• Journal of Korean Society of Transportation
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• v.14 no.3
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• pp.155-172
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• 1996

This study is to analyze speed variation at merging section of successive entrance ramp and to suggest design criterion of ramp spacing at successive entrance ramp in urban area. The major findings are as follows ; (1) The relationship between the speed at merging section of successive entrance ramp and the distance from the merging point represents concave curve. (2) The 85 percentile speed(S) at outside lane (lane 1) is modeled S = 49.5 + 355.7(D/Q) - 0.94(D2/Q) + 6.78(D/AL2) where, D = Distance from merging point(m), Q = Lane 1 volume(vph) AL2 = Acceleration length at second entrance ramp(m) (3) The more traffic volume and the shorter acceleration length of the second entrance ramp, longer ramp terminal spacing is needed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.234-242
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• 1999

Flow phenomena such as the pressure transients Inside a high-speed railway tunnel and the Impulsive waves at the exit of the tunnel are closely associated with the characteristics of the entry compression wave, which is generated by a train entering the tunnel. Tunnel entrance hood may be an effective means for alleviating the Impulsive waves and pressure transients. The objective of the current work is to explore the effects of the train nose shape and the entrance hood on the characteristics of the entry compression wave. Numerical calculations using the method of characteristics were applied to one-dimensional, unsteady, compressible flow field with respect to high-speed railway/tunnel systems. Two types of the entrance hoods and various train nose shapes were employed to reveal their influences on the entry compression wave for a wide range of train speeds. The results showed that the entry compression wave length increases as the train nose becomes longer and the train speed becomes lower. The entry compression wave length in the tunnel with hood becomes longer than that of no hood. Maximum pressure gradient in the compression wavefront reduces by the entrance hood. The results of the current work provide useful data for the design of tunnel entrance hood.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.50-59
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• 1997

When a front head of train enters a tunnel at a high speed, compression wave is generated at tunnel entrance due to the confinement effect and propagated along the tunnel with sound of speed. The propagated compression wave is reflected at tunnel exit due to abrupt pressure change at passage. The reflected wave is expansion pressure wave. And when the rear head of train goes through the tunnel entrance, another expansion pressure wave is generated and propagated along the tunnel. The pressure drop occurs seriously around train when the two expansion pressure waves come cross on train in the tunnel. In order to reduce the pressure drop, the compression wave front must be controlled because the intensity and magnitude of pressure drop is nearly proportional to that of compression wave at tunnel entrance. This study relates to reduction of the pressure wave gradient with respect to tunnel entrance shape change with various kind of angle and rounding. The results show characteristics of wave propagation in tunnel, usefulness of characteristic curve to estimate proper time domain size in numerical study and measuring time in actual experiment. Also rounding is contributed to improve pressure wave front even if its radius is very small at tunnel entrance. In order to improve of pressure wave front at tunnel entrance, proper angle is prefered to rounding with big radius and an angle of around 14$^{\circ}$ is recommended according to this simulations, And it is expected to reduce additional pressure drop in tunnel when the location and the size of the internal space for attendant equipment are considered in advance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.1
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• pp.58-68
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• 1999

The entry compression wave, which forms at the entrance of a high-speed railway tunnel, is closely related to the pressure transients in the train/tunnel systems as well as an impulsive noise appearing at the exit of the tunnel. In order to alleviate such undesirable phenomena, some control strategies have been applied to the compression wave propagating inside the tunnel. The objective of the current work is to investigate the effect of tunnel entrance hoods on the entry compression wave at the vicinity of the tunnel entrance. Three types of entrance hoods were tested by the numerical method using the characteristics of method for a wide range of train speeds. The results show that the maximum pressure gradient of compression wave can be considerably reduced by the tunnel entrance hood. Optimum hood shape necessary to reduce the pressure transients and impulsive noise was found to be of an abrupt type hood with its cross-sectional area 2.5 times the tunnel area. It is believed that the current results are highly useful in predicting the effects of entrance hoods and in choosing the shape of proper hood.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.6
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• pp.758-765
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• 2001

Purpose of the present is to investigate the food configuration at a tunnel entrance for reducing the micro pressure wave that is generated according to train speed. Two configurations were examined for tunnel of 0.5 km length. The experimental results show that a slit cover hood installed at the entrance of the tunnel reduces the maximum micro pressure wave by 41.2%, and a configuration with a slit cover hood installed at the entrance and a 45$^{\circ}$slanted portal at the exit of the tunnel suppresses it by 47.7%.

