• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.4
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• pp.1458-1471
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• 1996

The present study is concerned with the heat transfer enhancement associated with a symmetrical or asymmetrical horseshoe vortex in front of and around the circular cylinder centered between the side walls of a wind tunnel. The static pressure measurements and the flow visualization in front of and around cylinders have been performed to determine the existence of horseshoe vortex. The hue-capturing method using the thermochromatic liquid crystals with great spatial resolution was used to obtain the local information of the endwall heat transfer coefficients. In case of one cylinder, the convective heat transfer coefficients of the region where the horseshoe vortex exists are larger than those of any other region. In case of two cylinders with tandem arrangement, the heat transfer rate of gap spacing (d/D= 1.5) is higher than that of gap spacings (d/D=2.0 or 2.5).

• New & Renewable Energy
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• v.9 no.4
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• pp.32-39
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• 2013

A 2-loop waste heat recovery system with Rankine steam cycles for the improvement of fuel efficiency of gasoline vehicles has been investigated. A high temperature loop is used to recover waste heat from exhaust gas and a low temperature loop is used to recover waste heat from cold engine coolant. This paper has dealt with a layout of low temperature loop system, the review of the velocity contours through numerical analysis. According to the result of analysis, the designed heat exchanger. And comparing with flow analysis results, LT Boiler is safe to operation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.3
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• pp.263-270
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• 2016

This study is aimed to design the mechanical gascyclone precipitator with an outstanding collection efficiency as one of ways to reduce exhaust gas of small-scale vessels. It estimated fine particles generated from diesel engines which has become one of the biggest environmental issues currently. Specifically, it quantitatively analyzed the flowing process from the cyclone gas exit; a duct via part to the collecting part of Cylindrical lower using DPIV (Digital Particle Image Velocimetry). Since the gas inlet height part became wider the previous theoretical dimensions, internal fluid characteristics of cyclone where the speed of internal swirl had been slow were investigated by temporary streamline of fine particles at $14-20{\mu}m$. The results showed that collecting efficiency was three times higher than the conical type utilized previously. In addition, this study supplemented imprecision problems from the previous theoretical equation and CFD interpretation with an experimental method. It also provided a basic data to design the cyclone precipitator by size of diesel engines for vessels.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.254-259
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• 2001

There are advantages in the installation of dual subsea pipelines over two separate single lines. In many case it can reduce the cost for trench, back-filling and installation. However the installation of dual pipelines often requires technical challenges. Dual Pipelines should be placed to be stable to external loading not only during the installation but also in the design life. Dual pipelines in trench can reduce the influence of external forces. To investigate applied forces as slope changes, number of experiments are conducted with PIV (Particle Image Velocimetry) in a circulating water channel. Numerical approaches are also made to compare with experimental results. The velocity fields around dual pipelines in trench are investigated and analysed. Comparison of both results show similar pattern of flow around dual pipelines. it is proved that the trench slope affects the pipeline stability significantly. The results can be applied in the stability design of dual pipelines in trench section. The complex flow patterns can be referenced effectively linked in the understanding of fluid around circular bodies in trench.

• Aerospace Engineering and Technology
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• v.1 no.2
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• pp.51-56
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• 2002

Satellite propulsion system is employed for orbit transfer, orbit correction, and attitude control. The monopropellant feeding system in the low-earth-orbit satellite blowdowns fuel to the thrust chamber. The thrust produced by the thruster depends on fuel amount flowed into the combustion chamber. If the thruster valve be given on-off signal from on-board commander in the satellite, valve will be opened or closed. When the thrusters fire fuel flows through opened thruster valve, instantaneous stoppage of flow in according to valve actuation produces transient pressure due to pressure wave. This paper describes transient pressure predictions of the KOMPSAT-2 propulsion system resulting from latching valve and thrust control valve operations. The time-dependent set of the fluid mass and momentum equations are calculated by MOC.

