• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.8
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• pp.1009-1023
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• 1997

The breakup length of a liquid jet with flowrate, formed by releasing through a nozzle of circular cross-section into the atmosphere, was experimented and studied for 3 liquid nozzles of varying diameters. The experimental result was analyzed using the existing theoretical equation for predicting the breakup length. It was found that the breakup length of liquid jet depends on the velocity, and the breakup length increases with increasing of the liquid nozzle diameter. Also, the variation range of the breakup length for the same flowrate of liquid increased rapidly as velocity was increased for laminar flow, but in the turbulent flow region, it leveled off in the range of approximately 0.55-0.7 of the mean breakup length. Furthermore, when the longest smooth liquid jet was applied to the co-axial flow air blast atomizer, the effect of air flow on the flow pattern and breakup length was studied for 6 glass nozzles of different lengths and diameters. It was found that depending on the diameter of the mixing tube and liquid jet, it was possible to observe a wide range of flow patterns, such as liquid jet through flow, partial annular flow and annular flow. The liquid jet breakup length was more sensitive to the change in the length rather than the diameter of the mixing tube. As the length of the mixing tube shortens, the breakup length also shortens rapidly.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.8
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• pp.1121-1131
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• 1998

The present study is numerically investigated for the high-pressure effects on the vaporization process in the convection-dominating flow field. Numerical results agree well with the available experimental data. The fuel droplet vaporization characterization is parametrically studied for the wide range of the operating conditions encountered with the high-pressure combustion process of turbocharged diesel engines.

• Publications of The Korean Astronomical Society
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• v.8 no.1
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• pp.163-168
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• 1993

At intermediate mass transfer rates, accretion disks in binary star systems undergo a thermally-driven limit cycle instability. This instability leads to outburst episodes when the disk is bright and the flow through the disk is rapid separated by long intervals when the disk is dim and the flow through it is low. This intrinsic outburst mechanism can help to understand a wide range of astrophysical phenomena from dwarf novae to soft X -ray transients involving white dwarf, neutron star, and black holes. and to a deeper understanding of the mechanism of angular transport and viscosity in the accretion disk.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.12
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• pp.153-156
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• 1994

An in vitro steady flow experiment was performed in order to test the accuracy of velocity measurement obtained through a pulsed Doppler echocardiography. A flow phantom was designed for the use in a wide velocity range at a given flow rate. The results showed that the pulsed Doppler velocity measurement obtained in this flow phantom is accurate at low flow rates. However, ultrasound velocity measurement should be performed under a careful considerations of PRF and Doppler gain settings, especially at higher flow rates.

• International Journal of Fluid Machinery and Systems
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• v.5 no.1
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• pp.18-29
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• 2012

This paper deals with the CFD analysis of cavitating flow in the mixed-flow pump with the specific speed of 1.64 which suffers from a high level of noise and vibrations close to the optimal flow coefficient. The ANSYS CFX package has been used to solve URANS equations together with the Rayleigh-Plesset model and the SST-SAS turbulence model has been employed to capture highly unsteady phenomena inside the pump. The CFD analysis has provided a good picture of the cavitation structures inside the pump and their dynamics for a wide range of flow coefficients and NPSH values. Cavitation instabilities were detected at 70% of the optimal flow coefficient close to the NPSH3 value (NPSH3 is the net positive suction head required for the 3% drop of the total head of the pump).

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.30-34
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• 2001

In the present study, we studied the method of predicting the on-design and on-design point performance of axial flow fan with adjustable pitch blades. With the change of stagger angle of axial flow fan with adjustable pitch blade, flow rate and pressure can be changed. Because of this merit adjustable pitch fans are used in many industrial facility. When changing stagger angle or estimating the performance at a wide range of off-design condition, incidence angle changes greatly as the flow rate changes. Therefore, the deviation angle at the blade exit is estimated by the correlation considering the effects of blade design, incidence angle variation. In the loss model, we used known pressure loss model for blade boundary layer and wake, secondary flow, endwall boundary layer and tip leakage flow. The results of modified deviation angle model and experiment were compared for the usefulness of the modified model.