• Journal of KSNVE
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• v.7 no.6
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• pp.959-966
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• 1997

In general, the booming noise intensity at tunnel exit is strongly related to the gradient of the compression wave front created by high speed train entering the tunnel. This paper presents some results in relation with the compression wave front produced when the high speed train enters a tunnel. Four kinds of tunnel entrance shape with real dimensions were studied to investigate the formation of compression wave front inside tunnel by train entering tunnel. Computations were carried out using three-dimensional compressible Euler equation with vanishing viscosity and conductivity of fluid. According to the results, the flow disturbances occured at tunnel entrance were eliminated by tunnel hood with same cross sectional area. The compression wave front is formed completely at 30-40m from tunnel entrance. The maximum pressure gradient of compression wave front is reduced by 29.8% for the inclined tunnel hood and reduced by 21.5% for the tunnel hood with holes at the top face with tunnel without hood. The length of the inclined hood is 15m and the length of the hood with holes is 20m.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.627-635
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• 1997

In general, the booming noise intensity at tunnel exit is strongly related to the gradient of the compression wave front created by high speed train entering the tunnel. This paper presents some results in relation with the compression wave front produced when the high speed train enters a tunnel. Four kinds of tunnel entrance shape with real dimensions were studied to investigate the formation of compression wave front inside tunnel by train entering tunnel. Computations were carried out using three-dimensional compressible Euler equation with vanishing viscosity and conductivity of fluid. According to the reslts, the flow disturbance occured at tunnel entrance were eliminated by tunnel hood with same cross sectional area. The compression wave front is formed completely at 30-40m from tunnel entrance. The maximum pressure gradient of compression wave front is reduced by 29.8% for the inclined tunnel hood and reduced by 21.5% for the tunnel hood with holes at the top face with tunnel without hood. The length of the inclined hood is 15m and the length of the hood with holes is 20m.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.3
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• pp.1-12
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• 2012

This paper aims at developing an active expressway entrance control effectiveness analysis tool which operators can utilize and manage traffic based on current traffic condition. For this, after identifying the current problems of tollgate-based entrance policy being used, a new set of decision element such as congestion index, decision criteria for congestion, and congestion management unit has been proposed together with the procedure of newly developed tollgate control policy. Three key parts developed are traffic condition identification module, tollgate metering module, and travel speed calculation module. Some measures of effectiveness were also identified and the newly developed effectiveness analysis tool produced better result. According to classification of traffic condition by reference speed as 80km/h, the improved tollgate entrance procedure increased 21.5% in average travel speed compared with Do-Nothing case and also increased 8.8% compared with current entrance control method.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.604-611
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• 1998

High-speed railway trains entering and leaving tunnels generate finite amplitude pressure wave which propagate back and forth along the tunnels, reflecting at the open ends of the tunnels and at other discontinuities such as ventilation shafts and the train themselves. In present day railways, the magnitudes of the pressure waves are much too small to cause structual damage, but they are a serious potential source of aural discomport for passengers on unsealed trains. Almost always do the pressure waves propagating along the tunnels lead to a hazardous impulse noise near the exit portal of the tunnel. In order to alleviate such undesirable phenomena, some control strategies have been applied to the compression wave propagating inside the tunnel. The objective of the current work is to investigate the effect of tunnel entrance hoods on the entry compression wave at the vicinity of the tunnel entrance. Three types of entrance hoods were tested by the numerical method using the characteristics of method for a wide range of train speeds. The results show that the maximum pressure gradient of compression wave can be considerably reduced by the tunnel entrance hood. Desirable hood shape for reduction of the pressure transients and impulse noise was found to be of abrupt type hood with its cross-sectional area 2.5times the tunnel area.

• Journal of Korean Society of Transportation
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• v.14 no.3
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• pp.75-90
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• 1996

The objective of study is to examine relationship between traffic flow characteristics of two lane entrance terminal and acceleration length, and to suggest the acceleration length by level of service. The relationship between the speed ratio and the distance from the ramp appeared to be a quadratic concave from. In the case of two lane entrance ramp, the acceleration length is suggested as 1.4~2.0 times longer than the acceleration length of one lane entrance ramp. It is also recommended that acceleration length for two lane entrance ramp should be designed according to the level of service at the right most lane (level of service A : 1.4 B : 1.6 C : 1.8 D : 2.0 times of the one lane entrance ramp acceleration length) on freeway.