• The Korean Journal of Rheology
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• v.9 no.4
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• pp.140-150
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• 1997

• Fire Science and Engineering
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• v.22 no.3
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• pp.201-207
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• 2008

In this study, three Dimensional CFD simulations were carried out to investigate the effective smoke extraction system in bi-directional road tunnel fires using FLUENT. Characteristics of transverse system with big size extraction port or with uniform extraction port, semi-transverse system and longitudinal system for smoke extraction system were analyzed. Air velocity, port size, and operating method were used with variable. Distributions of smoke spread, CO was analyzed. As a result, the transverse ventilation system with big size port was found to be more effective than the uniform ports for bi-directional road tunnel.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.3
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• pp.326-338
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• 2017

The Vortex-induced Motions (VIM) phenomenon of semi-submersibles is relevant for the fatigue life of moorings and risers. Model tests regarding the VIM behavior of a semi-submersible with four square columns were conducted in order to investigate the effects of the current incidence and the aspect ratio of the immerged column. The experimental results show that the largest transverse amplitudes are around 70% of the column width at $30^{\circ}$ and $45^{\circ}$ incidences in a range of reduced velocities from 5 to 8 when the aspect ratio of the immerged column is 1.90. The largest yaw motion occurs at $0^{\circ}$ incidence with the peak value around $4.5^{\circ}$. Similar characteristics of the VIM response are observed for the semi-submersible with aspect ratios of 1.90 and 1.73. When the aspect ratio decreases 50% to 0.87, 30% decrease in the peak transverse amplitudes can be seen.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.517-532
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• 2017

The transverse ventilation system, commonly applied to urban tunnel, is necessary to be distributed with airflow uniformly. In this study, we developed a program that can optimize the opening ratio of ports to ensure ventilation performance of design criteria through a uniform airflow distribution even though ventilation interval becomes longer. And program's prediction performance was verified by comparison with TUNVEN DUCT program. For comparison, Semi-transverse ventilation system was applied. Both programs predicted a similar port size and air flow distribution, and the variation range of the calculated values was 11.71% and 1.36%, respectively. This program is very useful for port optimization design of transverse and semi-transverse ventilation system, because it is possible to analyze various tunnel lengths and supply/exhaust port installation conditions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.305-315
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• 2018

In this study, the ventilation characteristics and the relationships between the required ventilation flow rate and the ventilation system flow rate was investigated by numerical method for the optimum design of the transverse ventilation and semi-transverse ventilation system in road tunnels. The following results were obtained. In supply exhaust transverse ventilation system, the system supply-exhaust air flow rate is theoretically equal to the difference between the required ventilation flow rate and natural ventilation flow rate. However, it is shown that it increases by about 10% in the analysis results. And, in the case of the longitudinal air flow rate is increased by installed jet fans, ventilation system air flow rate is reduced. However, as the longitudinal air flow rate increases, the concentration of pollutants in the tunnel decreases, so the exhaust effect of pollutants decreases, and the effect of reducing the system air flow rate is decreased. In case of semi-transverse with only air supply, ventilation system air flow rate is equal to required ventilation air flow rate when tunnel inlet velocity is negative, but results is shown it is increased within about 13.3%. Also, it was found that ventilation effect can not be expected even if the jet fans are increased when the tunnel inlet velocity is negative.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.599-616
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• 2021

The semi-submersible with three circular columns is an original concept of efficient multifunctional platform, which can be used for marginal oil, gas field, and Floater of Wind Turbines (FOWT). However, under certain flow conditions, especially in uniform current with specific velocities, the eddies will alternatively form and drop behind columns, resulting in the fluctuating lift force and drag force. Consequently, the semi-submersible will subject to the Flow-Induced Motions (FIM). Based on the Detached Eddy Simulation (DES) method, the numerical studies were carried out to understand the FIM characteristics of the three-column semi-submersible at two different parameters, i.e., current incidences (0°, 30°, and 60°-incidences) and reduced velocities (4 ≤ U_r ≤ 14). The results indicate that the lock-in range of 6 ≤ U_r ≤ 10 for the transverse motions is presented, and the largest transverse non-dimensional nominal amplitude is observed at 60°-incidence, with a value of A_y/D = 0:481. The largest yaw amplitude A_yaw is around 3.0° at 0°-incidence in the range of 8 ≤ U_r ≤ 12. The motion magnitude is basically the same as that of a four-column semi-submersible. However, smaller responses are presented compared to those of the three-column systems revealing the mitigation effect of the pontoon on FIM.

• Journal of the Korean Society of Safety
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• v.21 no.2 s.74
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• pp.46-51
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• 2006

The smoke exhaust system is one of the effective systems to save lives when fire occurs underground. This study presents a complete analysis of effective smoke exhaust and smoke characteristics for a fire occurring with a transverse ventilation system use as a smoke exhaust system. The performance of the smoke management system was studied by computer modeling using FDS version 3.1. A fire size of 20MW was used for tunnel with balanced exhaust transverse ventilation. The smoke management design and the procedure as simulated in this study are also compliant to the tunnel construction and fire codes of Korea.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.2108-2114
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• 2000

The buckling of two elastic layers bonded to a semi-infinite substrate under a transverse compressive plane strain is investigated. Incremental deformation theory, which considers the effect of the initial stress on the incremental stress field, is employed to describe the buckling behavior of both two isotropic layers and the semi-infinite substrate. The problem is converted to an eigenvalue-eigenvector case, from which the critical buckling strain and the buckling wavelength are obtained. The results are presented on the effects of the layer geometries and material properties on the buckling behavior.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.369-374
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• 2000

The buckling of two elastic layers bonded to a semi-infinite substrate under a transverse compressive plane strain is investigated. Incremental deformation theory is employed to describe the buckling behavior of both two isotropic layers and the semi-infinite substrate. The problem is converted to an eigenvalue-eigenvector case, from which the critical buckling strain and the wavelength of the buckled shape are obtained. The results are presented on the effects of the layer geometries and material properties on the buckling behavior.

• Advances in aircraft and spacecraft science
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• v.10 no.3
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• pp.281-302
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• 2023

In this paper, bending analysis of exponentially varying functionally graded (FG) plate is presented using trigonometric shear deformation theory (TSDT) considering both transverse shear and normal deformation effects. The in-plane displacement field consists of sinusoidal functions in thickness direction to include transverse shear strains and transverse displacement include the effect of transverse normal strain using the cosine function in thickness coordinate. The governing equations and boundary conditions of the theory are derived using the virtual work principle. System of governing equations, for simply supported conditions, Navier's solution technique is used to obtain results. Plate material properties vary across thickness direction according to exponential distribution law. In the current theory, transverse shear stresses are distributed accurately through the plate thickness, hence obviates the need for a shear correction factor. TSDT results are compared with those from other theories to ensure the accuracy and effectiveness of the present theory. The current theory is in excellent agreement with the semi-analytical theory.