• Proceedings of the KSME Conference
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• 2002.08a
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• pp.95-98
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• 2002

Three-dimensional flow analyses for two different ratios of radius to height of sedimentation bed are implemented to evaluate the effect of blockage ratio of center feed wall and angle of distributor on sedimentation efficiency, and to find the optimal value of those parameters. Sedimentation efficiencies for three different shapes are compared with and without rotation speed. And then, five different combinations of blockage ratio of center feed wall and angle of distributor are compared It reveals that the effect of blockage ratio of center fled wall and angle of distributor is considerable to sedimentation efficiency while rotation effect can be neglected and $0.55 and 33^{\circ}$for blockage ratio of center food wall and angle of distributor, respectively, ive the best sedimentation efficiency.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.3
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• pp.211-221
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• 1982

Numerical analysis has been made on the heat transfer of two dimensional turbulent channel with a slat type blockage. Especially the effects of the height of slat and Reynolds number on the heat transfer characteristics of channel wall have been investigated. The methods of accelerating the convergence of the numerical solution of governing differential equation have been also examined. Line-by-line iterative method shows higher convergence rate than point-by-point iterative method for solution of both momentum equation and energy equation. The results show that the ratio of heat transfer coefficient of the wall near the blockage to that of the fully developed flow increase with increasing the ratio of blockage to channel height and decreasing the Reynolds number. These trends of variation of heat transfer coefficient with respect to the height of slat and Reynolds number agree with those of Sparrow's experiment on the pipe flow with slat type blockage.

• Wind and Structures
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• v.12 no.1
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• pp.49-61
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• 2009

A method is presented to estimate the form drag and the base pressure on a triangular cylinder in the presence of blockage effect. The Strouhal number, which is found to increase with the flow constriction experimentally by Ramamurthy & Ng (1973), may be decoupled from the blockage effect when re-defined by using the velocity at flow separation and a theoretical wake width. By incorporating this wake width into the momentum equation by Maskell (1963) for the confined flow, a relationship between the form drag and the base pressure is derived. Independently, the experimental data of surface pressure from Ramamurthy & Lee (1973) are found to be independent of the blockage effect when expressed in terms of a modified pressure coefficient involving the pressure at separation. Using the potential flow model by Parkinson & Jandali (1970) and its subsequent development in Yeung & Parkinson (2000) for the unconfined flow, a linear relation between the pressure at separation and the form drag is formulated. By solving the two equations simultaneously with a specified blockage ratio and an apex angle of the triangular cylinder, the predictions of the drag and the base pressure are in reasonable agreement with experimental data. A new theoretical relationship for the Strouhal number, pressure drag coefficient and base pressure proposed in this study allows the confinement effect to be appropriately taken into consideration. The present approach may be extended to three-dimensional bluff bodies.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.4 s.148
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• pp.431-439
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• 2006

Due to the limitation of size of the test section, blockage effects could not be avoided in the model test of yacht sails for common wind tunnels. In this paper, a numerical analysis is performed to investigate the blockage effects on the lift and drag forces measured from wind tunnel experiments for a 30 feet sloop yacht sail. Complex airflows around the jib and main sails including three-dimensional flow separations are calculated for various close-hauled conditions. It is found that the blockage of a wind tunnel changes the flow separation and consequently the lift and drag forces of the sails, especially the main sail, reduce and increase, respectively, due to the blockage effects.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3217-3228
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• 2021

Flow blockage of the fuel assembly in the lead-based fast reactor (LFR) may produce critical local spots, which will result in cladding failure and threaten reactor safety. In this study, the flow blockage characteristics were analyzed with the sub-channel analysis method, and the circumferentially-varied method was employed for considering the non-uniform distribution of circumferential temperature. The developed sub-channel analysis code SACOS-PB was validated by a heat transfer experiment in a blocked 19-rod bundle cooled by lead-bismuth eutectic. The deviations between the predicted coolant temperature and experimental values are within ±5%, including small and large flow blockage scenarios. And the temperature distributions of the fuel rod could be better simulated by the circumferentially-varied method for the small blockage scenario. Based on the validated code, the analysis of blockage characteristics was conducted. It could be seen from the temperature and flow distributions that a large blockage accident is more destructive compared with a small one. The sensitivity analysis shows that the closer the blockage location is to the exit, the more dangerous the accident is. Similarly, a larger blockage length will lead to a more serious case. And a higher exit temperature will be generated resulting from a higher peak coolant temperature of the blocked region. This work could provide a reference for the future design and development of the LFR.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.1
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• pp.39-46
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• 2008

The loss coefficient of the butterfly valve which allows partial opening of the valve at closed position and is applicable to the small-sized pipe system with the diameter of 1 inch was measured for the variation of the valve disk blockage ratio. Two different types of the valve disk configuration to adjust the blockage ratio were considered. One was the solid type valve disk of which the diameter was changed into the smaller size rather than the pipe diameter, and the other was the perforate type valve disk on which some holes were perforated. The results from two types of valve disk were compared to identify their characteristics in the loss coefficient distributions. The loss coefficient and the controllable angle of the valve disk were decreased exponentially with the decrease of the blockage ratio. In addition, the perforate valve disk had the effect on the higher loss coefficient rather than the solid type valve disk.

