• International Journal of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.93-102
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• 2021

In this research, we present a natural lighting system with transmission distance of 30m and lighting efficiency of 35% (30m standard) for operating hours of 7h/day (based on clear sky). The system is composed of parabolic reflective mirror and modified light pipe that can secure more than 88% of light concentration efficiency. The light loss rate of newly designed light pipe transmission system is demonstrated to 0.8 %/m in the straight-line part and 2%/m in the curved part. Modified light pipe daylighting system shows better performance over fiber optic daylighting system in terms of transmission distance (1.5 times longer) and illuminance (3.05 times higher).

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.16 no.1
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• pp.65-84
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• 2012

We present an application of the variational multiscale methodology to the computation of concentric annular pipe flow. Isogeometric analysis is utilized for higher order approximation of the solution using Non-Uniform Rational B-Splines (NURBS) functions. The ability of NURBS to exactly represent curved geometries makes NURBS-based isogeometric analysis attractive for the application to the flow through the curved channel.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.288-294
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• 1996

In this paper, Chaotic motions of a curved pipe conveying oscillatory flow are theoretically investigated. The nonlinear partial differential equation of motion is derived by Newton's method. The transformed nonlinear ordinary differential equation is a type of Hill's equation, which have the parametric and external excitation. Bifurcation curves of chaotic motion of the piping systems are obtained by applying Melnikov's method. Poincare maps numerically demonstrate theoretical results and show transverse homoclinic orbit of the chaotic motion.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.501-517
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• 2020

Three-dimensional numerical simulations were performed to study the effects of flow direction and flow velocity on the flow regime behind a curved pipe represented by a curved circular cylinder. The cylinder is based on a previous study and consists of a quarter segment of a ring and a horizontal part at the end of the ring. The cylinder was rotated in the computational domain to examine five incident flow angles of 0-180° with 45° intervals at Reynolds numbers of 100 and 500. The detailed wake topologies represented by λ2 criterion were captured using a Large Eddy Simulation (LES). The curved cylinder leads to different flow regimes along the span, which shows the three-dimensionality of the wake field. At a Reynolds number of 100, the shedding was suppressed after flow angle of 135°, and oblique flow was observed at 90°. At a Reynolds number of 500, vortex dislocation was detected at 90° and 135°. These observations are in good agreement with the three-dimensionality of the wake field that arose due to the curved shape.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1031-1038
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• 2001

In order to verify the analytical methods predicting failure behavior of cracked piping, full-scale pipe tests are crucial in nuclear power plant piping. For this reason, series of international test programs have been conducted. However, full-scale pipe tests require expensive testing equipment and long period of testing time. The objective of this paper is to develop a test system which can economically simulate the full-scale pipe test regarding the integrity evaluation. This system provides the failure behavior of cracked pipe by testing a wide-plate specimen. The system provides the failure behavior of cracked pipe by testing a wide-plate specimen. The system was developed for the integrity evaluation of nuclear piping based on the methodology of hardware-in-the-loop (HiL) simulation. Using this simulator, the piping integrity can be evaluated based on the elastic-plastic behavior of full-scale pipe, and the high cost full-scale pipe test may be replaced with this economical system.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.317-322
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• 2001

This study depicts an experimental work of the impulsive wave discharged from the open end of several kinds of right-angle bend pipes, which are attached to the open end of a simple shock tube. The weak normal shock wave with its magnitude of Mach number from 1.03 to 1.20 is employed to obtain the impulsive wave propagating outside the open end of the bend pipes. The experimental data of the magnitude of the impulsive wave and its propagation directivity are analyzed to characterize the impulsive waves discharged from the right-angle bend pipes and compared with those from a straight pipe. The results obtained show that a right-angle miter bend considerably reduces the magnitude of the impulsive wave and its directivity toward to the pipe axis, compared with the straight pipe. It is believed that the right angle miter bend pipe can playa role of passive control against the impulsive wave.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.386-391
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• 2001

In this paper, the vibration characteristics of IHTS(Intermediate Heat Transfer System) piping system of LMR(Liquid Metal Reactor) conveying hot liquid sodium are investigated to eliminate the pipe supports for economic reasons. To do this, a 3-dimensional straight pipe element and a curved pipe element conveying fluid are formulated using the dynamic stiffness method of the wave approach and coded to be applied to any complex piping system. Using this method, the dynamic characteristics including the natural frequency, the frequency response functions, and the dynamic instability due to the pipe internal flow velocity are analyzed. As one of the design parameters, the vibration energy flow is also analyzed to investigate the disturbance transmission paths for the resonant excitation and the non-resonant excitations.

• Journal of the Korean Institute of Gas
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• v.6 no.1 s.17
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• pp.1-9
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• 2002

This paper presents simple models for flow and the PIG dynamics when it passes through a $90^{\circ}$ curved section of pipeline. The simulation has been done with two different operational boundary conditions. The solution fur non-linear hyperbolic partial equations for flow is given by using MOC. The Runge-Kuta method is used to solve the initial condition equation fur flow and the PIG dynamics equation. The simulation results show that the proposed model and solution can be used fur estimating the PIG dynamics when the pig runs in the pipeline including curved section. In this paper, dynamic modeling and its analysis for the PIG flow through $90^{\circ}$ curved pipe with compressible and unsteady flow are studied. The PIG dynamics model is derived by using Lagrange equation under assumption that it passes through 3 different sections in the curved pipeline such that it moves into, inside and out of the curved section. The downstream and up stream flow dynamics including the curved sections are solved using MOC. The effectiveness of the derived mathematical models is estimated by simulation results fur a low pressure natural gas pipeline including downward and upward curved sections. The simulation results show that the proposed model and solution can be used for estimating the PIG dynamics when we pig the pipeline including curved section.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.227-243
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• 2003

To find the structural characteristics of non-slip device in connecting method B between steel pipe pile and concrete footing, compression and uplift test was performed for full sized specimens not having non-slip device, those having non-slip device with two curved steel plate bars welded inside the steel pipe pile(standard method), and those having non-slip device with serveral curved steel plate bars bolted inside the steel pipe pile(new method). As a result, specimens not having non-slip device had chemical debonding failure at 15.6tonf of peak uplift load and 27.57tonf of peak compression load. And the standard method and the new method showed about 8.9 times of peak uplift load and 6.2 times of peak compression load higher than specimens not having non-slip device. The load transfers of lower non-slip devices of the standard method and the new method were similar in behavior, while the higher non-slip device of the new method showed higher ratio of load transfer than that of the standard method. And these two methods had nearly the same composite action and structural capacity caused by non-slip devices.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.33-36
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• 2007

The majority of fly ash pipes in thermal power stations use steel pipes. This makes frequent replacement inevitable due to severe abrasion near the hot and curved section of pipes. Recently, there have been efforts to prevent this abrasion with lining techniques using ceramic or basalt on the inner wall of the pipe. This study uses composite and anti-wear material to maximize the anti-abrasion effects on the hot section of the pipe. The thickness of the abrasion layer was determined by the abrasion ratio of material found through the experiment; the thickness of the reinforcement layer was determined by micromechanics. Experiments were conducted on epoxy resins to test for heat and abrasion. Anti-abrasion test using particle impingement was intended to recreate realistic conditions when abrasion occurs within the hot section of an actual pipe. This study analyzes the abrasion ratio obtained from both the specimen experiment and from on-site measurement and provides evidence that a combination of composites and anti-wear agent can be used to create a fly ash pipe that is lower in costs and higher in quality than what is used currently.