• Journal of the Korean Society for Railway
• /
• v.8 no.1
• /
• pp.51-56
• /
• 2005

A dynamic simulation program of a catenary-pantograph system including tunnel section and transient section is developed in this study. The simulation program can accommodate for the pantograph of two panheads and three d.o.f model. Using the developed program, the dynamic characteristics with a SCHUNK'S WBL 85-PANTOGRAPH are analyzed at the conventional TAEBAEK line and its tunnel section when the catenary system is supported by a tunnel bracket. The simulation results show that the variation of contact force md uplift displacement is allowable in general section and the entrance and exit of a tunnel, but the uplift displacement and the separation ratio within tunnel section is difficult to allow.

• Journal of Biomedical Engineering Research
• /
• v.21 no.3 s.61
• /
• pp.279-283
• /
• 2000

After ACL reconstruction. abrasion or wear of graft appeared frequently because of contact stresses between femoral tunnel and ACL. To minimize these problems. optimal shape of femoral tunnel is necessary. In this study. we evaluate friction force by degree of wear due to abrasion of soft tissue and develop 3-dimensional FEM model using ANSYS 5.5.1 version to analyze stress growths between femoral tunnel and ACL, We conclude that femoral tunnel angle must be slacked parallel to tunnel direction to minimize contact stress.

• Proceedings of the KSR Conference
• /
• 2004.06a
• /
• pp.767-772
• /
• 2004

A dynamic simulation program of a catenary-pantograph system including tunnel section and transient section is developed in this study. The simulation program can accommodate for the pantograph of two panheads and three d.o.f model. Using the developed program, the dynamic characteristics with a SCHUNK'S WBL 85-PANTOGRAPH is analyzed at the conventional TAEBAEK line and its tunnel section when the catenary system is supported by a tunnel bracket. The simulation results show that the variation of contact force and uplift displacement is allowable in general section and the entrance and exit of a tunnel, but the uplift displacement and the separation ratio within tunnel section is difficult to allow.

• Proceedings of the KSR Conference
• /
• 2011.05a
• /
• pp.70-77
• /
• 2011

When a train passes a conventional tunnel at high speed, an environmental noise issue arises by pressure variation and micro-pressure waves at the exit of the tunnel. It is known that this issue can be reduced by using dummy tunnel duct on the tunnel entrance. We studied the variances of micro-pressure waves at the exit of tunnel and pressure variation within the tunnel, by altering surface area and length of the dummy tunnel duct. For analyze this train-tunnel relation problem, axi-simmetric steady compressible flow solver was used. Changing the length of the dummy tunnel duct can adjust pressure variation, changing the surface area of the dummy tunnel duct can adjust volume and pressure variation of the micro-pressure wave. Thus, optimized surface area and length of the dummy tunnel duct can simultaneously reduce environmental noise pollution by micro-pressure wave and issues by the pressure variation.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.21 no.8
• /
• pp.983-995
• /
• 1997

As a high-speed train enters a tunnel, a compression wave is generated ahead of it due to the piston action of train. The compression waves propagate along the tunnel and reflect backward at the exit of tunnel. A complex wave phenomenon appears in the tunnel, because of the successive reflections of the pressure waves at the exit and entrance of tunnel. The pressure waves can give rise to large pressure transients which impose the fluctuating loads on the running train. It is highly needed that the pressure transients should be predicted to design the train body and to improve the comfort for the passengers in the train. In the present study, the pressure transients and aerodynamic drag for two-trains running in a tunnel were calculated numerically for a wide range of train speed, and compared with the results of the previous tunnel tests and calculations for one train. The present calculation results agreed with ones of the tunnel tests, and the mechanism of pressure transients was made clear.

• Proceedings of the KSR Conference
• /
• 1998.05a
• /
• pp.596-603
• /
• 1998

The entry compression wave, which is generated at the entrance of the tunnel, is almost always associated with the pressure transients in the tunnel as well as the impulse noise at the exit of the tunnel. It is highly required to design the train nose shape that can minimize such undesirable phenomena. The objective of the current work is to investigate the effects of the train nose shape on the entry compression wave. Numerical computations were applied to one-dimensional unsteady compressible flow in high-speed railway train/tunnel systems. A various shape of train noses were tested for a wide range of train speeds. The results showed that the strength of the entry compression wave is not influenced by the train nose shape, but the time variation of pressure in the entry compression wavefront is strongly related to the train nose shape. The current method of the characteristics was able to represent a desirable nose shape for various train speeds. Optimum nose shape was found to considerably reduce the maximum pressure gradient of the entry compression wave.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.11 no.4
• /
• pp.178-187
• /
• 2003