• Journal of the Korean Institute of Rural Architecture
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• v.6 no.2
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• pp.31-42
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• 2004

Although the coastal area of Jeju has already been developed, it has high pressure and demands for development continually increasing due to the increase of tourism and leisure activities. Therefore, the purpose of this study is to present objective guidance for the planning of the buildings on the seaside road with a view which have the largest impact on coastal landscape in order to enhance its visual quality. The results of this study are as follows : 1) It is chief element to make guidance for the use and planning of buildings in the conservation of the coastal landscape. 2) The D/H ratios which immediately influence an angle of elevation are different one another for the whole street. To ensure a sense of openness for the landscape, it is needed to maintain under $27^{\circ}$ angle of elevation, which demands 1~3 D/H ratio. 3) It is important to make 2.4 visual blockage ratio for whole street, but the actual condition is 4.48 ratio on average. To bring down the visual blockage ratio, the W/D ratio needs to be regulated. 4) Various techniques are also needed for lively building styles going with coastal landscape.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.98-113
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• 2016

A reactor vessel level monitoring system measures the water level in a reactor during normal operation and abnormal conditions. A drop in the water level can expose nuclear fuel, which may lead to fuel meltdown and radiation spread in accident conditions. A level monitoring system mainly consists of a sensing line and pressure transmitter. Over a period of time boron sediments or other impurities can clog the line which may degrade the accuracy of the monitoring system. The aim of this study is to determine blockage in a sensing line using the energy of the composite signal. An equivalent Pi circuit model is used to simulate blockages in the sensing line and the system's response is examined under different blockage levels. Composite signals obtained from the model and plant's unblocked and blocked channels are decomposed into six levels of details and approximations using a wavelet filter bank. The percentage of energy is calculated at each level for approximations. It is observed that the percentage of energy reduces as the blockage level in the sensing line increases. The results of the model and operational data are well correlated. Thus, in our opinion variation in the energy levels of approximations can be used as an index to determine the presence and degree of blockage in a sensing line.

• KIEAE Journal
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• v.11 no.2
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• pp.9-15
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• 2011

Many Korean palaces such as Deoksu Palace and Kyungbok Palace are located in downtown Seoul. Modern high-rise buildings around the palace have been the background scenery of traditional architecture in it. In this case, such landscapes mixed with traditional images and contemporary images can give a negative impression to visitors watching from inside the palace. In this study, we analysed the correlation between landscape image of Deoksu Palace and trees' view blockage of buildings around it with three independent variables. The first variable is completely blocked view of buildings around the palace by the trees. The second variable is half-blocked view of buildings around the palace by the trees. The third variable is the view of buildings around the palace that is not blocked by the trees. The analysis showed that there were some significant correlations between landscape image of Deoksu Palace and trees' view blockage of buildings around it. It also showed that the view blockage ratio by the trees has positive correlation with improvement of landscape image of the palace.

• Nuclear Engineering and Technology
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• v.41 no.6
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• pp.797-806
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• 2009

The Multichannel Analyzer for Transient and steady-state in Rod Array - Liquid Metal Reactor for Flow Blockage analysis (MATRA-LMR-FB) code for the analysis of a subchannel blockage has been developed and evaluated through several experiments. The current version of the code is improved here by the implementation of a distributed resistance model which accurately considers the effect of flow resistance on wire spacers, by the addition of a turbulent mixing model, and by the application of a hybrid scheme for low flow regions. Validation calculations for the MATRA-LMR-FB code were performed for Oak Ridge National Laboratory (ORNL) 19-pin tests with wire spacers and Karlsruhe 169-pin tests with grid spacers. The analysis of the ORNL 19-pin tests conducted using the code reveals that the code has sufficient predictive accuracy, within a range of 5 $^{\circ}C$, for the experimental data with a blockage. As for the results of the analyses, the standard deviation for the Karlsruhe 169-pin tests, 0.316, was larger than the standard deviation for the ORNL 19-pin tests, 0.047.