• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.81-92
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• 2018

For a marine bridge foundation construction, a large-circular-steel-pipe has been proposed for supporting vertical load and preventing water infiltration. However, a ship collision can adversely affect the structural stability. This paper presents a fundamental study on dynamic responses of the large-circular-steel-pipe by an impact load. In laboratory experiments, small-scaled steel pipe is installed in a soil tank. The soil height and water level are set to 23 cm and 25~70 cm, respectively. The upper part of the steel pipe is impacted using a hammer to simulate the ship collision. The dynamic responses are measured using accelerometers and strain gauges. Experimental results show that the strain decreases as the measured location is lowered. The higher frequency components appear in the impact load condition compared to the microtremor condition. However, the higher frequency components measured at the strain gauge located below the water level do not appear. For the accelerometer signal, the maximum frequency under the impact load is higher than that of the microtremor. The maximum frequency decreases as water level increases but it is larger than the maximum frequency of the microtremor. This study shows that strain gauge and accelerometer can be useful for evaluating the dynamic responses of large-circular-steel-pipes.

• Journal of the Korean Society for Advanced Composite Structures
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• v.1 no.1
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• pp.27-33
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• 2010

Static analyses and buckling analyses were carried out for buried GFRP pipes by using finite element method. Vehicle loads, vertical and lateral soil pressures were considered as external loads, and supplying water pressure was considered as an internal load. Nine types of the factory-manufactured GFRP pipes were analyzed. Their maximum stresses and displacements were compared with the limit displacements and ultimate stress. Additionally, stress analysis on an enhanced flange, which was designed to reduce stress concentration, was performed. A cantilever analysis was carried out to know the maximum stress on the neck of the flange, which is the critical part. And a static analysis was carried for the buried flange. The test results showed that GFRP pipes were safe and stable against the external loads. And they showed that the enhanced flange decreased about 35% of the stress concentration.

• The KSFM Journal of Fluid Machinery
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• v.5 no.1 s.14
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• pp.7-12
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• 2002

As the first step to investigate the fundamental mechanism of a dispersed two-phase flow, we studied the detailed interactions between bubble or particle motion and flow around it. Experiments were carried out with a rising bubble or particle in stagnant water in a vertical pipe. Particles with different densities, and/or different shapes were used for comparison with a bubble. We adopted 3D-PTV (Three-Dimensional Particle Tracking Velocimetry) for measuring the bubble or particle motions, and PIV (Particle Image Velocimetry) for measuring the water flow simultaneously (Hybrid PIV). The experimental results showed that the oblate spheroidal solid particle rose along the longer axis direction at the point that the inclination of the longer axis reached the maximum, and the inclination direction changed after moving. The bubble moved to the direction that the spheroid's projected width grew up to the largest, and the minor axis of the oblate spheroidal body of the bubble was parallel to the moving direction. The trajectory of the center of the particle/bubble which was measured with 3D-PTV, was marked on the section (x-y) of the pipe. It exhibited the pattern of the particle/bubble motion.

• Earthquakes and Structures
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• v.18 no.3
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• pp.297-312
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• 2020

The KiK-net by NIED is a vertical array measurement system. In the database of KiK-net, singular pulse waves were observed in the seismic record at the borehole of TTRH02 during the mainshock (the magnitude of Japan Meteorological Agency (M_J) 7.3, M_W 6.8) and aftershock (M_j 4.2) of Tottori-ken Seibu earthquake in 2000. Singular pulse waves were also detected in the seismic records at the borehole of IWTH25 during the Iwate-Miyagi Nairiku earthquake in 2008 (M_J 7.2, M_W 6.9). These pulse waves are investigated by using the wave shape analysis methods, e.g., the non-stationary Fourier spectra and the double integrated displacement profiles. Two types of vibration modes are discriminated as the occurrence mechanism of the singular pulse waves. One corresponds to the reversal points in the displacement profile with the amplitude from 10^-4 m to 10^-1 m, which is mainly related to the fault activity and the amplification pass including the mechanical amplification (collision) of the seismograph in the casing pipe. The other is the cyclic pulse waves in the interval of reversal points, which is estimated as the backlash of the seismograph itself with the amplitude from 10^-5 m to 10^-4 m.