In this study, ventilation flow rate and pressure rise through a tunnel are simulated numerically using computational fluid dynamics (CFD) for various conditions such as roughness height of the surface of tunnel, swirl angle and hub/tip ratio of jet fan, and entrance and exit effects. By using a modified wall function, friction factor can be predicted with respect to the Moody chart within 10% of error for the circular pipe flow and 15% for the present tunnel. For more accurate design, the effect of the swirl angle and hub/tip ratio of jet fan, which is not included in the theoretical equation of pressure rise by jet fan needs to be considered.

• Journal of the Korean Society of Safety
• /
• v.34 no.2
• /
• pp.56-62
• /
• 2019

Secondary accident is common type of accident which occurs in Korean highway tunnels. Fatality rate of secondary accidents in highway tunnels is six time higher than primary accidents. Video type VMS is a new way of providing information to road users which was recently introduced by Korean government to prevent secondary accidents in highway tunnels. In this study we compared changes in driver's behavior when information is provided by Text type and Video Type VMS. In addition to analyze effects of secondary accident reduction, driving behavior was analyzed based on providing advance information by video type VMS at tunnel entrance. Analysis showed that both text type and video type VMS has similar effect on driver behavior. Video type VMS showed positive effect on driver's behavior to prevent secondary accident when information is provided 1km ahead of accident. Considering there results and the short-term memory characteristics of driver, it was determined that information should be provide at about 650m from the entrance of the tunnel. The results of this study are consistent with the requirement that VMS should be installed at least 500m ahead of tunnel and produce more accurate providing information points. 650m is also appropriate interval for providing information in tunnel to cope with an accident ahead.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.21 no.8
• /
• pp.963-972
• /
• 1997

As a high-speed train enters a tunnel, a compression wave is generated ahead of it due to the piston action of train. The compression waves propagate along the tunnel and reflect at the exit of tunnel. A complex wave phenomenon appears in the tunnel, because of the successive reflections of the pressure waves at the exit and entrance of tunnel. The pressure waves give rise to large pressure transients which impose the fluctuating loads on the running train. It is highly needed that the pressure transients should be predicted to design the train body and to improve the comfortableness of the passengers in the train. In the present study, the pressure transients were calculated numerically for a wide range of train speed and compared with the previous tunnel tests. The calculation results agreed with ones of the tunnel tests, and the mechanism of pressure transients was made clear.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.33 no.2
• /
• pp.115-125
• /
• 2023

Objectives: This study was conducted to measure the level of radon in the air at a highway tunnel construction site in a gneiss area using the New Austrian Tunneling Method (NATM) and to evaluate exposure levels by occupation. Methods: Radon concentrations in the air were measured using E-PERM at points 300 m, 600 m, and 900 m from the tunnel entrance during the excavation and waterproofing work inside the tunnel. In addition, radon concentrations were measured during external excavation to compare with the inside of the tunnel. Personal exposure levels for major occupations including tunnel workers, construction equipment operators, waterproofers, shotcrete workers, and safety and health managers who participated in the construction were estimated using radon concentration measured in the work process area and working hours by occupation. Results: As a result of a total of 77 radon measurements, the geometric mean (GM) concentration was 71.1 Bq/m³, and the maximum concentration was 127.3 Bq/m³, which was below the indoor air quality criteria. Radon concentration by process decreased in the order of the tunnel excavation process (GM= Bq/m³, GSD=1.2), waterproofing process (GM=73.35 Bq/m³, GSD=1.2), and outside excavating process (GM=45.28 Bq/m³, GSD=1.2). Processes inside the tunnel were significantly higher than outside excavating processes (p<0.05). There was no statistically significant difference in radon concentration measured inside by distance from the tunnel entrance, but the innermost point of the tunnel, 900 m (GM=79.24 Bq/m³, GSD=1.27), measured the highest. Conclusions: The occupation with the highest individual exposure to radon was tunnel worker (64.16 Bq/m³), followed by construction equipment driver (64.04 Bq/m³) and waterproofer (63.13 Bq/m³).