• Transactions of The Korea Fluid Power Systems Society
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• v.3 no.1
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• pp.15-19
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• 2006

In this study, a measurement method of leakage flow-rate for pneumatic driving apparatus is proposed. The existing measurement methods of leakage flow-rate of air need disassemble the test component. Therefore, there is no effective method to measure the leakage flow-rate while operating pneumatic driving apparatus. In this study, the leakage flow-rate is measure from the pressure change in an isothermal chamber that can realize isothermal conditions by stuffing steel wool into it. Therefore, wide range of flow-rate could be measured only from the pressure response and the leakage flow-rate can be measured during operating pneumatic driving apparatus. The effectiveness of the proposed method is proved by experimental results.

• Journal of Pharmaceutical Investigation
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• v.37 no.3
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• pp.137-148
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• 2007

Using a strain-controlled rheometer [Rheometrics Dynamic Analyzer (RDA II)], the steady shear flow properties of a semi-solid ointment base (vaseline) have been measured over a wide range of shear rates at temperature range of $25{\sim}60^{\circ}C$. In this article, the steady shear flow properties (shear stress, steady shear viscosity and yield stress) were reported from the experimentally obtained data and the effects of shear rate as well as temperature on these properties were discussed in detail. In addition, several inelastic-viscoplastic flow models including a yield stress parameter were employed to make a quantitative evaluation of the steady shear flow behavior, and then the applicability of these models was examined by calculating the various material parameters (yield stress, consistency index and flow behavior index). Main findings obtained from this study can be summarized as follows : (1) At temperature range lower than $40^{\circ}C$, vaseline is regarded as a viscoplastic material having a finite magnitude of yield stress and its flow behavior beyond a yield stress shows a shear-thinning (or pseudo-plastic) feature, indicating a decrease in steady shear viscosity as an increase in shear rate. At this temperature range, the flow curve of vaseline has two inflection points and the first inflection point occurring at relatively lower shear rate corresponds to a static yield stress. The static yield stress of vaseline is decreased with increasing temperature and takes place at a lower shear rate, due to a progressive breakdown of three dimensional network structure. (2) At temperature range higher than $45^{\circ}C$, vaseline becomes a viscous liquid with no yield stress and its flow character exhibits a Newtonian behavior, demonstrating a constant steady shear viscosity regardless of an increase in shear rate. With increasing temperature, vaseline begins to show a Newtonian behavior at a lower shear rate range, indicating that the microcrystalline structure is completely destroyed due to a synergic effect of high temperature and shear deformation. (3) Over a whole range of temperatures tested, the Herschel-Bulkley, Mizrahi-Berk, and Heinz-Casson models are all applicable and have an almostly equivalent ability to quantitatively describe the steady shear flow behavior of vaseline, whereas the Bingham, Casson,and Vocadlo models do not give a good ability.

• Journal of the Korean Society of Visualization
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• v.8 no.3
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• pp.12-21
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• 2010

Swirling flows are found in very wide range of applications, for examples, cyclone separators, spraying machines, heat exchangers and jet pumps, ect. Relatively, little work has been done on the swirl flow using flow visualization techniques. This study deals with many visualization techniques to study on swirling flow. These techniques are related to oil films methods, smoke, dye liquids, liquid crystal, stroboscope light, smoke wire, white light, naphthalene sublimation, LDV(lase doppler Velocimetry) and PIV(particle image velocimetry). The present work has handled single, annular, carved tube, swirl expansion and swirl wake using several visualization methods in the vertical and horizontal circular tube.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.2
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• pp.42-48
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• 1994

Turbocharging is one of the best methods to improve the performance of diesel engines, because of its merits,-power ratio, fuel consumption and exhaust emissions. Most of them in small and medium diesel engines have adopted the pulse turbocharging method with twin entry vaneless radial turbines to maximize the energy utility of exhaust gas. This method requires the high performance of turbine under unsteady flow, and also the matching between turbine and diesel engine is most important. However, it is difficult to match properly between them. Because the steady flow data are usually used for it. Accordingly, it is necessary to catch the characteristics of turbine performance correctly over the wide range of the operation conditions under unsteady flow. In this paper, the characteristics of turbine performance under unsteady flow are represented at varying conditions, such as inlet pressure amplitude, turbine speed and frequence.