• Journal of computational fluids engineering
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• v.14 no.1
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• pp.35-44
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• 2009

To adequately analyze flows in pipe or duct network system, traditional node-based junction coupling methods require the junction loss which is specified by empirical or analytic correlations. In this paper, a new finite volume junction coupling method using a ghost junction cell is developed by considering the interchange of linear momentum as well as the important wall-effect at junction without requiring any correlation on the junction loss. Also, boundary treatment is modified to preserve the stagnation enthalpy across boundaries, such as pipe-end and the interface between junction and branch. Also, the computational accuracy and efficiency of the Godunov-type finite volume schemes are investigated by tracing the total mechanical energy of rapid transients due to sudden closure of valve at downstream end.

• The KSFM Journal of Fluid Machinery
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• v.13 no.6
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• pp.77-82
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• 2010

This study has conducted numerical analysis for lubrication system of transmission for commercial vehicle. The lubrication oil system in transmission can be applied to a large scale commercial vehicle which is over 15tons. The flow rate of lubricating oil has been obtained for each of branch port from the lubrication pipe. The results from numerical simulation are mainly suggested for the mass flow rate of lubrication oil in the rotating main shaft of transmission system. It has been found that the mass flow rate from oil hole increased with an rotating rate of main shaft. The flow characteristic from oil hole has been presented for the lubricating system in the manual transmission.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.12
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• pp.956-964
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• 2003

The paper describes the relationship between the eigenvalue branches and the corresponding flutter modes of cantilevered pipes with a tip mass conveying fluid. Governing equations of motion are derived by extended Hamilton's principle, and the numerical scheme using finite element method is applied to obtain the discretized equations. The flutter configurations of the pipes at the critical flow velocities are drawn graphically at every twelfth period to define the order of quasi-mode of flutter configuration. The critical mass ratios, at which the transference of the eigenvalue branches related to flutter takes place. are definitely determined. Also, in the case of haying internal damping, the critical tip mass ratios, at which the consistency between eigenvalue braches and quasi-modes occurs. are thoroughly obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.665-669
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• 2003

The paper deals with the relationship between the eigenvalue branches and the corresponding flutter modes of cantilevered pipes with a tip mass conveying fluid. Governing equations of motion are derived by extended Hamilton's principle, and the numerical scheme using finite element method is applied to obtain the discretized equations. The order of branches and unstable modes associated with flutter are defined in the stability maps of mass ratios of the pipe and the critical flow velocity. As a result, the relationship between the flutter related to the eigenvalue branches and the flutter modes are investigated thoroughly.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.473-476
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• 2000

Recently, many studies focus on mixed-mode fatigue-fracture characteristics of characteristics of materials. In order to reveal crack initiation and propagation mechanisms in combined -mode fatigue. This paper investigates the initiation and propagation behavior of the fatigue crack of the STS304 specimens under mixed mode loading conditions. moreover crack arrest and branch phenomena were analyzed with respect to the change do the angle of inclined loading. The relationship between the angle of inclined loading and the angle of branched crack was studied. A greate number of cycles are necessary to initiate a new crack from the initial crack. The direction of the new crack propagation is determined by MTS theory.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.11
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• pp.789-796
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• 2007

It has been noted, in case of the apartments in collective form, the drainage noise from cleaning of toilet causes many problems in the basement and adjacent rooms, mainly hampering the pleasant housing environment. The problems are increasingly raised by civil complaints with the public offices. Therefore, if the drainage noise generates when wash out of toilet bowl is grasped how the characteristics change according to the sorts of drainpipe, it is considered that the establishment of an effective sound insulation countermeasure could be possible when a civil petition against the drainage noise of apartment house is submitted hereafter. On such viewpoint, this study measured and analyzed the characteristics of drainage noise per the type of drainage pipe, according to KS A ISO $1996-1{\sim}3$, with the horizontal branch pipe and riser pipes in the drainage noise experiment chamber which has the characteristics of the anechoic room. In the result, the pipe type with excellent noise reduction function. The result of this study is considered to become available as fundamental data, to take actions on reduction of drainage noise of the ceiling piping method.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.2
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• pp.51-60
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• 2003

