• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.1
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• pp.1-13
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• 2010

A comparative study between a computation and an experiment has been conducted to predict the performance of a Pod type waterjet for cm amphibious wheeled vehicle. The Pod type waterjet has been chosen on the basis of the required specific speed of more than 2500. As the Pod type waterjet is an extreme type of axial flow type waterjet, theoretical as well as experimental works about Pod type waterjets are very rare. The main purpose of the present study is to validate and compare to the experimental results of the Pod type waterjet with the developed CFD in-house code based on the RANS equations. The developed code has been validated by comparing with the experimental results of the well-known turbine problem. The validation also extended to the flush type waterjet where the pressures along the duct surface and also velocities at nozzle area have been compared with experimental results. The Pod type waterjet has been designed and the performance of the designed waterjet system including duct, impeller and stator was analyzed by the previously mentioned m-house CFD Code. The pressure distributions and limiting streamlines on the blade surfaces were computed to confirm the performance of the designed waterjets. In addition, the torque and momentum were computed to find the entire efficiency and these were compared with the model test results. Measurements were taken of the flow rate at the nozzle exit, static pressure at the various sections along the duct and also the nozzle, revolution of the impeller, torque, thrust and towing forces at various advance speed's for the prediction of performance as well as for comparison with the computations. Based on these measurements, the performance was analyzed according to the ITTC96 standard analysis method. The full-scale effective and the delivered power of the wheeled vehicle were estimated for the prediction of the service speed. This paper emphasizes the confirmation of the ITTC96 analysis method and the developed analysis code for the design and analysis of the Pod type waterjet system.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.5
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• pp.380-387
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• 2014

Piper Alpha disaster drew attention to the damage likely to arise from explosions and fires on an offshore platform. And great concerns have been increased to prevent these hazards. Blast wall is one of the passive safety systems; it plays a key part of minimizing the consequences. However, a buckling due to explosion loads is a factor which can reduce the strength of blast wall. The buckling often occurs between web and flange at the center of blast wall. This study aims to find a solution for reinforcing its strength by installing a flat plate at the spot where the buckling occurs. First of all, ANSYS finite element method is adopted to numerically compute the structural resistance characteristic of blast wall by using a quasi-static approach. Sequentially, the impact response characteristics of blast wall are investigated the effect on thickness of flat plate by using ANSYS/LS-DYNA. Finally, pressure-impulse diagrams (P-I diagram) are presented to permit easy assessment of structural response characteristics of stiffened blast wall. In this study, effective use is made to increase structural intensity. of blast wall and acquired important insights have been documented.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.790-797
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• 2011

Hydrodynamic similarity was analyzed by employing scaling factor in three phase fluidized beds. The scaling factor was defined based on the holdups of gas, liquid and solid particles and effectivity volumetric flux of fluids between the two kinds of fluidized beds with different column diameter. The column diameter of one was 0.102 m and that of the other was 0.152 m. Filtered compressed air, tap water and glass bead of which density was 2,500 kg/$m^3$ were used as gas, liquid and solid phases, respectively. The individual phase holdups in three phase fluidized beds were determined by means of static pressure drop method. Effects of gas and liquid velocities and particle size on the scaling factors based on the holdups of each phase and effective volumetric flux of fluids were examined. The deviation of gas holdup between the two kinds of three phase fluidized beds decreased with increasing gas or liquid velocity but increased with increasing fluidized particle size. The deviation of liquid holdup between the two fluidized beds decreased with increasing gas or liquid velocity or size of fluidized solid particles. The deviation of solid holdup between the two fluidized beds increased with increasing gas velocity or particle size, however, decreased with increasing liquid velocity. The deviation of effective volumetric flux of fluids between the two fluidized beds decreased with increasing gas velocity or particle size, but increased with increasing liquid velocity. The scaling factor, which was defined in this study, could be effectively used to analyze the hydrodynamic similarity in three phase fluidized processes.

• Journal of the Korean Society of Physical Medicine
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• v.17 no.4
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• pp.103-111
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• 2022

PURPOSE: This study was performed to investigate the effects of the whole-body vibration exercise combined with ankle joint mobilization on the gait and balancing ability in patients with hemiplegic stroke. METHODS: A total of 19 patients at a rehabilitation hospital who had suffered a hemiplegic stroke were randomly assigned to the experimental group (whole-body vibration exercise combined with ankle joint mobilization, n=10) or control group (whole-body vibration exercise, n=9). All participants underwent 30 min of comprehensive rehabilitation therapy (5 × /week for 6 weeks). Additionally, the experimental group performed the whole body vibration exercise and ankle joint mobilization (15 minutes each, 30 minutes total, 3 × / week for 6 weeks). In the control group, only the whole- body vibration exercise was performed in the same manner and not the ankle joint mobilization. The gait and balancing abilities were measured before and after the 6-week training. RESULTS: Significant improvements were observed in the 10-m walk test, timed up-and-go (TUG) test, center of pressure (COP) path length, and COP path velocity in the experimental group (p < .05). The experimental group showed a larger decrease in the COP path length and velocity than the control group (COP path length, -10.27 mm vs. -3.67 mm, p < .05; COP path velocity, -.33 cm/sec vs. -.13 cm/sec, p < .05, respectively). CONCLUSION: The whole-body vibration exercise combined with ankle joint mobilization could be effective in improving the gait and balancing ability of stroke patients and could also be more effective for improving the static balance ability than the general whole-body vibration exercise alone.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.3
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• pp.135-140
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• 2019

Lattice towers and tubular steel poles have been commonly used for electrical power transmission in Korea. They are durable, structurally stable, simple and can easily be constructed in limited spaces. However, residents are opposed to construct transmission lattice towers in their areas because they are not visually attractive, and electrical field occur at the transmission lines. Underground transmissions have been used instead of the traditional towers to resolve these problems, however they are not cost effective to construct and run. Therefore, we have developed eco-friendly towers that are more attractive, well blending into the surrounding environment, and much more economical than underground transmissions. There are four categories of the eco-friendly electric transmission towers about design aspects. Firstly, there is decoration type such as tree tower and ensemble tower. Tree tower looks like actual trees with leaves and branches so it blends into surroundings. Ensemble towers were designed after pair of crane birds. Those towers have decoration features and art works. Structural examination and manufacturing this type would be very similar to the conventional transmission towers. Secondly, there is arm design type such as traditional tower. Design features are added to the existing towers. As partial design can be adoptable on these types, it can easily meet height regulations and attach to conventional lattice towers and tubular steel poles. Also, these towers are more economical than others. Third category is multipurpose type such as Sail Tower. These towers have simple pole or tubular structure with features which can be used as information message board, public relations and much more. This type will face greater wind pressure because of the area of the board, also visibility must take into consideration. Lastly, there is moulding type such as arc pylon. It is different shape to the conventional towers - lattice towers and tubular steel poles. Dramatic design changes have been adapted - from a hard and static tower to a soft and curved tower. These towers will well stand out in the field. However, structural examination and manufacturing this type would be difficult and costly. Also certain towers of this type would require scaffolding or false work to construct, which will result in limitations of the construction area. This paper shows KEPCO 154 kV Sail tower in detail. KEPCO 154 kV Sail tower that is included in fabrication of sample tower and tower testing has developed and the results are presented in this paper. We hope that sail tower is also considered as a solution to have public acceptance or to create a familiar atmosphere among towers and people in coastal area.