• Aerospace Engineering and Technology
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• v.1 no.2
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• pp.1-10
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• 2002

Flow computations around forward sweep wing small aircraft have been conducted in this study. The main-wing of the forward-wing small aircraft is composed of two planforms: the inboard wing section with backward sweep angle which is known as strake and the outboard wing section with forward sweep angle. The geometrical discontinuity or kink generated by the combination of these two different planforms requires detailed flow analysis around wing. Four different solvers were used to calculate aerodynamic data and the accuracy of each method is examined. For the convenience of grid generation over the aircraft geometry, the overset grid method was applied. Through this calculation, the basic aerodynamic data of the forward-wing aircraft were provided and the aerodynamic characteristics of the wing is expounded.

• Journal of Ocean Engineering and Technology
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• v.31 no.4
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• pp.281-287
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• 2017

In the case of fixed offshore wind turbines, scouring phenomena have been reported around sub-structures as a result of currents, which seriously damage the structural stability. A parametric study of the various sub-structures of a fixed offshore wind turbine was performed to investigate their effects on the scouring phenomena. For a suction bucket foundation and monopile, the effects of the stick-up heights and water depth were studied, respectively. The open source libraries, called OpenFOAM, were used to simulate a violent flow around a foundation. The numerical methods were selected based on a two-dimensional analysis of a suction bucket. Based on the results for various stick-up heights, a larger scouring region was observed with an increase in the stick-up height because of the down-wash flow around a foundation. Based on the results for various monopile water depths, the water depth had an insignificant effect on the scouring.

• Journal of Veterinary Clinics
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• v.34 no.2
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• pp.90-93
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• 2017

A nine-month-old intact female Maltese dog (body weight: 1.5 kg) presented with frequent syncopal episodes (1-2/day), exercise intolerance, and dyspnea. Cardiomegaly with marked dilation of right and left atria along with ascites was indicated on radiography. Tricuspid regurgitant jets (4.36 m/s), pulmonary regurgitant jets (3.4 m/s), left-to-right shunting flow at the ductus arteriosus, and an atrial septal defect were observed on echocardiography. A bubble study with agitated saline found right-to-left shunting at the interatrial septum. Based on diagnostic studies, the dog was diagnosed with right-to-left atrial septum defect (ASD) compounded with patent ductus arteriosus (PDA). The treatment was directed to reduce the pulmonary hypertension, improve cardiac performance, and lower fluid retention. Despite medical treatment for 2 months, the dog died of sudden cardiac arrest. Herein, we describe a very rare case of right-to-left ASD compounded with PDA.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.4
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• pp.43-48
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• 2013

A study is analyzed on the adverse pressure gradient and the transient regime of supersonic diffuser with Computational Fluid Dynamic. The flow field of supersonic diffuser is calculated using Axisymmetric two-dimensional Navier-Stokes equation with $k-{\epsilon}$ turbulence model. The transient simulation is compared in terms of mach number and static temperature of vacuum chamber according to pressure variation of rocket engine combustion chamber. Combustion gas flow into the vacuum chamber during operation of the supersonic diffuser. According to this phenomenon, the pressure and the temperature rise in the vacuum chamber were observed. Thus, the protection system will be necessary to prevent the pressure and temperature rise in the transition process during operation of the subsonic diffuser.

• Wind and Structures
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• v.39 no.1
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• pp.71-84
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• 2024

The wind-resistant performance of bridges is generally evaluated based on the strip assumption. For the arch rib of arch bridges, the situation is different due to the curve axis and the variable cross-sectional size. In the construction stage, the arch rib supported by a cable system exhibits flexible dynamic characteristics, and the wind-resistant performance attracts specially attention. To evaluate the wind-induced vibration of an arch rib with the maximum cantilever state, the finite element model was established to compute the structural dynamic characteristics. Then, a three-dimensional (3D) fluid-solid coupling analysis method was realized. After verifying the reliability of the method based on a square column, the wind-induced vibration of the arch rib was computed. The vortex-induced vibration (VIV) performance of the arch rib was focused and the flow field characteristics were discussed to explain the VIV phenomenon. The results show that the arch rib with the maximum cantilever state had the possibility of VIV at high wind speeds but the galloping was not observed. The lock-in wind speeds were larger than the results based on the strip assumption. Due to the vibration of arch rib, the frequency of shedding vortices along the arch axis trended to be uniform.