In the nuclear power plant, emergency core coolant system (ECCS) is furnished at reactor coolant system (RCS) in order to cool down high temperature water in case of emergency. However, in this coolant system, thermal stratification phenomenon can occur due to coolant leaking in the check valve. The thermal stratification produces excessive thermal stresses at the pipe wall so as to yield thermal fatigue crack (TFC) accident. In the present study, effects of turbulence penetration on the thermal stratification into T-branches with square cross-section in the modeled ECCS are analysed numerically. Standard k-$\varepsilon$ model is employed to calculate the Reynolds stresses in momentum equations. Results show that the length and strength of thermal stratification are primarily affected by the leak flow rate of coolant and the Reynolds number of duct. Turbulence penetration into the T-branch of ECCS shows two counteracting effects on the thermal stratification. Heat transport by turbulence penetration from main duct to leaking flow region may enhance thermal stratification while the turbulent diffusion may weaken it.

• Journal of Mechanical Science and Technology
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• v.20 no.7
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• pp.1030-1042
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• 2006

An experimental study has been performed to investigate the off-take phenomena at the header-feeder systems (horizontal header pipe with multiple feeder branch pipes) in a CANDU (CANadian Deuterium Uranium) reactor with the branch orientation varies ${\pm}36^{\circ}\;or\;{\pm}72^{\circ}$. In order to evaluate the applicability of the conventional correlations used in the safety analysis code, RELAP5-Mod3, the test facility is designed with the 1/2 scale of the. CANDU 6. It was found that the data set for the top, bottom and side branches are in a good agreement with the correlations used. However, for the specific angled branches, ${\pm}36^{\circ}\;and\;{\pm}72^{\circ}$, the onsets of off-take data and quality data showed large deviation with the conventional model inside RELAP5-MOD3. Furthermore, based on the uncertainty analysis, the conventional 2.5 power law needs to be modified. The present experimental data set can be useful for the construction of the general correlation considering the arbitrary branch orientation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.3
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• pp.239-245
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• 2003

In the nuclear power plant, emergency core coolant system (ECCS) is furnished at reactor coolant system (RCS) in order to cool down high temperature water in case of emergency. However, in this coolant system, thermal stratification phenomenon can occur due to coolant leaking in the check valve. The thermal stratification produces excessive thermal stresses at the pipe wall so as to yield thermal fatigue crack (TFC) accident. In the present study, effects of turbulence penetration on the thermal stratification into T-branches with square cross-section in the modeled ECCS are analysed numerically. $textsc{k}$-$\varepsilon$ model is employed to calculate the Reynolds stresses in momentum equations. Results show that the length and strength of thermal stratification are primarily affected by the leak flow rate of coolant and the Reynolds number of the main flow in the duct. Turbulence penetration into the T-branch of ECCS shows two counteracting effects on the thermal stratification. Heat transport by turbulence penetration from the main duct to leaking flow region may enhance thermal stratification while the turbulent diffusion may weaken it.

• Nuclear Engineering and Technology
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• v.36 no.2
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• pp.142-152
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• 2004

The liquid entrainment and vapor pull-through offtake model of RELAP5/MOD3 had been developed for SBLOCA (Small Break Loss of Coolant Accident). The RELAP5/MOD3 model for horizontal volumes accounts for the phase separation phenomena and computes the flux of mass and energy through a branch when stratified conditions occur in the horizontal pipe. In the case of CANDU reactor, this model should be used in the coolant flow of 95 feeders connected to the reactor header component under the horizontal stratification in header. The current RELAP5 model can treat the only 3 directions junctions; vertical upward, downward, and side oriented junctions, and thus improvements for the liquid entrainment and vapor pull-through model were needed for considering the exact angles. The RELAP5 off-take model was modified and generalized by considering the geometric effect of branching angles. Based on the previous experimental results, the critical height correlation was reconstructed by use of the branch line connection angle and validation analyses were also performed using SET. The new model can be applied to vertical upward, downward and angled branch, and the accuracy of the new correlations is more improved than that of RELAP5.