparing with the results of the relevant previous researches. The ratio of the baffle height ($h_B$) to filling level (h) has been changed in the range of $0{\leq}h_B/h{\leq}1.2$ to observe the effect on the impact loads on the side wall and free surface behavior. Generally, as baffle height increases, the impact pressure on the wall decreases and the deformation of free surface becomes weaker. However it seemed that a critical ratio of the baffle height existed to reveal the lowest impact pressure on the wall. Consequently, $h_B/h=0.8$ among $h_B/hs$ considered in the study showed the lowest impact pressure.

• 대한기계학회논문집
• /
• 제14권5호
• /
• pp.1330-1336
• /
• 1990

The factors to act on atomization of liquid fuel are viscosity, geometric shape of nozzle, atomizing pressure, etc. Most of high viscous liquid fuels show decrease in viscosity by raising the preheat temperature, but the viscosity of liquid fuel like CWM does not readily change with fuel temperature. As an experimental study to investigate the atomizing characteristics of CWM, CWM fuel is atomizing with a twin-fluid atomizer, and the effects of the geometric shape of spray nozzle on atomization are investigated by measuring the Sauter`s Mean Diameter (SMD) of CWM. The summarized results obtained in this study are as follows ; (1) As the ratio of the mass flows of atomizing air to that of fuel (W$_{a}$ /W$_{1}$) increases, 능 decreases when fuel temperature is constant. (2) At the ratio (t/d) 4 of thickness (t) of spray nozzle hole to the diameter (d) of the hole, there is the best atomization. And SMD decreases when t/d is between 1 to 4 and increases when t/d > 4.

• 한국분무공학회지
• /
• 제13권1호
• /
• pp.42-50
• /
• 2008

In the present work, atomization characteristics of shear-thinning liquid slurry discharging from fan spray nozzles were studied experimentally for spray painting applications. The effects of solid particle size and concentration on the properties (especially on the viscosity) of suspensions and mean drop size were examined by using model fluids. In the range of low particle concentration (below 3 wt%), the fluid viscosity was primarily determined by the particle size. On the other hand, in the range of high particle concentration (higher than 10 wt%), the agglomeration phenomenon and the oil absorption capability of solid particles played major roles in determining the fluid viscosity. In the high concentration region, which most of the paints belong to, the fluid became more viscous and the shear thinning behavior appeared more prominent as the particle concentration was increased. In this region, mean drop size(SMD) decreased more rapidly with the increase of the injection pressure. Also, SMD became larger with the higher particle concentration and the larger particle size.

• International Journal of Ocean System Engineering
• /
• 제2권1호
• /
• pp.32-36
• /
• 2012

This paper presents a comparison of potential and viscous computational codes for the water entry problem. A po-tential code was developed which adopted the boundary element method to solve the problem. A nonlinear free surface boundary condition was integrated to find new locations of free surface. The dynamic boundary condition was simplified by taking constant potential values for every time steps. The simplified dynamic boundary condition was applied in the new position of the free surface not at the mean level, which is the usual practice for linearized theory. The commercial code FLUENT was used to solve the water entry problem from the viscosity point of view. The movement of the air-liquid interface is traced by distribution of the volume fraction of water in a computational cell. The pressure coefficients were compared with each other, while experimental results published by other researchers were also examined. The characteristics of each method were discussed to clarify merits and limitations when they were applied to the water entry problems.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2009년도 추계학술대회 논문집
• /
• pp.842-849
• /
• 2009

The objective of this study is to investigate design parameters of a tuned liquid column damper(TLCD), which is affected by various excitation amplitudes, through shaking table test. Design parameters of a TLCD are examined based on the equivalent tuned mass damper(TMD) model of a TLCD, in which the nonlinear damping of a TLCD is transposed to equivalent viscous damping. Shaking table test is carried out for a TLCD specimen subjected to harmonic waves with various amplitudes. Transfer functions are ratios of liquid displacement of TLCD and control force produced by a TLCD, respectively, with respect to the acceleration excited by a shaking table. They are derived based on the equivalent TMD model of a TLCD. Then, the variation of design parameters according to the excitation amplitude is examined by comparing analytical transfer functions with experimental ones. Finally, the dissipation energy due to the damping of a TLCD, which is experimentally observed from the shaking table test, is examined according to the excitation amplitude. Comparisons between test results and analytical transfer functions showed that natural frequencies of TLCD and the ratio of the liquid mass in a horizontal column to the total liquid mass does not depend on the excitation amplitude, while the damping ratio of a TLCD increases with larger excitation amplitudes.