• Journal of ILASS-Korea
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• v.16 no.2
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• pp.82-89
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• 2011

When pipe components made of carbon steel in nuclear, fossil, and industry plants are exposed to flowing fluid, wall thinning caused by FAC(flow accelerated corrosion) can be generated and eventually ruptured at the position of pressure boundary. The aim of this study is to identify the locations at which local wall thinning occurs and to determine the turbulence coefficient related to local wall thinning. Experiment and numerical analyses for the tee sections of down scaled piping components were performed and the results were compared. In particular, flow visualization experiment which was used alkali metallic salt was performed to find actual location of local wall thinning inside tee components. In order to determine the relationship between turbulence coefficients and local wall thinning, numerical analyses were performed for tee components in the main feedwater systems. The turbulence coefficients based on the numerical analyses were compared with the local wall thinning based on the measured data. From the comparison of the results, the vertical flow velocity component(Vr) flowing to the wall after separating in the wall due to the geometrical configuration and colliding with the wall directly at an angle of some degree was analogous to the configuration of local wall thinning.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.662-667
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• 2009

The research are performed to check the characteristics of the ice slurry transport system for the district cooling. The system are installed at the 1st floored building which is as large as the $1204\;m^2$ ($86\;m{\times}14\;m$), and the pumping power and branching characteristics are measured by transporting of the ice slurry. The ice slurry transporting pipe is as long as 200 m. For the same cooling load, the higher IPF is, the lower the transporting flow rate and the pumping power are. But when the IPF is higher than 15%, no less decrease of the pumping power does happen. For the branching characteristics, through the branch pipe where the flow resistance is higher, the higher IPF is measured. A little higher IPF is measured at the thermal expansion branch.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1315-1320
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• 2008

An experimental study was carried out to study the solid-liquid mixture upward flow in a vertical and inclined annulus with rotating inner cylinder. Lift forces acting on a fluidized particle plays a central role in many importance applications, such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs, sediment transport and cleaning of particles from surfaces, etc. Field measurements have revealed that the pressure drop over a borehole during drilling of a slim oil well or a well with a long reach can depend significantly on the rotation speed of the drill pipe. An accurate prediction of the annular frictional pressure drop is therefore important for conditions where the annular clearance is small. Effect of annulus inclination and drill pipe rotation on the carrying capacity of drilling fluid, particle rising velocity, and pressure drop in the slim hole annulus have been measured for fully developed flows of water and of aqueous solutions.

• Journal of the Korean Solar Energy Society
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• v.33 no.1
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• pp.57-65
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• 2013

The temperatures with the ground depth, the positions of circulation water in ground heat exchanger were measured and thermal diffusion characteristics with the distances of the direction normal to the borehole was analysed. The deeper the depth of ground, the less the influences of outdoor temperature, but below 10m of ground, there was no influences of ground temperature. When the depth of trench pipe was below the depth of 2m, there was no influence. In the ground of 10m when the distances between the pipe and the other places were above 0.5m, the variations of temperature were less than $1.6^{\circ}C$ and above 2.5m they were less than $0.1^{\circ}C$. When the distances of bore hole were above 5m, there were no. influences of the nearest ground heat exchanger.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.800-806
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• 2019

This paper presents a laboratory experiment on data acquisition technique that applied to the gamma radiation scanning coupled with computed tomography (CT) technique for inspection of broken nozzle inside the vertical vessel. The acquisition technique was developed to inspect a large diameter vessel when suspicious problem location is not easily accessed. This technique allows the installation of gamma radiation source (Cesium 137, Cs-137), and detectors (Sodium Iodine. NaI(Tl)) from the accessible location to the required location and performs the scanning by designed pattern. To demonstrate the designed technique, top opened tank which installed with six cut steel pipes diameter of 76.2 mm (3") at a certain position was selected. They were assumed to be a gas riser pipes inside the vessel. Three studied cases were performed, (a) projection of well installed six pipes, (b) projection of one out of six broken pipe and (c) one of nozzle was assumed to be failure and fell down until one out of six pipes was broken and obstructed by nozzle. Results clearly indicated the capability of developed technique to distinguish between normal situation case and abnormal situation cases.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.1
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• pp.48-56
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• 2021

In this study, the heat transfer process around the finned channel tubes is numerically examined. Serially arranged tubes of an evaporator were used for heat exchange. The numerical analysis results confirmed that the vortex generated at the rear of the channel pipe was caused by the fin. Furthermore, it was also confirmed that the temperature difference was large between the inlet and outlet ends of the fin. The temperature of the location where the fin was attached to the channel pipe was found to be close to the surface temperature of the channel wall. However, the temperature rose rapidly closer to the ambient air temperature of 350 K towards the fin end, located at a distance of 0.035 m; it was found to have a significant influence on the heat transfer around the fin-attached channel tube. The wider the vertical flow path, the lower the total heat transfer coefficient. However, the overall heat transfer coefficient increased as the horizontal flow path narrowed. The increment is attributed to an increase in the heat transfer amount due to increased heat transfer surface.