• 한국소음진동공학회논문집
• /
• 제19권11호
• /
• pp.1167-1176
• /
• 2009

The objective of this study is to investigate design parameters of a tuned liquid column damper(TLCD), which is affected by various excitation amplitude, through shaking table test. Design parameters of a TLCD are examined based on the equivalent tuned mass damper(TMD) model of a TLCD, in which the nonlinear damping of a TLCD is transposed to equivalent viscous damping. Shaking table test is carried out for a TLCD specimen subjected to harmonic waves with various amplitude. Transfer functions are ratios of liquid displacement of TLCD and control force produced by a TLCD, respectively, with respect to the acceleration excited by a shaking table. They are derived based on the equivalent TMD model of a TLCD. Then, the variation of design parameters according to the excitation amplitude is examined by comparing analytical transfer functions with experimental ones. Finally, the dissipation energy due to the damping of a TLCD, which is experimentally observed from the shaking table test, is examined according to the excitation amplitude. Comparisons between test results and analytical transfer functions showed that natural frequencies of TLCD and the ratio of the liquid mass in a horizontal column to the total liquid mass do not depend on the excitation amplitude, while the damping ratio of a TLCD increases with larger excitation amplitude.

• 대한기계학회논문집B
• /
• 제39권1호
• /
• pp.97-107
• /
• 2015

2 상 유동장에 놓인 열 교환기 튜브에 작용하는 점성 감쇠비와 압착막 감쇠비를 예측하기 위한 해석 모델이 개발되었다. 열 교환기 튜브에 작용하는 유동유발진동을 해석하기 위하여 감쇠에 대한 정보가 요구된다. 열 교환기 튜브에서 가장 중요한 에너지 소산 기구는 튜브와 지지물과 같은 구조물과 액체 사이의 동적 작용에 연계되어 있다. 본 모델은 1997 년 발표된 근사모델에 근거하고 부가질량계수를 고려하여 개발되었다. 어림적 해석모델은 동심환 내에서 진동하는 내부 실린더에 작용하는 수력학적 힘을 계산하기 위하여 개발되었다. 점성력을 포함한 수동력은 높고 혹은 낮은 진동 레이놀드 수에 따라 개발된 두 가지 모델을 사용하여 각각 계산할 수 있다. 관군과 지지대에서의 상당 직경과 침투깊이는 관군에 작용하는 점성 감쇠력과 지지대에서의 압착막 감쇠력을 각각 계산하는데 매우 중요한 변수이다. 2 상 유동의 기공률을 계산하기 위하여 균질모델이 사용되었다. 본 모델을 검증하기 위하여, 모델의 해석결과는 기존의 이론으로 구한 결과와 비교하였다. 본 모델을 사용하여 점성 감쇠비와 압착막 감쇠비를 어림적으로 구할 수 있음을 보였다.

• KSBB Journal
• /
• 제7권1호
• /
• pp.59-65
• /
• 1992

외부 순환식 공기리프트 반응기에서 기상유속과 액상의 점도를 변수로 하여 기체체류량과 액체의 순환시간, 혼합시간, 순환속도 및 축방향분산계수를 측정하여 다음과 같은 결론을 얻었다. 1. 기체체류량은 기체유속이 증가함에 따라 증가 하였으며, 점도가 증가함에 따라서는 약간 감소하는 경향을 보였다. 또 기체유속이 증가함에 따라 상승관에서는 기체체류량의 증가율이 감소한 반면 하강관에서는 증가하였다. 2. 기체유속이 증가함에 따라 순환시간 및 혼합시간은 초기에 급격히 짧아지다가 거의 일정한 값을 나타내었으며, 액체의 점도가 증가함에 따라 순환기산과 혼합시간은 모두 증가하였다. 3. 순환 액체의 속도는 기체의 속도에 따라 초기에 급격히 증가하나 기체속도가 약 5cm/sec이상이 되면 그 증가율이 매우 둔화되었으며, 점도가 증가함에 따라 약간 감소함을 알 수 있었다. 또한 압력수지식으로 예측한 이론값과 실험값은 낮은 기체유속 영역에서는 잘 일치하였으나 기체유속이 증가함에 따라 실험값이 이론값보다 작은 값을 나타내었다. 4. 기체유속이 증가함에 따라 Bodenstein number는 감소하였고, 축방향분산계수는 증가하였으며, 점도가 증가함에 따라 약간 감소하는 경향을 보였다. 본 실험범위에서 분산이 많이 일어나mixed folw에 근접함을 알 수 있었다.